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Amelia-elena Rotaru - One of the best experts on this subject based on the ideXlab platform.

  • Baltic Sea methanogens compete with acetogens for electrons from metallic iron
    The ISME Journal, 2019
    Co-Authors: Paola Andrea Palacios, Carolin Regina Löscher, Bo Thamdrup, Oona Snoeyenbos-west, Amelia-elena Rotaru
    Abstract:

    Microbially induced corrosion of metallic iron (Fe0)-containing structures is an environmental and economic hazard. Methanogens are abundant in low-sulfide environments and yet their specific role in Fe0 corrosion is poorly understood. In this study, Sporomusa and Methanosarcina dominated enrichments from Baltic Sea methanogenic sediments that were established with Fe0 as the sole electron donor and CO2 as the electron acceptor. The Baltic-Sporomusa was phylogenetically affiliated to the electroactive acetogen S. silvacetica. Baltic-Sporomusa adjusted rapidly to growth on H2. On Fe0, spent filtrate enhanced growth of this acetogen suggesting that it was using endogenous enzymes to retrieve electrons and produce acetate. Previous studies have proposed that acetate produced by acetogens can feed commensal acetoclastic methanogens such as Methanosarcina. However, Baltic-methanogens could not generate methane from acetate, plus the decrease or absence of acetogens stimulated their growth. The decrease in numbers of Sporomusa was concurrent with an upsurge in Methanosarcina and increased methane production, suggesting that methanogens compete with acetogens for electrons from Fe0. Furthermore, Baltic-methanogens were unable to use H2 (1.5 atm) for methanogenesis and were inhibited by spent filtrate additions, indicating that enzymatically produced H2 is not a favorable electron donor. We hypothesize that Baltic-methanogens retrieve electrons from Fe0 via a yet enigmatic direct electron uptake mechanism.

  • Baltic Methanosarcina and Clostridium compete for electrons from metallic iron
    bioRxiv, 2019
    Co-Authors: Paola Andrea Palacios Jaramillo, Carolin Regina Löscher, Bo Thamdrup, Oona Snoeyenbos-west, Amelia-elena Rotaru
    Abstract:

    Abstract Microbial induced corrosion of steel structures, used for transport or storage of fuels, chemical weapons or waste radionuclides, is an environmental and economic threat. In non-sulfidic environments, the exact role of methanogens in steel corrosion is poorly understood. From the non-sulfidic, methanogenic sediments of the Baltic Sea corrosive communities were enriched using exclusively Fe0 as electron donor and CO2 as electron acceptor. Methane and acetate production were persistent for three years of successive transfers. Methanosarcina and Clostridium were attached to the Fe0, and dominated metagenome libraries. Since prior reports indicated Methanosarcina were merely commensals, consuming the acetate produced by acetogens, we investigated whether these methanogens were capable of Fe0 corrosion without bacterial partners (inhibited by an antibiotic cocktail). Unassisted, methanogens corroded Fe0 to Fe2+ at similar rates to the mixed community. Surprisingly, in the absence of competitive bacteria, Baltic-Methanosarcina produced six times more methane than they did in the mixed community. This signifies that Baltic-Methanosarcina achieved better corrosion alone, exclusive of an operative bacterial partner. Our results also show that together with acetogens, Methanosarcina interact competitively to retrieve electrons from Fe0 rather than as commensals as previously assumed.

  • extracellular electron uptake by two Methanosarcina species
    bioRxiv, 2018
    Co-Authors: Oona Snoeyenboswest, Bo Thamdrup, Lars Ditlev Morck Ottosen, Amelia-elena Rotaru
    Abstract:

    Direct electron uptake by prokaryotes is a recently described mechanism with a potential application for energy and CO2 storage into value added chemicals. Members of Methanosarcinales, an environmentally and biotechnologically relevant group of methanogens, were previously shown to retrieve electrons from an extracellular electrogenic partner performing Direct Interspecies Electron Transfer (DIET) and were therefore proposed to be electroactive. However, their intrinsic electroactivity has never been examined. In this study, we tested two methanogens belonging to Methanosarcina, M. barkeri and M. horonobensis, regarding their ability to accept electrons directly from insoluble electron donors like other cells, conductive particles and electrodes. Both methanogens were able to retrieve electrons from Geobacter metallireducens via DIET. Furthermore, DIET was also stimulated upon addition of electrically conductive granular activated carbon (GAC) when each was co-cultured with G. metallireducens. However, when provided with a cathode poised at - 400 mV (vs SHE), only M. barkeri could perform electromethanogenesis. In contrast, the strict hydrogenotrophic methanogen, Methanobacterium formicicum, did not produce methane regardless of the type of insoluble electron donor provided (Geobacter cells, GAC or electrodes). A comparison of functional gene categories between Methanobacterium and the two Methanosarcinas revealed a higher abundance of genes associated with extracellular electron transfer in Methanosarcina species. Between the two Methanosarcina we observed differences regarding energy metabolism, which could explain dissimilarities concerning electromethanogenesis at fixed potentials. We suggest that these dissimilarities are minimized in the presence of an electrogenic DIET partner (i.e. Geobacter), which can modulate its surface redox potentials by adjusting the expression of electroactive surface proteins.

  • conductive particles enable syntrophic acetate oxidation between geobacter and Methanosarcina from coastal sediments
    Mbio, 2018
    Co-Authors: Amelia-elena Rotaru, Oona Snoeyenboswest, Pravin Malla Shrestha, Hryhoriy Stryhanyuk, Federica Calabrese, Florin Musat, Hannah Sophia Weber, Per O J Hall, Hans H Richnow, Niculina Musat
    Abstract:

    : Coastal sediments are rich in conductive particles, possibly affecting microbial processes for which acetate is a central intermediate. In the methanogenic zone, acetate is consumed by methanogens and/or syntrophic acetate-oxidizing (SAO) consortia. SAO consortia live under extreme thermodynamic pressure, and their survival depends on successful partnership. Here, we demonstrate that conductive particles enable the partnership between SAO bacteria (i.e., Geobacter spp.) and methanogens (Methanosarcina spp.) from the coastal sediments of the Bothnian Bay of the Baltic Sea. Baltic methanogenic sediments were rich in conductive minerals, had an apparent isotopic fractionation characteristic of CO2-reductive methanogenesis, and were inhabited by Geobacter and Methanosarcina As long as conductive particles were delivered, Geobacter and Methanosarcina persisted, whereas exclusion of conductive particles led to the extinction of Geobacter Baltic Geobacter did not establish a direct electric contact with Methanosarcina, necessitating conductive particles as electrical conduits. Within SAO consortia, Geobacter was an efficient [13C]acetate utilizer, accounting for 82% of the assimilation and 27% of the breakdown of acetate. Geobacter benefits from the association with the methanogen, because in the absence of an electron acceptor it can use Methanosarcina as a terminal electron sink. Consequently, inhibition of methanogenesis constrained the SAO activity of Geobacter as well. A potential benefit for Methanosarcina partnering with Geobacter is that together they competitively exclude acetoclastic methanogens like Methanothrix from an environment rich in conductive particles. Conductive particle-mediated SAO could explain the abundance of acetate oxidizers like Geobacter in the methanogenic zone of sediments where no electron acceptors other than CO2 are available.IMPORTANCE Acetate-oxidizing bacteria are known to thrive in mutualistic consortia in which H2 or formate is shuttled to a methane-producing Archaea partner. Here, we discovered that such bacteria could instead transfer electrons via conductive minerals. Mineral SAO (syntrophic acetate oxidation) could be a vital pathway for CO2-reductive methanogenesis in the environment, especially in sediments rich in conductive minerals. Mineral-facilitated SAO is therefore of potential importance for both iron and methane cycles in sediments and soils. Additionally, our observations imply that agricultural runoff or amendments with conductive chars could trigger a significant increase in methane emissions.

