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  • 1
    Online Resource
    Online Resource
    Metabolism of Reduced Methylated Sulfur Compounds in Anaerobic Sediments and by a Pure Culture of an Estuarine Methanogen
    American Society for Microbiology ; 1986
    In:  Applied and Environmental Microbiology Vol. 52, No. 5 ( 1986-11), p. 1037-1045
    Details
    In: Applied and Environmental Microbiology, American Society for Microbiology, Vol. 52, No. 5 ( 1986-11), p. 1037-1045
    Abstract: Addition of dimethylsulfide (DMS), dimethyldisulfide (DMDS), or methane thiol (MSH) to a diversity of anoxic aquatic sediments (e.g., fresh water, estuarine, alkaline/hypersaline) stimulated methane production. The yield of methane recovered from DMS was often 52 to 63%, although high concentrations of DMS (as well as MSH and DMDS) inhibited methanogenesis in some types of sediments. Production of methane from these reduced methylated sulfur compounds was blocked by 2-bromoethanesulfonic acid. Sulfate did not influence the metabolism of millimolar levels of DMS, DMDS, or MSH added to sediments. However, when DMS was added at ∼2-μM levels as [ 14 C]DMS, metabolism by sediments resulted in a 14 CH 4 / 14 CO 2 ratio of only 0.06. Addition of molybdate increased the ratio to 1.8, while 2-bromoethanesulfonic acid decreased it to 0, but did not block 14 CO 2 production. These results indicate the methanogens and sulfate reducers compete for DMS when it is present at low concentrations; however, at high concentrations, DMS is a “noncompetitive” substrate for methanogens. Metabolism of DMS by sediments resulted in the appearance of MSH as a transient intermediate. A pure culture of an obligately methylotrophic estuarine methanogen was isolated which was capable of growth on DMS. Metabolism of DMS by the culture also resulted in the transient appearance of MSH, but the organism could grow on neither MSH nor DMDS. The culture metabolized [ 14 C]-DMS to yield a 14 CH 4 / 14 CO 2 ratio of ∼2.8. Reduced methylated sulfur compounds represent a new class of substrates for methanogens and may be potential precursors of methane in a variety of aquatic habitats.
    Type of Medium: Online Resource
    ISSN: 0099-2240 , 1098-5336
    URL: Article
    DOI: 10.1128/aem.52.5.1037-1045.1986
    RVK:
    WA 15000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 1986
    detail.hit.zdb_id: 223011-2
    detail.hit.zdb_id: 1478346-0
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    Direct Determination of Nitrification in Marine Waters by Using the Short-Lived Radioisotope of Nitrogen, 13 N
    American Society for Microbiology ; 1990
    In:  Applied and Environmental Microbiology Vol. 56, No. 4 ( 1990-04), p. 1182-1184
    Details
    In: Applied and Environmental Microbiology, American Society for Microbiology, Vol. 56, No. 4 ( 1990-04), p. 1182-1184
    Abstract: Biological oxidation of radiolabeled 13 NH 4 + (half-life = 10 min) was observed within minutes in assays of an estuarine ammonium oxidizer and in natural populations of nitrifiers in coastal waters. Our estimates of turnover of the ammonium pool and rates of nitrification based on experiments using 13 N are consistent with previous values in the literature based on longer-term 15 N tracer experiments or on indirect methods and thus provide corroboration for the estimates by other researchers.
