Publications

Publications in peer reviewed journals

38 Publications found
  • Nitrogen fertilization has a stronger effect on soil nitrogen-fixing bacterial communities than elevated atmospheric CO2

    Berthrong ST, Yeager CM, Gallegos-Graves L, Steven B, Eichorst SA, Jackson RB, Kuske CR
    2014 - Appl Environ Microbiol, 80: 3103-3112

    Abstract: 

    Biological nitrogen fixation is the primary supply of N to most ecosystems, yet there is considerable uncertainty about how N-fixing bacteria will respond to global change factors such as increasing atmospheric CO2 and N deposition. Using the nifH gene as a molecular marker, we studied how the community structure of N-fixing soil bacteria from temperate pine, aspen, and sweet gum stands and a brackish tidal marsh responded to multiyear elevated CO2conditions. We also examined how N availability, specifically, N fertilization, interacted with elevated CO2 to affect these communities in the temperate pine forest. Based on data from Sanger sequencing and quantitative PCR, the soil nifHcomposition in the three forest systems was dominated by species in the Geobacteraceae and, to a lesser extent, Alphaproteobacteria. The N-fixing-bacterial-community structure was subtly altered after 10 or more years of elevated atmospheric CO2, and the observed shifts differed in each biome. In the pine forest, N fertilization had a stronger effect on nifH community structure than elevated CO2 and suppressed the diversity and abundance of N-fixing bacteria under elevated atmospheric CO2 conditions. These results indicate that N-fixing bacteria have complex, interacting responses that will be important for understanding ecosystem productivity in a changing climate.

  • NanoSIMS combined with fluorescence microscopy as a tool for subcellular imaging of isotopically labeled platinum-based anticancer drugs

    Legin AA, Schintlmeister A, Jakupec MA, Galanski M, Lichtscheidl I, Wagner M, Keppler B
    2014 - Chem. Sci., 5: 3135-3143

    Abstract: 

    Multi-elemental, isotope selective nano-scale secondary ion mass spectrometry (NanoSIMS) combined with confocal laser-scanning microscopy was used to characterize the subcellular distribution of 15N-labeled cisplatin in human colon cancer cells. These analyses indicated predominant cisplatin colocalisation with sulfur-rich structures in both the nucleus and cytoplasm. Furthermore, colocalisation of platinum with phosphorus-rich chromatin regions was observed, which is consistent with its binding affinity to DNA as the generally accepted crucial target of the drug. Application of 15N-labeled cisplatin and subsequent measurement of the nitrogen isotopic composition and determination of the relative intensities of platinum and nitrogen associated secondary ion signals in different cellular compartments with NanoSIMS suggested partial dissociation of Pt–N bonds during the accumulation process, in particular within nucleoli at elevated cisplatin concentrations. This finding raises the question as to whether the observed intracellular dissociation of the drug has implications for the mechanism of action of cisplatin. Within the cytoplasm, platinum mainly accumulated in acidic organelles, as demonstrated by a direct combination of specific fluorescent staining, confocal laser scanning microscopy and NanoSIMS. Different processing of platinum drugs in acidic organelles might be relevant for their detoxification, as well as for their mode of action.

  • Improved axenization method reveals complexity of symbiotic associations between bacteria and acanthamoebae.

    Lagkouvardos I, Shen J, Horn M
    2014 - Environ Microbiol Rep., 6: 383-8

    Abstract: 

    Bacteria associated with free-living amoebae have attracted considerable attention because of their role in human disease and as models for studying endosymbiosis. However, the identification and analysis of such novel associations are hindered by the limitations of methods for isolation and axenization of amoebae. Here, we replaced the heat-inactivated Escherichia coli, which is typically used as food source during axenization, with a live E. coli tolC knockout mutant strain hypersensitive to antibiotics. Together with the addition of otherwise sublethal amounts of ampicillin, this approach tripled the success rate and reduced the time required for axenization by at least 3 days. Using this method for two environmental samples, 10 Acanthamoeba strains were isolated, seven of which contained bacterial symbionts. In three cases, amoebae harbouring two phylogenetically distinct symbionts were recovered, supporting a more widespread occurrence of multi-partner symbiotic associations among free-living amoebae.

  • Biology of a widespread uncultivated archaeon that contributes to carbon fixation in the subsurface.

    Probst A, Weinmaier T, Raymann K, Perras A, Emerson J, Rattei T, Wanner G, Klingl A, Berg I, Viehweger B, Yoshinaga M, Hinrichs K-U, Thomas B, Meck S, Auerbach A, Heise M, Schintlmeister A, Schmid M, Wagner M, Gribaldo S, Banfield J, Moissl-Eichinger C
    2014 - Nat Commun., 5: 5497
    SM1 Euryarchaeon

    Abstract: 

    Subsurface microbial life contributes significantly to biogeochemical cycling, yet it remains largely uncharacterized, especially its archaeal members. This 'microbial dark matter' has been explored by recent studies that were, however, mostly based on DNA sequence information only. Here, we use diverse techniques including ultrastuctural analyses to link genomics to biology for the SM1 Euryarchaeon lineage, an uncultivated group ofsubsurface archaea. Phylogenomic analyses reveal this lineage to belong to a widespread group of archaea that we propose to classify as a new euryarchaeal order ('Candidatus Altiarchaeales'). The representative, double-membraned species 'Candidatus Altiarchaeum hamiconexum' has an autotrophic metabolism that uses a not-yet-reported Factor420-free reductive acetyl-CoA pathway, confirmed by stable carbon isotopic measurements of archaeal lipids. Our results indicate that this lineage has evolved specific metabolic and structural features like nano-grappling hooks empowering this widely distributed archaeon to predominate anaerobic groundwater, where it may represent an important carbon dioxide sink.

  • Gene swapping in the dead zone.

    Petersen J, Dubilier N
    2014 - Elife, e04600

    Abstract: 

    Viruses can swap DNA between bacteria that live in regions of the oceans with little or no oxygen.

  • Bacteria from diverse habitats colonize and compete in the mouse gut

    Seedorf H, Griffin NW, Ridaura VK, Reyes A, Cheng J, Rey FE, Smith MI, Simon GM, Scheffrahn RH, Woebken D, Spormann AM, Van Treuren W, Ursell LK, Pirrung M, Robbins-Pianka A, Cantarel BL, Lombard V, Henrissat B, Knight R, Gordon JI.
    2014 - Cell, 159: 253-266
  • Substrate-specific development of thermophilic bacteria consortia using chemically pretreated switchgrass

    Eichorst SA, Joshua C, Sathitsuksanoh N, Singh S, Simmons BA, Singer SW
    2014 - Appl Environ Microbiol., 80: 7423-7432

    Abstract: 

    Microbial communities that deconstruct plant biomass have broad relevance in biofuel production and global carbon cycling. Biomass pretreatments reduce plant biomass recalcitrance for increased efficiency of enzymatic hydrolysis. We exploited these chemical pretreatments to study howthermophilic bacterial consortia adapt to deconstruct switchgrass (SG) biomass of varying compositions. Microbial communities were adapted to untreated, ammonium fiber expansion (AFEX)-pretreated, and ionic liquid (IL)-pretreated SG under aerobic, thermophilic conditions using green waste compost as the inoculum to study biomass deconstruction by microbial consortia. After microbial cultivation, gravimetric analysis of the residual biomass demonstrated that both AFEX- and IL-pretreatment enhanced the deconstruction of the SG biomass by approximately 2-fold. 2D-NMR experiments and acetyl bromide-reactive lignin analysis indicated that polysaccharide hydrolysis was the dominant process occurring during microbial biomass deconstruction and lignin remaining in the residual biomass was largely unmodified. SSU rRNA gene amplicon libraries revealed that although the dominant taxa across these chemical pretreatments were consistently represented by members of the Firmicutes, Bacteroidetes, and Deinococcus-Thermus phyla, the abundance of select OTUs varied suggesting adaptations to the different substrates. Combining the observations of differences in the community structure and the chemical and physical structure of the biomass, we hypothesize specific roles for individual community members in biomass deconstruction.