  • potential for Methanosarcina to contribute to uranium reduction during acetate promoted groundwater bioremediation
    Microbial Ecology, 2018
    Co-Authors: Dawn E Holmes, Ludovic Giloteaux, Liying Wang, Pravin Malla Shrestha, Kenneth H Williams, Derek R Lovley, Roberto Orelana, Amelia-elena Rotaru
    Abstract:

    Previous studies of acetate-promoted bioremediation of uranium-contaminated aquifers focused on Geobacter because no other microorganisms that can couple the oxidation of acetate with U(VI) reduction had been detected in situ. Monitoring the levels of methyl CoM reductase subunit A (mcrA) transcripts during an acetate-injection field experiment demonstrated that acetoclastic methanogens from the genus Methanosarcina were enriched after 40 days of acetate amendment. The increased abundance of Methanosarcina corresponded with an accumulation of methane in the groundwater. In order to determine whether Methanosarcina species could be participating in U(VI) reduction in the subsurface, cell suspensions of Methanosarcina barkeri were incubated in the presence of U(VI) with acetate provided as the electron donor. U(VI) was reduced by metabolically active M. barkeri cells; however, no U(VI) reduction was observed in inactive controls. These results demonstrate that Methanosarcina species could play an important role in the long-term bioremediation of uranium-contaminated aquifers after depletion of Fe(III) oxides limits the growth of Geobacter species. The results also suggest that Methanosarcina have the potential to influence uranium geochemistry in a diversity of anaerobic sedimentary environments.

William W Metcalf - One of the best experts on this subject based on the ideXlab platform.

  • methylamine specific methyltransferase paralogs in Methanosarcina are functionally distinct despite frequent gene conversion
    The ISME Journal, 2019
    Co-Authors: Dipti D Nayak, William W Metcalf
    Abstract:

    Sequenced archaeal genomes are mostly smaller and more streamlined than typical bacterial genomes; however, members of the Methanosarcina genus within the Euryarchaeaota are a significant exception, with M. acetivorans being the largest archaeal genome (5.8 Mbp) sequenced thus far. This finding is partially explained by extensive gene duplication within Methanosarcina spp. Significantly, the evolutionary pressures leading to gene duplication and subsequent genome expansion have not been well investigated, especially with respect to biological methane production (methanogenesis), which is the key biological trait of these environmentally important organisms. In this study, we address this question by specifically probing the functional evolution of two methylamine-specific methyltransferase paralogs in members of the Methanosarcina genus. Using the genetically tractable strain, M. acetivorans, we first show that the two paralogs have distinct cellular functions: one being required for methanogenesis from methylamine, the other for use of methylamine as a nitrogen source. Subsequently, through comparative sequence analyses, we show that functional divergence of paralogs is primarily mediated by divergent evolution of the 5′ regulatory region, despite frequent gene conversion within the coding sequence. This unique evolutionary paradigm for functional divergence of genes post-duplication underscores a divergent role for an enzyme singularly associated with methanogenic metabolism in other aspects of cell physiology.

  • Genomic and phenotypic differentiation among Methanosarcina mazei populations from Columbia River sediment
    The ISME Journal, 2015
    Co-Authors: Nicholas D Youngblut, William W Metcalf, Joseph S Wirth, James R Henriksen, Maria Smith, Holly Simon, Rachel J Whitaker
    Abstract:

    Methanogenic archaea are genotypically and phenotypically diverse organisms that are integral to carbon cycling in anaerobic environments. Owing to their genetic tractability and ability to be readily cultivated, Methanosarcina spp. have become a powerful model system for understanding methanogen biology at the cellular systems level. However, relatively little is known of how genotypic and phenotypic variation is partitioned in Methanosarcina populations inhabiting natural environments and the possible ecological and evolutionary implications of such variation. Here, we have identified how genomic and phenotypic diversity is partitioned within and between Methanosarcina mazei populations obtained from two different sediment environments in the Columbia River Estuary (Oregon, USA). Population genomic analysis of 56 M. mazei isolates averaging

  • genomic and phenotypic differentiation among Methanosarcina mazei populations from columbia river sediment
    The ISME Journal, 2015
    Co-Authors: William W Metcalf, Nicholas D Youngblut, Joseph S Wirth, James R Henriksen, Maria W Smith, Holly M Simon, Rachel J Whitaker
    Abstract:

    Methanogenic archaea are genotypically and phenotypically diverse organisms that are integral to carbon cycling in anaerobic environments. Owing to their genetic tractability and ability to be readily cultivated, Methanosarcina spp. have become a powerful model system for understanding methanogen biology at the cellular systems level. However, relatively little is known of how genotypic and phenotypic variation is partitioned in Methanosarcina populations inhabiting natural environments and the possible ecological and evolutionary implications of such variation. Here, we have identified how genomic and phenotypic diversity is partitioned within and between Methanosarcina mazei populations obtained from two different sediment environments in the Columbia River Estuary (Oregon, USA). Population genomic analysis of 56 M. mazei isolates averaging <1% nucleotide divergence revealed two distinct clades, which we refer to as ‘mazei-T’ and ‘mazei-WC’. Genomic analyses showed that these clades differed in gene content and fixation of allelic variants, which point to potential differences in primary metabolism and also interactions with foreign genetic elements. This hypothesis of niche partitioning was supported by laboratory growth experiments that revealed significant differences in trimethylamine utilization. These findings improve our understanding of the ecologically relevant scales of genomic variation in natural systems and demonstrate interactions between genetic and ecological diversity in these easily cultivable and genetically tractable model methanogens.

  • genetic methods for Methanosarcina species
    Methods in Enzymology, 2011
    Co-Authors: Nicole R Buan, Gargi Kulkarni, William W Metcalf
    Abstract:

    Unlike most methanogenic microorganisms, Methanosarcina species are capable of utilizing a variety of growth substrates, a trait that greatly simplifies genetic analysis of the methanogenic process. The genetic tools and techniques discussed in this chapter form the basis for all genetic experiments in Methanosarcina acetivorans C2A and Methanosarcina barkeri Fusaro, two methanogens that are routinely used as model organisms for genetic experiments. Based on a number of reports, it is likely that they are portable to other Methanosarcina species, and perhaps to other methanogens as well. Here, we outline the procedures for high-efficiency transformation using liposomes, gene expression from a plasmid, and exploitation of homologous and site-specific recombination to add and delete genes from the chromosome. Finally, we outline the method for testing whether a gene is essential. These methods can be adapted and combined in any number of ways to design genetic experiments in Methanosarcina.

  • differences in hydrogenase gene expression between Methanosarcina acetivorans and Methanosarcina barkeri
    Journal of Bacteriology, 2009
    Co-Authors: Adam M Guss, Gargi Kulkarni, William W Metcalf
    Abstract:

    Methanosarcina acetivorans C2A encodes three putative hydrogenases, including one cofactor F420-linked (frh) and two methanophenazine-linked (vht) enzymes. Comparison of the amino acid sequences of these putative hydrogenases to those of Methanosarcina barkeri and Methanosarcina mazei shows that each predicted subunit contains all the known residues essential for hydrogenase function. The DNA sequences upstream of the genes in M. acetivorans were aligned with those in other Methanosarcina species to identify conserved transcription and translation signals. The M. acetivorans vht promoter region is well conserved among the sequenced Methanosarcina species, while the second vht-type homolog (here called vhx) and frh promoters have only limited similarity. To experimentally determine whether these promoters are functional in vivo, we constructed and characterized both M. acetivorans and M. barkeri strains carrying reporter gene fusions to each of the M. acetivorans and M. barkeri hydrogenase promoters. Generally, the M. acetivorans gene fusions are not expressed in either organism, suggesting that cis-acting mutations inactivated the M. acetivorans promoters. The M. barkeri hydrogenase gene fusions, on the other hand, are expressed in both organisms, indicating that M. acetivorans possesses the machinery to express hydrogenases, although it does not express its own hydrogenases. These data are consistent with specific inactivation of the M. acetivorans hydrogenase promoters and highlight the importance of testing hypotheses generated by using genomic data.

Birgitte Kiær Ahring - One of the best experts on this subject based on the ideXlab platform.