    Type of Medium: Online Resource
    ISSN: 0099-2240 , 1098-5336
    URL: Article
    DOI: 10.1128/aem.56.4.1182-1184.1990
    RVK:
    WA 15000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 1990
    detail.hit.zdb_id: 223011-2
    detail.hit.zdb_id: 1478346-0
    SSG: 12
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  • 3
    Online Resource
    Online Resource
    Amino Acid Cycling in Colonies of the Planktonic Marine Cyanobacterium Trichodesmium thiebautii
    American Society for Microbiology ; 1994
    In:  Applied and Environmental Microbiology Vol. 60, No. 11 ( 1994-11), p. 3989-3995
    Details
    In: Applied and Environmental Microbiology, American Society for Microbiology, Vol. 60, No. 11 ( 1994-11), p. 3989-3995
    Abstract: We examined diel trends in internal pools and net efflux of free amino acids in colonies of the nonheterocystous, diazotrophic cyanobacterium Trichodesmium thiebautii , freshly collected from waters of the Caribbean and the Bahamas. The kinetics of glutamate uptake by whole colonies were also examined. While intracolonial pools of most free amino acids were relatively constant through the day, pools of glutamate and glutamine varied over the diel cycle, with maxima during the early afternoon. This paralleled the daily cycle of nitrogenase activity. We also observed a large net release of these two amino acids from intact colonies. Glutamate release was typically 100 pmol of N colony -1 h -1 . This is about one-fourth the concurrent rate of N 2 fixation during the day. However, while nitrogenase activity only occurs during the day, net release of glutamate and glutamine persisted into the night and may therefore account for a greater loss of recently fixed N on a daily basis. This release may be an important route of new N input into tropical, oligotrophic waters. Whole colonies also displayed saturation kinetics with respect to glutamate uptake. The K s for whole colonies varied from 1.6 to 3.2 μM, or about 100-fold greater than typical ambient concentrations. Thus, uptake systems appear to be adapted to the higher concentrations of glutamate found within the intracellular spaces of the colonies. This suggests that glutamate may be a vehicle for N exchange among trichomes in the colony.
    Type of Medium: Online Resource
    ISSN: 0099-2240 , 1098-5336
    URL: Article
    DOI: 10.1128/aem.60.11.3989-3995.1994
    RVK:
    WA 15000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 1994
    detail.hit.zdb_id: 223011-2
    detail.hit.zdb_id: 1478346-0
    SSG: 12
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  • 4
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    Online Resource
    “ Candidatus Ethanoperedens,” a Thermophilic Genus of Archaea Mediating the Anaerobic Oxidation of Ethane
    American Society for Microbiology ; 2020
    In:  mBio Vol. 11, No. 2 ( 2020-04-28)
    Details
    In: mBio, American Society for Microbiology, Vol. 11, No. 2 ( 2020-04-28)
    Abstract: Cold seeps and hydrothermal vents deliver large amounts of methane and other gaseous alkanes into marine surface sediments. Consortia of archaea and partner bacteria thrive on the oxidation of these alkanes and its coupling to sulfate reduction. The inherently slow growth of the involved organisms and the lack of pure cultures have impeded the understanding of the molecular mechanisms of archaeal alkane degradation. Here, using hydrothermal sediments of the Guaymas Basin (Gulf of California) and ethane as the substrate, we cultured microbial consortia of a novel anaerobic ethane oxidizer, “ Candidatus Ethanoperedens thermophilum” (GoM-Arc1 clade), and its partner bacterium “ Candidatus Desulfofervidus auxilii,” previously known from methane-oxidizing consortia. The sulfate reduction activity of the culture doubled within one week, indicating a much faster growth than in any other alkane-oxidizing archaea described before. The dominance of a single archaeal phylotype in this culture allowed retrieval of a closed genome of “ Ca. Ethanoperedens,” a sister genus of the recently reported ethane oxidizer “ Candidatus Argoarchaeum.” The metagenome-assembled genome of “ Ca. Ethanoperedens” encoded a complete methanogenesis pathway including a methyl-coenzyme M reductase (MCR) that is highly divergent from those of methanogens and methanotrophs. Combined substrate and metabolite analysis showed ethane as the sole growth substrate and production of ethyl-coenzyme M as the activation product. Stable isotope probing demonstrated that the enzymatic mechanism of ethane oxidation in “ Ca. Ethanoperedens” is fully reversible; thus, its enzymatic machinery has potential for the biotechnological development of microbial ethane production from carbon dioxide. IMPORTANCE In the seabed, gaseous alkanes are oxidized by syntrophic microbial consortia that thereby reduce fluxes of these compounds into the water column. Because of the immense quantities of seabed alkane fluxes, these consortia are key catalysts of the global carbon cycle. Due to their obligate syntrophic lifestyle, the physiology of alkane-degrading archaea remains poorly understood. We have now cultivated a thermophilic, relatively fast-growing ethane oxidizer in partnership with a sulfate-reducing bacterium known to aid in methane oxidation and have retrieved the first complete genome of a short-chain alkane-degrading archaeon. This will greatly enhance the understanding of nonmethane alkane activation by noncanonical methyl-coenzyme M reductase enzymes and provide insights into additional metabolic steps and the mechanisms underlying syntrophic partnerships. Ultimately, this knowledge could lead to the biotechnological development of alkanogenic microorganisms to support the carbon neutrality of industrial processes.