  • Genomic encyclopedia of bacteria and archaea: sequencing a myriad of type strains.

    Kyrpides NC, Hugenholtz P, Eisen JA, Woyke T, Göker, M, Parker CT, 45 other authors, Wagner M, Weinstock G, Weissenbach J, White O, Wang J, Zhang L, Zhou Y-G, Field D, Whitman WB, Garrity GM, Klenk H-P.
    2014 - PLoS Biol., 12(8):e1001920

    Abstract: 

    Microbes hold the key to life. They hold the secrets to our past (as the descendants of the earliest forms of life) and the prospects for our future (as we mine their genes for solutions to some of the planet's most pressing problems, from global warming to antibiotic resistance). However, the piecemeal approach that has defined efforts to study microbial genetic diversity for over 20 years and in over 30,000 genome projects risks squandering that promise. These efforts have covered less than 20% of the diversity of the cultured archaeal and bacterial species, which represent just 15% of the overall known prokaryotic diversity. Here we call for the funding of a systematic effort to produce a comprehensive genomic catalog of all cultured Bacteria and Archaea by sequencing, where available, the type strain of each species with a validly published name (currently∼11,000). This effort will provide an unprecedented level of coverage of our planet's genetic diversity, allow for the large-scale discovery of novel genes and functions, and lead to an improved understanding of microbial evolution and function in the environment.

  • Massive expansion of ubiquitination-related gene families within the Chlamydiae

    Domman D, Collingro A, Lagkouvardos I, Gehre L, Weinmaier T, Rattei T, Subtil A, Horn M
    2014 - Mol Biol Evol., 31: 2890-904

    Abstract: 

    Gene loss, gain, and transfer play an important role in shaping the genomes of all organisms; however, the interplay of these processes in isolated populations, such as in obligate intracellular bacteria, is less understood. Despite a general trend towards genome reduction in these microbes, our phylogenomic analysis of the phylum Chlamydiae revealed that within the family Parachlamydiaceae, gene family expansions have had pronounced effects on gene content. We discovered that the largest gene families within the phylum are the result of rapid gene birth-and-death evolution. These large gene families are comprised of members harboring eukaryotic-like ubiquitination-related domains, such as F-box and BTB-box domains, marking the largest reservoir of these proteins found among bacteria. A heterologous type III secretion system assay suggests that these proteins function as effectors manipulating the host cell. The large disparity in copy number of members in these families between closely related organisms suggests that nonadaptive processes might contribute to the evolution of these gene families. Gene birth-and-death evolution in concert with genomic drift might represent a previously undescribed mechanism by which isolated bacterial populations diversify.

  • Symbiont-driven sulfur crystal formation in a thiotrophic symbiosis from deep-sea hydrocarbon seeps.

    Eichinger I, Schmitz-Esser S, Schmid M, Fisher CR, Bright M
    2014 - Environ. Microbiol. Rep., 6: 364-72

    Abstract: 

    The siboglinid tubeworm Sclerolinum contortum symbiosis inhabits sulfidic sediments at deep-sea hydrocarbon seeps in the Gulf of Mexico. A single symbiont phylotype in the symbiont-housing organ is inferred from phylogenetic analyses of the 16S ribosomal ribonucleic acid (16S rRNA) gene and fluorescent in situ hybridization. The phylotype we studied here, and a previous study from an arctic hydrocarbon seep population, reveal identical 16S rRNA symbiont gene sequences. While sulfide is apparently the energy source for the symbionts (and ultimately the gutless host), both partners also have to cope with its toxicity. This study demonstrates abundant large sulfur crystals restricted to the trophosome area. Based on Raman microspectroscopy and energy dispersive X-ray analysis, these crystals have the same S8 sulfur configuration as the recently described small sulfurvesicles formed in the symbionts. The crystals reside adjacent to the symbionts in the trophosome. This suggests that their formation is either extra- or intracellular in symbionts. We propose that formation of these crystals provides both energy-storage compounds for the symbionts and serves thesymbiosis by removing excess toxic sulfide from host tissues. This symbiont-mediated sulfide detoxification may have been crucial for the establishment of thiotrophic symbiosis and continues to remain an important function of the symbionts.

  • Type I interferons have opposing effects during the emergence and recovery phases of colitis.

    Rauch I, Hainzl E, Rosebrock F, Heider S, Schwab C, Berry D, Stoiber D, Wagner M, Schleper C, Loy A, Urich T, Müller M, Strobl B, Kenner L, Decker T
    2014 - Eur J Immunol., 44: 2749-60

    Abstract: 

    The contribution of the innate immune system to inflammatory bowel disease (IBD) is under intensive investigation. Research in animal models has demonstrated that type I interferons (IFN-Is) protect from IBD. In contrast, studies of patients with IBD have produced conflicting results concerning the therapeutic potential of IFN-Is. Here, we present data suggesting that IFN-Is play dual roles as regulators of intestinal inflammation in dextran sodium sulfate (DSS)-treated C57BL/6 mice. Though IFN-Is reduced acute intestinal damage and the abundance ofcolitis-associated intestinal bacteria caused by treatment with a high dose of DSS, they also inhibited the resolution of inflammation after DSS treatment. IFN-Is played an anti-inflammatory role by suppressing the release of IL-1β from the colon MHC class II(+) cells. Consistently, IL-1 receptor blockade reduced the severity of inflammation in IFN-I receptor-deficient mice and myeloid cell-restricted ablation of the IFN-I receptor was detrimental. The proinflammatory role of IFN-Is during recovery from DSS treatment was caused by IFN-I-dependent cell apoptosis as well as an increase in chemokine production and infiltrating inflammatory monocytes and neutrophils. Thus, IFN-Is play opposing roles in specificphases of intestinal injury and inflammation, which may be important for guiding treatment strategies in patients.

  • Deciphering microbial interactions and detecting keystone species with co-occurrence networks

    Berry D, Widder S
    2014 - Front Microbiol, 5: 219

    Abstract: 

    Co-occurrence networks produced from microbial survey sequencing data are frequently used to identify interactions between community members. While this approach has potential to reveal ecological processes, it has been insufficiently validated due to the technical limitations inherent in studying complex microbial ecosystems. Here, we simulate multi-species microbial communities with known interaction patterns using generalized Lotka-Volterra dynamics. We then construct co-occurrence networks and evaluate how well networks reveal the underlying interactions and how experimental and ecological parameters can affect network inference and interpretation. We find that co-occurrence networks can recapitulate interaction networks under certain conditions, but that they lose interpretability when the effects of habitat filtering become significant. We demonstrate that networks suffer from local hot spots of spurious correlation in the neighborhood of hub species that engage in many interactions. We also identify topological features associated with keystone species in co-occurrence networks. This study provides a substantiated framework to guide environmental microbiologists in the construction and interpretation of co-occurrence networks from microbial survey datasets.

  • The giant ciliate Zoothamnium niveum and its thiotrophic epibiont Candidatus Thiobios zoothamnicoli: a model system to study interspecies cooperation

    Bright M, Espada-Hinojosa S, Lagkouvardos I, Volland JM
    2014 - Front Microbiol., 5: 145

    Abstract: 

    Symbioses between chemoautotrophic sulfur-oxidizing (thiotrophic) bacteria and protists or animals are among the most diverse and prevalent in the ocean. They are extremely difficult to maintain in aquaria and no thiotrophic symbiosis involving an animal host has ever been successfully cultivated. In contrast, we have cultivated the giant ciliate Zoothamnium niveum and its obligate ectosymbiont Candidatus Thiobios zoothamnicoli in small flow-through aquaria. This review provides an overview of the host and the symbiont and their phylogenetic relationships. We summarize our knowledge on the ecology, geographic distribution and life cycle of the host, on the vertical transmission of the symbiont, and on the cultivation of this symbiosis. We then discuss the benefits and costs involved in this cooperation compared with other thiotrophic symbioses and outline our view on the evolution and persistence of this byproduct mutualism.

  • Identification of Desulfobacterales as primary hydrogenotrophs in a complex microbial mat community

    Burow LC, Woebken D, Bebout BM, Marshall IPG, Singer SW, Pett-Ridge J, Prufert-Bebout L, Spormann AM, Weber PK, Hoehler TM
    2014 - Geobiology, 12: 221-230

    Abstract: 

    Hypersaline microbial mats have been shown to produce significant quantities of H2 under dark, anoxic conditions via cyanobacterial fermentation. This flux of a widely accessible microbial substrate has potential to significantly influence the ecology of the mat, and any consumption will affect the net efflux of H2 that might otherwise be captured as a resource. Here, we focus on H2 consumption in a microbial mat from Elkhorn Slough, California, USA, for which H2 production has been previously characterized. Active biologic H2 consumption in this mat is indicated by a significant time-dependent decrease in added H2 compared with a killed control. Inhibition of sulfate reduction, as indicated by a decrease in hydrogen sulfide production relative to controls, resulted in a significant increase in H2 efflux, suggesting that sulfate-reducing bacteria (SRB) are important hydrogenotrophs. Low methane efflux under these same conditions indicated that methanogens are likely not important hydrogenotrophs. Analyses of genes and transcripts that encode for rRNA or dissimilatory sulfite reductase, using both PCR-dependent and PCR-independent metatranscriptomic sequencing methods, demonstrated that Desulfobacterales are the dominant, active SRB in the upper, H2-producing layer of the mat (0-2 mm). This hypothesis was further supported by the identification of transcripts encoding hydrogenases derived from Desulfobacterales capable of H2 oxidation. Analysis of molecular data provided no evidence for the activity of hydrogenotrophic methanogens. The combined biogeochemical and molecular data strongly indicate that SRB belonging to the Desulfobacterales are the quantitatively important hydrogenotrophs in the Elkhorn Slough mat.

  • Spatial distribution analyses of natural phyllosphere-colonizing bacteria on Arabidopsis thaliana revealed by fluorescence in situ hybridization.

    Remus-Emsermann MNP, Lücker S, Müller DB, Potthoff E, Daims H, Vorholt JA
    2014 - Environ Microbiol, 16: 2329-2340

    Abstract: 

    Bacterial colonizers of the aerial parts of plants, or phyllosphere, have been identified on a number of different plants using cultivation-dependent and independent methods. However, the spatial distribution at the micrometer scale of different main phylogenetic lineages is not well documented and mostly based on fluorescence-tagged model strains. In this study, we developed and applied a spatial explicit approach that allowed the use of fluorescence in situ hybridization (FISH) to study bacterial phylloplane communities of environmentally grown Arabidopsis thaliana. We found on average 5.4 × 10(6) bacteria cm(-2) leaf surface and 1.5 × 10(8) bacteria g(-1) fresh weight. Furthermore, we found that the total biomass in the phylloplane was normally distributed. About 31% of the bacteria found in the phylloplane did not hybridize to FISH probes but exhibited infrared autofluorescence indicative for aerobic anoxygenic phototrophs. Four sets of FISH probes targeting Alphaproteobacteria, Betaproteobacteria, Actinobacteria and Bacteroidetes were sufficient to identify all other major contributors of the phylloplane community based on general bacterial probing. Spatial aggregation patterns were observed for all probe-targeted populations at distances up to 7 μm, with stronger tendencies to co-aggregate for members of the same phylogenetic group. Our findings contribute to a bottom-up description of leaf surface community composition.

  • The symbiotic intestinal ciliates and the evolution of their hosts

    Moon-van der Staay SY, van der Staay GWM, Michalowski T, Jouany JP, Pristas P, Javorsky P, Kisidayova S, Varadyova Z, McEwan NR, Newbold CJ, van Alen T, de Graaf R, Schmid M, Huynen MA, Hackstein JHP
    2014 - Eur J Protistol., 50: 166-73

    Abstract: 

    The evolution of sophisticated differentiations of the gastro-intestinal tract enabled herbivorous mammals to digest dietary cellulose and hemicellulose with the aid of a complex anaerobic microbiota. Distinctive symbiotic ciliates, which are unique to this habitat, are the largest representatives of this microbial community. Analyses of a total of 484 different 18S rRNA genes show that extremely complex, but related ciliate communities can occur in the rumen of cattle, sheep, goats and red deer (301 sequences). The communities in the hindgut of equids (Equus caballus, Equus quagga), and elephants (Elephas maximus, Loxodonta africanus; 162 sequences), which are clearly distinct from the ruminant ciliate biota, exhibit a much higher diversity than anticipated on the basis of their morphology. All these ciliates from the gastro-intestinal tract constitute a monophyletic group, which consists of two major taxa, i.e. Vestibuliferida and Entodiniomorphida. The ciliates from the evolutionarily older hindgut fermenters exhibit a clustering that is specific for higher taxa of their hosts, as extant species of horse and zebra on the one hand, and Africa and Indian elephant on the other hand, share related ciliates. The evolutionary younger ruminants altogether share the various entodiniomorphs and the vestibuliferids from ruminants.

  • Fermentation couples Chloroflexi and sulfate-reducing bacteria to Cyanobacteria in hypersaline microbial mats

    Lee JZ, Burow LC, Woebken D, Everroad RC, Kubo MD, Spormann AM, Weber PK, Pett-Ridge J, Bebout BM, Hoehler TM
    2014 - Front Microbiol., 5:61

    Abstract: 

    Past studies of hydrogen cycling in hypersaline microbial mats have shown an active nighttime cycle, with production largely from Cyanobacteriaand consumption from sulfate-reducing bacteria (SRB). However, the mechanisms and magnitude of hydrogen cycling have not been extensively studied. Two mats types near Guerrero Negro, Mexico-permanently submerged Microcoleus microbial mat (GN-S), and intertidal Lyngbya microbialmat (GN-I)-were used in microcosm diel manipulation experiments with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), molybdate, ammonium addition, and physical disruption to understand the processes responsible for hydrogen cycling between mat microbes. Across microcosms, H2 production occurred under dark anoxic conditions with simultaneous production of a suite of organic acids. H2 production was not significantly affected by inhibition of nitrogen fixation, but rather appears to result from constitutive fermentation of photosynthetic storage products by oxygenic phototrophs. Comparison to accumulated glycogen and to CO2 flux indicated that, in the GN-I mat, fermentation released almost all of the carbon fixed via photosynthesis during the preceding day, primarily as organic acids. Across mats, although oxygenic and anoxygenic phototrophs were detected, cyanobacterial [NiFe]-hydrogenase transcripts predominated. Molybdate inhibition experiments indicated that SRBs from a wide distribution of DsrA phylotypes were responsible for H2 consumption. Incubation with (13)C-acetate and NanoSIMS (secondary ion mass-spectrometry) indicated higher uptake in both Chloroflexi and SRBs relative to other filamentous bacteria. These manipulations and diel incubations confirm thatCyanobacteria were the main fermenters in Guerrero Negro mats and that the net flux of nighttime fermentation byproducts (not only hydrogen) was largely regulated by the interplay between Cyanobacteria, SRBs, and Chloroflexi.