    Type of Medium: Online Resource
    ISSN: 2161-2129 , 2150-7511
    URL: Article
    DOI: 10.1128/mBio.00600-20
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2020
    detail.hit.zdb_id: 2557172-2
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  • 5
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    Online Resource
    The Transcriptional Cycle Is Suited to Daytime N 2 Fixation in the Unicellular Cyanobacterium “ Candidatus Atelocyanobacterium thalassa” (UCYN-A)
    American Society for Microbiology ; 2019
    In:  mBio Vol. 10, No. 1 ( 2019-02-26)
    Details
    In: mBio, American Society for Microbiology, Vol. 10, No. 1 ( 2019-02-26)
    Abstract: Symbiosis between a marine alga and a N 2 -fixing cyanobacterium ( Cyanobacterium UCYN-A) is geographically widespread in the oceans and is important in the marine N cycle. UCYN-A is uncultivated and is an unusual unicellular cyanobacterium because it lacks many metabolic functions, including oxygenic photosynthesis and carbon fixation, which are typical in cyanobacteria. It is now presumed to be an obligate symbiont of haptophytes closely related to Braarudosphaera bigelowii . N 2 -fixing cyanobacteria use different strategies to avoid inhibition of N 2 fixation by the oxygen evolved in photosynthesis. Most unicellular cyanobacteria temporally separate the two incompatible activities by fixing N 2 only at night, but, surprisingly, UCYN-A appears to fix N 2 during the day. The goal of this study was to determine how the unicellular UCYN-A strain coordinates N 2 fixation and general metabolism compared to other marine cyanobacteria. We found that UCYN-A has distinct daily cycles of many genes despite the fact that it lacks two of the three circadian clock genes found in most cyanobacteria. We also found that the transcription patterns in UCYN-A are more similar to those in marine cyanobacteria that are capable of aerobic N 2 fixation in the light, such as Trichodesmium and heterocyst-forming cyanobacteria, than to those in Crocosphaera or Cyanothece species, which are more closely related to unicellular marine cyanobacteria evolutionarily. Our findings suggest that the symbiotic interaction has resulted in a shift of transcriptional regulation to coordinate UCYN-A metabolism with that of the phototrophic eukaryotic host, thus allowing efficient coupling of N 2 fixation (by the cyanobacterium) to the energy obtained from photosynthesis (by the eukaryotic unicellular alga) in the light. IMPORTANCE The symbiotic N 2 -fixing cyanobacterium UCYN-A, which is closely related to Braarudosphaera bigelowii , and its eukaryotic algal host have been shown to be globally distributed and important in open-ocean N 2 fixation. These unique cyanobacteria have reduced metabolic capabilities, even lacking genes for oxygenic photosynthesis and carbon fixation. Cyanobacteria generally use energy from photosynthesis for nitrogen fixation but require mechanisms for avoiding inactivation of the oxygen-sensitive nitrogenase enzyme by ambient oxygen (O 2 ) or the O 2 evolved through photosynthesis. This study showed that symbiosis between the N 2 -fixing cyanobacterium UCYN-A and its eukaryotic algal host has led to adaptation of its daily gene expression pattern in order to enable daytime aerobic N 2 fixation, which is likely more energetically efficient than fixing N 2 at night, as found in other unicellular marine cyanobacteria.
    Type of Medium: Online Resource
    ISSN: 2161-2129 , 2150-7511
    URL: Article
    DOI: 10.1128/mBio.02495-18
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2019
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  • 6
    Online Resource
    Online Resource
    Activity and Metabolic Versatility of Complete Ammonia Oxidizers in Full-Scale Wastewater Treatment Systems
    American Society for Microbiology ; 2020
    In:  mBio Vol. 11, No. 2 ( 2020-04-28)
    Details
    In: mBio, American Society for Microbiology, Vol. 11, No. 2 ( 2020-04-28)
    Abstract: The recent discovery of complete ammonia oxidizers (comammox) contradicts the paradigm that chemolithoautotrophic nitrification is always catalyzed by two different microorganisms. However, our knowledge of the survival strategies of comammox in complex ecosystems, such as full-scale wastewater treatment plants (WWTPs), remains limited. Analyses of genomes and in situ transcriptomes of four comammox organisms from two full-scale WWTPs revealed that comammox were active and showed a surprisingly high metabolic versatility. A gene cluster for the utilization of urea and a gene encoding cyanase suggest that comammox may use diverse organic nitrogen compounds in addition to free ammonia as the substrates. The comammox organisms also encoded the genomic potential for multiple alternative energy metabolisms, including respiration with hydrogen, formate, and sulfite as electron donors. Pathways for the biosynthesis and degradation of polyphosphate, glycogen, and polyhydroxyalkanoates as intracellular storage compounds likely help comammox survive unfavorable conditions and facilitate switches between lifestyles in fluctuating environments. One of the comammox strains acquired from the anaerobic tank encoded and transcribed genes involved in homoacetate fermentation or in the utilization of exogenous acetate, both pathways being unexpected in a nitrifying bacterium. Surprisingly, this strain also encoded a respiratory nitrate reductase which has not yet been found in any other Nitrospira genome and might confer a selective advantage to this strain over other Nitrospira strains in anoxic conditions. IMPORTANCE The discovery of comammox in the genus Nitrospira changes our perception of nitrification. However, genomes of comammox organisms have not been acquired from full-scale WWTPs, and very little is known about their survival strategies and potential metabolisms in complex wastewater treatment systems. Here, four comammox metagenome-assembled genomes and metatranscriptomic data sets were retrieved from two full-scale WWTPs. Their impressive and—among nitrifiers—unsurpassed ecophysiological versatility could make comammox Nitrospira an interesting target for optimizing nitrification in current and future bioreactor configurations.
    Type of Medium: Online Resource
    ISSN: 2161-2129 , 2150-7511
    URL: Article
    DOI: 10.1128/mBio.03175-19
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2020
    detail.hit.zdb_id: 2557172-2
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  • 7
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    Online Resource
    Insights into Hydrocarbon Formation by Nitrogenase Cofactor Homologs
    American Society for Microbiology ; 2015
    In:  mBio Vol. 6, No. 2 ( 2015-05)
    Details
    In: mBio, American Society for Microbiology, Vol. 6, No. 2 ( 2015-05)
    Abstract: Nitrogenase is a metalloenzyme that is highly complex in structure and uniquely versatile in function. It catalyzes two reactions that parallel two important industrial processes: the reduction of nitrogen to ammonia, which parallels the Haber-Bosch process in ammonia production, and the reduction of carbon monoxide to hydrocarbons, which parallels the Fischer-Tropsch process in fuel production. Thus, the significance of nitrogenase can be appreciated from the perspective of the useful products it generates: (i) ammonia, the “fixed” nitrogen that is essential for the existence of the entire human population; and (ii) hydrocarbons, the “recycled” carbon fuel that could be used to directly address the worldwide energy shortage. This article provides initial insights into the catalytic characteristics of various nitrogenase cofactors in hydrocarbon formation. The reported assay system provides a useful tool for mechanistic investigations of this reaction while suggesting the possibility of designing bioinspired catalysts based on nitrogenase cofactors.