  • Nitrolancea hollandica gen. nov., sp. nov., a chemolithoautotrophic nitrite-oxidizing bacterium isolated from a bioreactor belonging to the phylum Chloroflexi

    Sorokin DY, Vejmelkova D, Lücker S, Streshinskaya GM, Rijpstra I, Sinninghe Damsté J, Kleerebezem R, Van Loosdrecht M, Muyzer G, Daims H
    2014 - Int J Syst Evol Microbiol, 64: 1859-1865

    Abstract: 

    A novel nitrite-oxidizing bacterium (NOB), strain Lb(T), was isolated from a nitrifying bioreactor with a high loading of ammonium bicarbonate in a mineral medium with nitrite as the energy source. The cells were oval (lancet-shaped) rods with pointed edges, non-motile, Gram-positive (by staining and from the cell wall structure) and non-spore-forming. Strain Lb(T) was an obligately aerobic, chemolitoautotrophic NOB, utilizing nitrite or formate as the energy source and CO2 as the carbon source. Ammonium served as the only source of assimilated nitrogen. Growth with nitrite was optimal at pH 6.8-7.5 and at 40 °C (maximum 46 °C). The membrane lipids consisted of C20 alkyl 1,2-diols with the dominant fatty acids being 10MeC18 and C(18 : 1)ω9. The peptidoglycan lacked meso-DAP but contained ornithine and lysine. The dominant lipoquinone was MK-8. Phylogenetic analyses of the 16s rRNA gene sequence placed strain Lb(T) into the class Thermomicrobia of the phylum Chloroflexiwith Sphaerobacter thermophilus as the closest relative. On the basis of physiological and phylogenetic data, it is proposed that strain Lb(T) represents a novel species of a new genus, with the suggested name Nitrolancea hollandica gen. nov., sp. nov. The type strain of the type species is Lb(T) ( = DSM 23161(T) = UNIQEM U798(T)).

  • Dual symbiosis with co-occurring sulfur-oxidizing symbionts in vestimentiferan tubeworms from a Mediterranean hydrothermal vent.

    Zimmermann J, Lott C, Weber M, Ramette A, Bright M, Dubilier N, Petersen JM
    2014 - Environ. Microbiol., 12: 3638-56

    Abstract: 

    Vestimentiferan Tws colonize hydrothermal vents and cold seeps worldwide. They lack a digestive system and gain nutrition from endosymbiotic sulfur-oxidizing bacteria. It is currently assumed that vestimentiferan Tws harbour only a single endosymbiont type. A few studies found indications for additional symbionts, but conclusive evidence for a multiple symbiosis is still missing. We investigated Tws from Marsili Seamount, a hydrothermal vent in the Mediterranean Sea. Molecular and morphological analyses identified the Tws as Lamellibrachia anaximandri. 16S ribosomal RNA clone libraries revealed two distinct gammaproteobacterial phylotypes that were closely related to sequences from other Lamellibrachia symbionts. Catalysed reporter deposition fluorescence in situ hybridization with specific probes showed that these sequences are from two distinct symbionts. We also found two variants of key genes for sulfur oxidation and carbon fixation, suggesting that both symbiont types are autotrophic sulfur oxidizers. Our results therefore show that vestimentiferans can host multiple co-occurring symbiont types. Statistical analyses of vestimentiferan symbiont diversity revealed that host genus, habitat type, water depth and geographic region together accounted for 27% of genetic diversity, but only water depth had a significant effect on its own. Phylogenetic analyses showed a clear grouping of sequences according to depth, thus confirming the important role water depth played in shaping vestimentiferan symbiont diversity.

  • Life in an unusual intracellular niche: a bacterial symbiont infecting the nucleus of amoebae

    Schulz F, Lagkouvardos I, Wascher F, Aistleitner K, Kostanjšek R, Horn M
    2014 - ISME J., 8: 1634-44

    Abstract: 

    Amoebae serve as hosts for various intracellular bacteria, including human pathogens. These microbes are able to overcome amoebal defense mechanisms and successfully establish a niche for replication, which is usually the cytoplasm. Here, we report on the discovery of a bacterialsymbiont that is located inside the nucleus of its Hartmannella sp. host. This symbiont, tentatively named 'Candidatus Nucleicultrix amoebiphila', is only moderately related to known bacteria (∼90% 16S and 23S rRNA sequence similarity) and member of a novel clade of protist symbionts affiliated with the Rickettsiales and Rhodospirillales. Screening of 16S rRNA amplicon data sets revealed a broad distribution of these bacteria in freshwater and soil habitats. 'Candidatus Nucleicultrix amoebiphila' traffics within 6 h post infection to the host nucleus. Maximum infection levels are reached after 96-120 h, at which time point the nucleus is pronouncedly enlarged and filled with bacteria. Transmission of the symbionts occurs vertically upon host cell division but may also occur horizontally through host cell lysis. Although we observed no impact on the fitness of the original Hartmannella sp. host, the bacteria are rather lytic for Acanthamoeba castellanii. Intranuclear symbiosis is an exceptional phenomenon, and amoebae represent an ideal model system to further investigate evolution and underlying molecular mechanisms of these unique microbial associations.

  • Chlamydial metabolism revisited: interspecies metabolic variability and developmental stage-specific physiologic activities

    Omsland A, Sixt BS, Horn M, Hackstadt T
    2014 - FEMS Microbiol Rev., 38: 779-801

    Abstract: 

    Chlamydiae are a group of obligate intracellular bacteria comprising important human and animal pathogens as well as symbionts of ubiquitous protists. They are characterized by a developmental cycle including two main morphologically and physiologically distinct stages, the replicating reticulate body and the infectious nondividing elementary body. In this review, we reconstruct the history of studies that have led to our current perception of chlamydial physiology, focusing on their energy and central carbon metabolism. We then compare the metabolic capabilities of pathogenic and environmental chlamydiae highlighting interspecies variability among the metabolically more flexible environmental strains. We discuss recent findings suggesting that chlamydiae may not live as energy parasites throughout the developmental cycle and that elementary bodies are not metabolically inert but exhibit metabolic activity under appropriate axenic conditions. The observed host-free metabolic activity of elementary bodies may reflect adequate recapitulation of the intracellular environment, but there is evidence that this activity is biologically relevant and required for extracellular survival and maintenance of infectivity. The recent discoveries call for a reconsideration of chlamydial metabolism and future in-depth analyses to better understand how species- and stage-specific differences in chlamydial physiology may affect virulence, tissue tropism, and host adaptation.

  • The gill chamber epibiosis of deep-sea shrimp Rimicaris exoculata: an in-depth metagenomic investigation and discovery of Zetaproteobacteria.

    Jan C, Petersen JM, Werner J, Teeling H, Huang S, Glöckner FO, Golyshina OV, Dubilier N, Golyshin PN, Jebbar M, Cambon-Bonavita MA
    2014 - Environ. Microbiol., 9: 2723-38

    Abstract: 

    The gill chamber of deep-sea hydrothermal vent shrimp Rimicaris exoculata hosts a dense community of epibiotic bacteria dominated by filamentous Epsilonproteobacteria and Gammaproteobacteria. Using metagenomics on shrimp from the Rainbow hydrothermal vent field, we showed that both epibiont groups have the potential to grow autotrophically and oxidize reduced sulfur compounds or hydrogen with oxygen or nitrate. For carbon fixation, the Epsilonproteobacteria use the reductive tricarboxylic acid cycle, whereas the Gammaproteobacteria use the Calvin-Benson-Bassham cycle. Only the epsilonproteobacterial epibionts had the genes necessary for producing ammonium. This ability likely minimizes direct competition between epibionts and also broadens the spectrum of environmental conditions that the shrimp may successfully inhabit. We identified genes likely to be involved in shrimp-epibiont interactions, as well as genes for nutritional and detoxification processes that might benefit the host. Shrimp epibionts at Rainbow are often coated with iron oxyhydroxides, whose origin is intensely debated. We identified 16S rRNA sequences and functional genes affiliated with iron-oxidizing Zetaproteobacteria, which indicates that biological iron oxidation might play a role in forming these deposits. Fluorescence in situ hybridizations confirmed the presence of active Zetaproteobacteria in the R. exoculata gill chamber, thus providing the first evidence for a Zetaproteobacteria-invertebrate association.