    Type of Medium: Online Resource
    ISSN: 2161-2129 , 2150-7511
    URL: Article
    DOI: 10.1128/mBio.00307-15
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2015
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  • 8
    Online Resource
    Online Resource
    The Marine Nitrogen Cycle
    American Society for Microbiology ; 2008
    In:  Microbe Magazine Vol. 3, No. 4 ( 2008-04-01), p. 186-192
    Details
    In: Microbe Magazine, American Society for Microbiology, Vol. 3, No. 4 ( 2008-04-01), p. 186-192
    Type of Medium: Online Resource
    ISSN: 1558-7452 , 1558-7460
    URL: Article
    DOI: 10.1128/microbe.3.186.1
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2008
    detail.hit.zdb_id: 2232608-X
    SSG: 12
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  • 9
    Online Resource
    Online Resource
    Intercellular Diffusion of a Fluorescent Sucrose Analog via the Septal Junctions in a Filamentous Cyanobacterium
    American Society for Microbiology ; 2015
    In:  mBio Vol. 6, No. 2 ( 2015-05)
    Details
    In: mBio, American Society for Microbiology, Vol. 6, No. 2 ( 2015-05)
    Abstract: Anabaena and its relatives are filamentous cyanobacteria that exhibit a sophisticated form of prokaryotic multicellularity, with the formation of differentiated cell types, including normal photosynthetic cells and specialized nitrogen-fixing cells called heterocysts. The question of how heterocysts communicate and exchange metabolites with other cells in the filament is key to understanding this form of bacterial multicellularity. Here we provide the first information on the intercellular exchange of a physiologically important molecule, sucrose. We show that a fluorescent sucrose analog can be imported into the Anabaena cytoplasm by a sucrose import system. Once in the cytoplasm, it is rapidly and reversibly exchanged among all of the cells in the filament by diffusion across the septal junctions. Photosynthetically produced sucrose likely follows the same route from cytoplasm to cytoplasm. We identify some of the septal proteins involved in sucrose exchange, and our results indicate that these proteins form structures functionally analogous to metazoan gap junctions.
    Type of Medium: Online Resource
    ISSN: 2161-2129 , 2150-7511
    URL: Article
    DOI: 10.1128/mBio.02109-14
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2015
    detail.hit.zdb_id: 2557172-2
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  • 10
    Online Resource
    Online Resource
    Transposon and Deletion Mutagenesis of Genes Involved in Perchlorate Reduction in Azospira suillum PS
    American Society for Microbiology ; 2014
    In:  mBio Vol. 5, No. 1 ( 2014-02-28)
    Details
    In: mBio, American Society for Microbiology, Vol. 5, No. 1 ( 2014-02-28)
    Abstract: Although perchlorate is generated naturally in the environment, groundwater contamination is largely a result of industrial activity. Bacteria capable of respiring perchlorate and remediating contaminated water have been isolated, but relatively little is known about the biochemistry and genetics of this process. Here we used two complementary approaches to identify genes involved in perchlorate reduction. Most of these genes are located on a genomic island, which is potentially capable of moving between organisms. Some of the genes identified are known to be directly involved in the metabolism of perchlorate, but other new genes likely regulate the metabolism in response to environmental signals. This work has uncovered new questions about the regulation, energetics, and evolution of perchlorate reduction but also presents the tools to address them.
    Type of Medium: Online Resource
    ISSN: 2161-2129 , 2150-7511
    URL: Article
    DOI: 10.1128/mBio.00769-13
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2014
    detail.hit.zdb_id: 2557172-2
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