  • The pine bark adelgid Pineus strobi contains two novel bacteriocyte-associated gammaproteobacterial symbionts

    Toenshoff ER, Szabó G, Gruber D, Horn M
    2014 - Appl Environ Microbiol., 80: 878-85

    Abstract: 

    Bacterial endosymbionts of the pine bark adelgid, Pineus strobi (Insecta: Hemiptera: Adelgidae), were investigated using transmission electron microscopy, 16S and 23S rRNA-based phylogeny, and fluorescence in situ hybridization. Two morphologically different symbionts affiliated with the Gammaproteobacteria were present in distinct bacteriocytes. One of them ("Candidatus Annandia pinicola") is most closely related to an endosymbiont of Adelges tsugae, suggesting that they originate from a lineage already present in ancient adelgids before the hosts diversified into the two major clades, Adelges and Pineus. The other P. strobi symbiont ("Candidatus Hartigia pinicola") represents a novel symbiont lineage in members of the Adelgidae. Our findings lend further support for a complex evolutionary history of the association of adelgids with a phylogenetically diverse set of bacterial symbionts.

  • Tracing the primordial Chlamydiae: extinct parasites of plants?

    Subtil A, Collingro A, Horn M
    2014 - Trends Plant Sci., 19: 36-43

    Abstract: 

    Chlamydiae are obligate intracellular bacteria found as symbionts and pathogens in a wide range of eukaryotes, including protists, invertebrates, and vertebrates. It was recently proposed that an ancient chlamydial symbiont facilitated the establishment of primary plastids in a tripartite symbiosis with cyanobacteria and early eukaryotes. In this review, we summarize recent advances in understanding of the lifestyle and the evolutionary history of extant Chlamydiae. We reconstruct and describe key features of the ancient chlamydial symbiont. We propose that it was already adapted to an intracellular lifestyle before the emergence of Archaeplastida, and that several observations are compatible with an essential contribution of Chlamydiae to the evolution of algae and plants.

  • Signature protein of the PVC superphylum

    Lagkouvardos I, Jehl MA, Rattei T, Horn M
    2014 - Appl Environ Microbiol., 80: 440-5

    Abstract: 

    The phyla Planctomycetes, Verrucomicrobia, Chlamydiae, Lentisphaerae, and "Candidatus Omnitrophica (OP3)" comprise bacteria that share an ancestor but show highly diverse biological and ecological features. Together, they constitute the PVC superphylum. Using large-scale comparative genome sequence analysis, we identified a protein uniquely shared among all of the known members of the PVC superphylum. We provide evidence that this signature protein is expressed by representative members of the PVC superphylum. Its predicted structure, physicochemical characteristics, and overexpression in Escherichia coli and gel retardation assays with purified signature protein suggest a housekeeping function with unspecific DNA/RNA binding activity. Phylogenetic analysis demonstrated that the signature protein is a suitable phylogenetic marker for members of the PVC superphylum, and the screening of published metagenome data indicated the existence of additional PVC members. This study provides further evidence of a common evolutionary history of the PVC superphylum and presents a unique case in which a single protein serves as an evolutionary link among otherwise highly diverse members of major bacterial groups.

  • Architecture and host interface of environmental chlamydiae revealed by electron cryotomography

    Pilhofer M, Aistleitner K, Ladinsky MS, König L, Horn M, Jensen GJ
    2014 - Environ Microbiol., 16: 417-29

    Abstract: 

    Chlamydiae comprise important pathogenic and symbiotic bacteria that alternate between morphologically and physiologically different life stages during their developmental cycle. Using electron cryotomography, we characterize the ultrastructure of the developmental stages of threeenvironmental chlamydiae: Parachlamydia acanthamoebae, Protochlamydia amoebophila and Simkania negevensis. We show that chemical fixation and dehydration alter the cell shape of Parachlamydia and that the crescent body is not a developmental stage, but an artefact of conventional electron microscopy. We further reveal type III secretion systems of environmental chlamydiae at macromolecular resolution and find support for a chlamydial needle-tip protein. Imaging bacteria inside their host cells by cryotomography for the first time, we observe marked differences in inclusion morphology and development as well as host organelle recruitment between the three chlamydial organisms, with Simkania inclusions being tightly enveloped by the host endoplasmic reticulum. The study demonstrates the power of electron cryotomographyto reveal structural details of bacteria-host interactions that are not accessible using traditional methods.

  • High-fat diet alters gut microbiota physiology in mice

    Daniel H, Moghaddas Gholami A, Berry D, Desmarchelier C, Hahne H, Loh G, Mondot S, Lepage P, Rothballer M, Walker A, Böhm C, Wenning M, Wagner M, Blaut M, Schmitt-Kopplin P, Kuster B, Haller D, Clavel T
    2014 - ISME J., 8: 295-308

    Abstract: 

    The intestinal microbiota is known to regulate host energy homeostasis and can be influenced by high-calorie diets. However, changes affecting the ecosystem at the functional level are still not well characterized. We measured shifts in cecal bacterial communities in mice fed a carbohydrate orhigh-fat (HF) diet for 12 weeks at the level of the following: (i) diversity and taxa distribution by high-throughput 16S ribosomal RNA gene sequencing; (ii) bulk and single-cell chemical composition by Fourier-transform infrared- (FT-IR) and Raman micro-spectroscopy and (iii) metaproteome and metabolome via high-resolution mass spectrometry. High-fat diet caused shifts in the diversity of dominant gut bacteria and altered the proportion of Ruminococcaceae (decrease) and Rikenellaceae (increase). FT-IR spectroscopy revealed that the impact of the diet on cecal chemical fingerprints is greater than the impact of microbiota composition. Diet-driven changes in biochemical fingerprints of members of the Bacteroidales and Lachnospiraceae were also observed at the level of single cells, indicating that there were distinct differences in cellular composition of dominant phylotypes under different diets. Metaproteome and metabolome analyses based on the occurrence of 1760 bacterial proteins and 86 annotated metabolites revealed distinct HF diet-specific profiles. Alteration of hormonal and anti-microbial networks, bile acid and bilirubin metabolism and shifts towards amino acid and simple sugars metabolism were observed. We conclude that a HF diet markedly affects the gut bacterial ecosystem at the functional level.

  • Integrating metagenomic and amplicon databases to resolve the phylogenetic and ecological diversity of the Chlamydiae.

    Lagkouvardos I, Weinmaier T, Lauro FM, Cavicchioli R, Rattei T, Horn M
    2014 - ISME J, 1: 115-25

    Abstract: 

    In the era of metagenomics and amplicon sequencing, comprehensive analyses of available sequence data remain a challenge. Here we describe an approach exploiting metagenomic and amplicon data sets from public databases to elucidate phylogenetic diversity of defined microbial taxa. We investigated the phylum Chlamydiae whose known members are obligate intracellular bacteria that represent important pathogens of humans and animals, as well as symbionts of protists. Despite their medical relevance, our knowledge about chlamydial diversity is still scarce. Most of the nine known families are represented by only a few isolates, while previous clone library-based surveys suggested the existence of yet uncharacterized members of this phylum. Here we identified more than 22,000 high quality, non-redundant chlamydial 16S rRNA gene sequences in diverse databases, as well as 1900 putative chlamydial protein-encoding genes. Even when applying the most conservative approach, clustering of chlamydial 16S rRNA gene sequences into operational taxonomic units revealed an unexpectedly high species, genus and family-level diversity within the Chlamydiae, including 181 putative families. These in silico findings were verified experimentally in one Antarctic sample, which contained a high diversity of novel Chlamydiae. In our analysis, the Rhabdochlamydiaceae, whose known members infect arthropods, represents the most diverse and species-rich chlamydial family, followed by the protist-associated Parachlamydiaceae, and a putative new family (PCF8) with unknown host specificity. Available information on the origin of metagenomic samples indicated that marine environments contain the majority of the newly discovered chlamydial lineages, highlighting this environment as an important chlamydial reservoir.

  • Thermophilic biological nitrogen removal in industrial wastewater treatment.

    Lopez-Vazquez CM, Kubare M, Saroj DP, Chikamba C, Schwarz J, Daims H, Brdjanovic D
    2014 - Appl Microbiol Biotechnol, 98: 945-956

    Abstract: 

    Nitrification is an integral part of biological nitrogen removal processes and usually the limiting step in wastewater treatment systems. Since nitrification is often considered not feasible at temperatures higher than 40 °C, warm industrial effluents (with operating temperatures higher than 40 °C) need to be cooled down prior to biological treatment, which increases the energy and operating costs of the plants for cooling purposes. This study describes the occurrence of thermophilic biological nitrogen removal activity (nitritation, nitratation, and denitrification) at a temperature as high as 50 °C in an activated sludge wastewater treatment plant treating wastewater from an oil refinery. Using a modified two-step nitrification-two-step denitrification mathematical model extended with the incorporation of double Arrhenius equations, the nitrification (nitrititation and nitratation) and denitrification activities were described including the cease in biomass activity at 55 °C. Fluorescence in situ hybridization (FISH) analyses revealed that Nitrosomonas halotolerant and obligatehalophilic and Nitrosomonas oligotropha (known ammonia-oxidizing organisms) and Nitrospira sublineage II (nitrite-oxidizing organism (NOB)) were observed using the FISH probes applied in this study. In particular, this is the first time that Nitrospira sublineage II, a moderatedly thermophilic NOB, is observed in an engineered full-scale (industrial) wastewater treatment system at temperatures as high as 50 °C. These observations suggest that thermophilic biological nitrogen removal can be attained in wastewater treatment systems, which may further contribute to the optimization of the biological nitrogen removal processes in wastewater treatment systems that treat warm wastewaterstreams.

  • Growth of nitrite-oxidizing bacteria by aerobic hydrogen oxidation

    Koch H, Galushko A, Albertsen M, Schintlmeister A, Gruber-Dorninger C, Lücker S, Pelletier E, Le Paslier D, Spieck E, Richter A, Nielsen PH, Wagner M, Daims H
    2014 - Science, 345: 1052-1054

    Abstract: 

    The bacterial oxidation of nitrite to nitrate is a key process of the biogeochemical nitrogen cycle. Nitrite-oxidizing bacteria are considered a highly specialized functional group, which depends on the supply of nitrite from other microorganisms and whose distribution strictly correlates with nitrification in the environment and in wastewater treatment plants. On the basis of genomics, physiological experiments, and single-cell analyses, we show that Nitrospira moscoviensis, which represents a widely distributed lineage of nitrite-oxidizing bacteria, has the genetic inventory to utilizehydrogen (H2) as an alternative energy source for aerobic respiration and grows on H2 without nitrite. CO2 fixation occurred with H2 as the sole electron donor. Our results demonstrate a chemolithoautotrophic lifestyle of nitrite-oxidizing bacteria outside the nitrogen cycle, suggesting greater ecological flexibility than previously assumed.

  • Removal of pharmaceuticals and personal care products during water recycling: microbial community structure and effects of substrate concentration.

    Oneisis-Barry K, Berry D, Proscher J, Sivakumar IKA, Bouwer E
    2014 - Appl Environ Microbiol., 80: 2440-50

    Abstract: 

    Many pharmaceuticals and personal care products (PPCPs) have been shown to be biotransformed in water treatment systems. However, little research exists on the effect of initial PPCP concentration on PPCP biotransformation or on the microbial communities treating impacted water. In this study, biological PPCP removal at various concentrations was assessed using laboratory columns inoculated with wastewater treatment plant effluent. Pyrosequencing was used to examine microbial communities in the columns and in soil from a soil aquifer treatment (SAT; a method ofwater treatment prior to reuse) site. Laboratory columns were supplied with different concentrations (0.25, 10, 100, or 1,000 μg liter(-1)) of each of 15 PPCPs. Five PPCPs (4-isopropyl-3-methylphenol [biosol], p-chloro-m-xylenol, gemfibrozil, ketoprofen, and phenytoin) were not removed at any tested concentrations. Two PPCPs (naproxen and triclosan) exhibited removals independent of PPCP concentration. PPCP removal efficiencies were dependent on initial concentrations for biphenylol, p-chloro-m-cresol, chlorophene, diclofenac, 5-fluorouracil, ibuprofen, and valproic acid, showing that PPCP concentration can affect biotransformation. Biofilms from sand samples collected from the 0.25- and 10-μg liter(-1) PPCP columns were pyrosequenced along with SAT soil samples collected on three consecutive days of a wetting and drying cycle to enable comparison of these two communities exposed to PPCPs. SAT communities were similar to column communities in taxonomy and phylotype composition, and both were found to contain close relatives of known PPCP degraders. The efficiency of biological removal of PPCPs was found to be dependent on the concentration at which the contamination occurs for some, but not all, PPCPs.

  • Three-dimensional stratification of bacterial biofilm populations in a moving bed biofilm reactor for nitritation anammox.

    Almstrand R, Persson F, Daims H, Ekenberg M, Christensson M, Wilén BM, Sörensson F, Hermansson M
    2014 - Int J Mol Sci, 15: 2191-2206

    Abstract: 

    Moving bed biofilm reactors (MBBRs) are increasingly used for nitrogen removal with nitritation-anaerobic ammonium oxidation (anammox) processes in wastewater treatment. Carriers provide protected surfaces where ammonia oxidizing bacteria (AOB) and anammox bacteria form complex biofilms. However, the knowledge about the organization of microbial communities in MBBR biofilms is sparse. We used new cryosectioning and imaging methods for fluorescence in situ hybridization (FISH) to study the structure of biofilms retrieved from carriers in anitritation-anammox MBBR. The dimensions of the carrier compartments and the biofilm cryosections after FISH showed good correlation, indicating little disturbance of biofilm samples by the treatment. FISH showed that Nitrosomonas europaea/eutropha-related cells dominated the AOB and Candidatus Brocadia fulgida-related cells dominated the anammox guild. New carriers were initially colonized by AOB, followed by anammox bacteria proliferating in the deeper biofilm layers, probably in anaerobic microhabitats created by AOB activity. Mature biofilms showed a pronounced three-dimensional stratification where AOB dominated closer to the biofilm-water interface, whereas anammox were dominant deeper into the carrier space and towards the walls. Our results suggest that current mathematical models may be oversimplifying these three-dimensional systems and unless the multidimensionality of these systems is considered, models may result in suboptimal design of MBBR carriers.

  • Longitudinal study of murine microbiota activity and interactions with the host during acute inflammation and recovery

    Schwab C, Berry D, Rauch I, Rennisch I, Ramesmayer J, Hainzl E, Heider S, Decker T, Kenner L, Müller M, Strobl B, Wagner M, Schleper C, Loy A, Urich T
    2014 - ISME J., 8(5):1101-14

    Abstract: 

    Although alterations in gut microbiota composition during acute colitis have been repeatedly observed, associated functional changes and therecovery from dysbiosis received little attention. In this study, we investigated structure and function of the gut microbiota during acute inflammationand recovery in a dextran sodium sulfate (DSS)-colitis mouse model using metatranscriptomics, bacterial 16S rRNA gene amplicon sequencing and monitoring of selected host markers. Parallel to an increase of host markers of inflammation during acute colitis, we observed relative abundance shifts and alterations in phylotype composition of the dominant bacterial orders Clostridiales and Bacteroidales, and an increase of the low abundant Enterobacteriales, Deferribacterales, Verrucomicrobiales and Erysipelotrichales. During recovery, the microbiota began to resume, but did not reach its original composition until the end of the experiment. Microbial gene expression was more resilient to disturbance, with pre-perturbation-type transcript profiles appearing quickly after acute colitis. The decrease of Clostridiales during inflammation correlated with a reduction of transcripts related to butyrate formation, suggesting a disturbance in host-microbe signalling and mucosal nutrient provision. The impact of acute inflammationon the Clostridiales was also characterized by a significant downregulation of their flagellin-encoding genes. In contrast, the abundance of members of the Bacteroidales increased along with an increase in transcripts related to mucin degradation. We propose that acute inflammation triggered a selective reaction of the immune system against flagella of commensals and temporarily altered murine microbiota composition and functions relevant for the host. Despite changes in specific interactions, the host-microbiota homeostasis revealed a remarkable ability for recovery.

  • Intestinal microbiota reduces genotoxic endpoints induced by high-energy protons.

    Maier I, Berry D, Schiesl R
    2014 - Radiat Res, 181: 45-53

    Abstract: 

    Ionizing space radiation causes oxidative DNA damage and triggers oxidative stress responses, and compromised DNA repair mechanisms can lead to increased risk of carcinogenesis. Young adult mice with developed innate and adaptive immune systems that harbored either a conventionalintestinal microbiota (CM) or an intestinal microbiota with a restricted microbial composition (RM) were irradiated with a total dose of 1 Gy delivered by high-energy protons (2.5 GeV/n, LET = 0.2-2 keV/μm) or silicon or iron ions (850 MeV/n, LET ≈ 50 keV/μm and 1 GeV/n, LET = 150 keV/μm, respectively). Six hours after whole-body irradiation, acute chromosomal DNA lesions were observed for RM mice but not CM mice. High-throughput rRNA gene sequencing of intestinal mucosal bacteria showed that Barnesiella intestinihominis and unclassified Bacterodiales were significantly more abundant in male RM mice than CM mice, and phylotype densities changed in irradiated mice. In addition, Helicobacter hepaticus and Bacteroides stercoris were higher in CM than RM mice. Elevated levels of persistently phosphorylated γ-H2AX were observed in RM mice exposed to high-energy protons compared to nonirradiated RM mice, and they also were associated with a decrease of the antioxidant glutathione in peripheral blood measured at four weeks after irradiation. After radiation exposure, CM mice showed lower levels of γ-H2AX phosphorylation than RM mice and an increase in specific RM-associated phylotypes, indicating a down-regulating force on DNA repair by differentially abundant phylotypes in RM versus a radiation-sensitive complex CM.

  • Manipulating conserved heme cavity residues of chlorite dismutase: effect on structure, redox chemistry, and reactivity.

    Hofbauer S, Gysel, K, Bellei M, Hagmueller A, Schaffner I, Mlynek G, Kostan J, Pirker K, Daims H, Furtmüller P, Battistuzzi G, Djinovic-Carugo K, Obinger C
    2014 - Biochemistry, 53: 77-89

    Abstract: 

    Chlorite dismutases (Clds) are heme b containing oxidoreductases that convert chlorite to chloride and molecular oxygen. In order to elucidate the role of conserved heme cavity residues in the catalysis of this reaction comprehensive mutational and biochemical analyses of Cld from "Candidatus Nitrospira defluvii" (NdCld) were performed. Particularly, point mutations of the cavity-forming residues R173, K141, W145, W146, and E210 were performed. The effect of manipulation in 12 single and double mutants was probed by UV-vis spectroscopy, spectroelectrochemistry, pre-steady-state and steady-state kinetics, and X-ray crystallography. Resulting biochemical data are discussed with respect to the known crystal structure of wild-type NdCld and the variants R173A and R173K as well as the structures of R173E, W145V, W145F, and the R173Q/W146Y solved in this work. The findings allow a critical analysis of the role of these heme cavity residues in the reaction mechanism of chlorite degradation that is proposed to involve hypohalous acid as transient intermediate and formation of an O═O bond. The distal R173 is shown to be important (but not fully essential) for the reaction with chlorite, and, upon addition of cyanide, it acts as a proton acceptor in the formation of the resulting low-spin complex. The proximal H-bonding network including K141-E210-H160 keeps the enzyme in its ferric (E°' = -113 mV) and mainly five-coordinated high-spin state and is very susceptible to perturbation.

  • Endospores of thermophilic bacteria as tracers of microbial dispersal by ocean currents

    Müller A, de Rezende JR, Hubert C, Kjeldsen KU, Lagkouvardos I, Berry D, Jørgensen BB, Loy A
    2014 - ISME J., 8: 1153-65

    Abstract: 

    Microbial biogeography is influenced by the combined effects of passive dispersal and environmental selection, but the contribution of either factor can be difficult to discern. As thermophilic bacteria cannot grow in the cold seabed, their inactive spores are not subject to environmental selection. We therefore conducted a global experimental survey using thermophilic endospores that are passively deposited by sedimentation to the cold seafloor as tracers to study the effect of dispersal by ocean currents on the biogeography of marine microorganisms. Our analysis of 81 different marine sediments from around the world identified 146 species-level 16S rRNA phylotypes of endospore-forming, thermophilic Firmicutes. Phylotypes showed various patterns of spatial distribution in the world oceans and were dispersal-limited to different degrees. Co-occurrence of several phylotypes in locations separated by great distances (west of Svalbard, the Baltic Sea and the Gulf of California) demonstrated a widespread but not ubiquitous distribution. In contrast, Arctic regions with water masses that are relatively isolated from global ocean circulation (Baffin Bay and east of Svalbard) were characterized by low phylotype richness and different compositions of phylotypes. The observed distribution pattern ofthermophilic endospores in marine sediments suggests that the impact of passive dispersal on marine microbial biogeography is controlled by the connectivity of local water masses to ocean circulation.

  • Polycyclic aromatic hydrocarbon degradation of a phytoplankton-associated Arenibacter spp. and description of Arenibacter algicola sp. nov., an aromatic hydrocarbon-degrading bacterium

    Gutierrez T, Rhodes G, Mishamandani S, Berry D, Whitman WB, Nichols PD, Semple KT, Aitken MD
    2014 - Appl Environ Microbiol., 80: 618-28

    Abstract: 

    Pyrosequencing of the bacterial community associated with a cosmopolitan marine diatom during enrichment with crude oil revealed severalArenibacter phylotypes, of which one (OTU-202) had become significantly enriched by the oil. Since members of the genus Arenibacter have not been previously shown to degrade hydrocarbons, we attempted to isolate a representative strain of this genus in order to directly investigate itshydrocarbon-degrading potential. Based on 16S rRNA sequencing, one isolate (designated strain TG409(T)) exhibited >99% sequence identity to three type strains of this genus. On the basis of phenotypic and genotypic characteristics, strain TG409(T) represents a novel species in the genusArenibacter, for which the name Arenibacter algicola sp. nov. is proposed. We reveal for the first time that polycyclic aromatic hydrocarbon (PAH)degradation is a shared phenotype among members of this genus, indicating that it could be used as a taxonomic marker for this genus. Kinetic data for PAH mineralization rates showed that naphthalene was preferred to phenanthrene, and its mineralization was significantly enhanced in the presence of glass wool (a surrogate for diatom cell surfaces). During enrichment on hydrocarbons, strain TG409(T) emulsified n-tetradecane and crude oil, and cells were found to be preferentially attached to oil droplets, indicating an ability by the strain to express cell surface amphiphilic substances (biosurfactants or bioemulsifiers) as a possible strategy to increase the bioavailability of hydrocarbons. This work adds to our growing knowledge on the diversity of bacterial genera in the ocean contributing to the degradation of oil contaminants and of hydrocarbon-degrading bacteria found living in association with marine eukaryotic phytoplankton.

  • NxrB encoding the beta subunit of nitrite oxidoreductase as functional and phylogenetic marker for nitrite-oxidizing Nitrospira

    Pester M, Maixner F, Berry D, Rattei T, Koch H, Lücker S, Nowka B, Richter A, Spieck E, Lebedeva E, Loy A, Wagner M, Daims H
    2014 - Environ Microbiol, 16: 3055-3071

    Abstract: 

    Nitrospira are the most widespread and diverse known nitrite-oxidizing bacteria and key nitrifiers in natural and engineered ecosystems. Nevertheless, their ecophysiology and environmental distribution are understudied due to the recalcitrance of Nitrospira to cultivation and the lack of a molecular functional marker, which would allow the detection of Nitrospira in the environment. Here we introduce nxrB, the gene encoding subunit beta of nitrite oxidoreductase, as a functional and phylogenetic marker for Nitrospira. Phylogenetic trees based on nxrB of Nitrospira were largely congruent to 16S rRNA-based phylogenies. By using new nxrB-selective PCR primers, we obtained almost full-length nxrB sequences from Nitrospira cultures, two activated sludge samples, and several geographically and climatically distinct soils. Amplicon pyrosequencing of nxrB fragments from 16 soils revealed a previously unrecognized diversity of terrestrial Nitrospira with 1,801 detected species-level OTUs (using an inferred species threshold of 95% nxrB identity). Richness estimates ranged from 10 to 946 co-existing Nitrospira species per soil. Comparison to an archaeal amoA dataset obtained from the same soils [Environ. Microbiol. 14: 525-539 (2012)] uncovered that ammonia-oxidizing archaea and Nitrospira communities were highly correlated across the soil samples, possibly indicating shared habitat preferences or specific biological interactions among members of these nitrifier groups.

Book chapters and other publications

5 Publications found
  • Investigation of microorganisms at the single-cell level using Raman Microspectroscopy and Nanometer-scale Secondary Ion Mass Spectrometry.

    2014 - pp. 203-211. in Molecular Methods and Applications in Microbiology. (Skovhus TL, Caffrey S, Hubert CRJ). Caister Academic Press, Norfolk, UK

    Abstract: 

    The field of single-cell ecophysiology has taken an exciting turn with the introduction of two powerful techniques, nanometer-scale secondary ion mass spectrometry (NanoSIMS) and Raman microspectroscopy. These techniques allow the investigation of microorganisms and their associated activity at the single-cell level. When combined with stable isotope tracers and/or identification of the targeted cell using fluorescence in situ hybridization (FISH), they have the potential to link the identity of a microorganism with its in situ activity. Raman microspectroscopy detects the scattering of light due to interaction with chemical bonds of cell constituents thereby providing compound specific information, which can also be used for bacterial identification. NanoSIMS permits highly sensitive analysis of multiple elements or isotopes with sub-micrometer spatial resolution, allowing the measurements of microbial activity when used in stable-isotope tracer experiments. In this chapter we present the principle for each technique, discuss their strengths and weaknesses, and document their applicability with particular emphasis on microbial ecology research. The integration of these single-cell techniques in the field of microbial ecology will improve our understanding of the ecophysiology of (novel) microorganisms across a multitude of environments.

  • Family Desulfomicrobiaceae

    Kuever J
    2014 - pp 97-102. in The Prokaryotes. (Rosenberg E, Stackebrandt E, DeLong EF, Lory S, Thompson F). Springer, New York

    Abstract: 

    Desulfomicrobiaceae, a family within the order Desulfovibrionales, embraces a single genusDesulfomicrobium. Besides their 16S rRNA gene sequence phylogeny, all members of the family are defined by a wide range of morphological and chemotaxonomic properties for the delineation of genera and species. Strictly anaerobic, having a respiratory type or fermentative type of metabolism. Members are either mesophilic or moderately thermophilic sulfate-reducing bacteria. Members of the family are found in various, predominantly marine habitats. All described species are chemoorganoheterotroph and chemolithoheterotroph with the exception of Desulfomicrobium macestii and Desulfomicrobium thermophilum which are described to be chemolithoautotroph. All members oxidize organic substrates incompletely to acetate with sulfate as electron acceptor, except some substrates which are exclusively fermented.

  • The family Nitrospinaceae

    Lücker S, Daims H
    2014 - 231-237. in The Prokaryotes. (Rosenberg E, Stackebrandt E, DeLong EF, Lory S, Thompson F). Springer, New York
  • The family Nitrospiraceae

    2014 - 733-749. in The Prokaryotes. (Rosenberg E, Stackebrandt E, DeLong EF, Lory S, Thompson F). Springer, New York

    Abstract: 

    Nitrospiraceae is the only established family in the phylum Nitrospirae and comprises the generaNitrospiraLeptospirillum, and Thermodesulfovibrio. In phylogenetic trees based on 16S rRNA gene sequences Nitrospira and Leptospirillum consistently cluster together, whereas Thermodesulfovibrioforms a separate branch within the phylum. The family is physiologically highly diverse and contains chemolithoautotrophic aerobic nitrite-oxidizing bacteria (Nitrospira), chemolithoautotrophic aerobic and acidophilic ferrous iron oxidizers (Leptospirillum), and anaerobic, thermophilic, chemoorganoheterotrophic or hydrogenotrophic sulfate reducers (Thermodesulfovibrio). Members of the family occur in a wide range of natural and man-made ecosystems. In particular, the genusNitrospira is almost ubiquitously distributed in oxic habitats and represents the predominant known nitrite oxidizers in nature, which catalyze the second step of nitrification and thus are essential for biogeochemical nitrogen cycling. All three genera are relevant for biotechnological processes. The genus Nitrospira contains the key nitrite oxidizers in biological wastewater treatment plants, whereas members of Leptospirillum are important iron oxidizers in the bioleaching of metal ores and are involved in acid mine drainage. Thermodesulfovibrio representatives occur in anaerobic digesters, where they contribute to the degradation of organic compounds and indirectly to the production of methane. Especially the members of Nitrospira and Leptospirillum are difficult to cultivate and most of their diversity has been detected by cultivation-independent molecular approaches.

  • Starting up microbial enhanced oil recovery (MEOR)

    Siegert M, Sitte J, Galushko A, Krüger M
    2014 - 142:1-94. in Geobiotechnology Springer Series: Advances Biochemical Engineering/Biotechnology. (Scheper T, Schippers A, Glombitza F, Sand W). Springer, New York

    Abstract: 

    This chapter gives the reader a practical introduction into microbial enhanced oil recovery (MEOR) including the microbial production of natural gas from oil. Decision makers who consider the use of one of these technologies are provided with the required scientific background as well as with practical advice for upgrading an existing laboratory in order to conduct microbiological experiments. We believe that the conversion of residual oilinto natural gas (methane) and the in situ production of biosurfactants are the most promising approaches for MEOR and therefore focus on these topics. Moreover, we give an introduction to the microbiology of oilfields and demonstrate that in situ microorganisms as well as injected cultures can help displace unrecoverable oil in place (OIP). After an initial research phase, the enhanced oil recovery (EOR) manager must decide whether MEORwould be economical. MEOR generally improves oil production but the increment may not justify the investment. Therefore, we provide a brief economical assessment at the end of this chapter. We describe the necessary state-of-the-art scientific equipment to guide EOR managers towards an appropriate MEOR strategy. Because it is inevitable to characterize the microbial community of an oilfield that should be treated using MEORtechniques, we describe three complementary start-up approaches. These are: (i) culturing methods, (ii) the characterization of microbialcommunities and possible bio-geochemical pathways by using molecular biology methods, and (iii) interfacial tension measurements. In conclusion, we hope that this chapter will facilitate a decision on whether to launch MEOR activities. We also provide an update on relevant literature for experienced MEOR researchers and oilfield operators. Microbiologists will learn about basic principles of interface physics needed to study the impact of microorganisms living on oil droplets. Last but not least, students and technicians trying to understand processes in oilfields and the techniques to examine them will, we hope, find a valuable source of information in this review.