  • growth kinetics of thermophilic Methanosarcina spp isolated from full scale biogas plants treating animal manures
    FEMS Microbiology Ecology, 2000
    Co-Authors: Zuzana Mladenovska, Birgitte Kiær Ahring
    Abstract:

    This study determines the growth kinetics of thermophilic strains of Methanosarcina spp. from full-scale thermophilic biogas plants. The complete set of kinetic parameters, including maximum specific growth rate μmax, half saturation constant KS, acetate threshold concentration and cell growth yield YX/S, were determined for six Methanosarcina strains newly isolated from full-scale reactors and the type strain Methanosarcina thermophila TM-1T. The kinetic experiments were performed in media supplemented with acetate and activated carbon at the optimum growth temperatures of the individual strains, 50–55°C. The μmax values of the isolates were in the range of 0.044–0.064 h−1, the KS ranged from 6.5 to 24.7 mM acetate and the threshold for acetate utilization from 0.11 to 0.40 mM. The cell growth yields of the strains were between 0.78 and 2.97 g dry weight cells mol−1 acetate. The six isolates exhibited significantly higher μmax and had higher affinity to acetate than the type strain M. thermophila TM-1T. Generally, the affinities of thermophilic Methanosarcina strains tested in this study cover a similar range to those reported in the literature for mesophilic Methanosarcina spp. with acetate as substrate. The strains isolated from plants treating mixtures of animal manures and industrial organic wastes had higher affinity for acetate and lower thresholds than strains isolated from reactors operating solely on manures.

  • Mixotrophic growth of two thermophilic Methanosarcina strains, Methanosarcina thermophila TM-1 and Methanosarcina sp. SO-2P, on methanol and hydrogen/carbon dioxide
    Applied Microbiology and Biotechnology, 1997
    Co-Authors: Zuzana Mladenovska, Birgitte Kiær Ahring
    Abstract:

    Two thermophilic strains, Methanosarcina thermophila TM-1 and Methanosarcina sp. SO-2P, were capable of mixotrophic growth on methanol and H2/CO2. Activated carbon was, however, found to be necessary to support good growth. Both strains used hydrogen and methanol simultaneously. When methanol was depleted, hydrogen utilization continued and methane was further produced with concurrent cell growth. UV epifluorescence microscopy revealed that aggregates of both strains exhibited a bright red fluorescence besides the usual blue-green fluorescence.

Robert P. Gunsalus - One of the best experts on this subject based on the ideXlab platform.

  • mining proteomic data to expose protein modifications in Methanosarcina mazei strain go1
    Frontiers in Microbiology, 2015
    Co-Authors: Deborah R Leon, Jimmy A Ytterberg, Pinmanee Boontheung, Robert P. Gunsalus
    Abstract:

    Proteomic tools identify constituents of complex mixtures, often delivering long lists of identified proteins. The high-throughput methods excel at matching tandem mass spectrometry data to spectra predicted from sequence databases. Unassigned mass spectra are ignored, but could, in principle, provide valuable information on unanticipated modifications and improve protein annotations while consuming limited quantities of material. Strategies to “mine” information from these discards are presented, along with discussion of features that, when present, provide strong support for modifications. In this study we mined LC-MS/MS datasets of proteolytically-digested concanavalin A pull down fractions from Methanosarcina mazei Go1 cell lysates. Analyses identified 154 proteins. Many of the observed proteins displayed post-translationally modified forms, including O-formylated and methyl-esterified segments that appear biologically relevant (i.e., not artifacts of sample handling). Interesting cleavages and modifications (e.g., S-cyanylation and trimethylation) were observed near catalytic sites of methanogenesis enzymes. Of 31 Methanosarcina protein N-termini recovered by concanavalin A binding or from a previous study, only M. mazei S-layer protein MM1976 and its M. acetivorans C2A orthologue, MA0829, underwent signal peptide excision. Experimental results contrast with predictions from algorithms SignalP 3.0 and Exprot, which were found to over-predict the presence of signal peptides. Proteins MM0002, MM0716, MM1364, and MM1976 were found to be glycosylated, and employing chromatography tailored specifically for glycopeptides will likely reveal more. This study supplements limited, existing experimental datasets of mature archaeal N-termini, including presence or absence of signal peptides, translation initiation sites, and other processing. Methanosarcina surface and membrane proteins are richly modified.

  • identification of the major expressed s layer and cell surface layer related proteins in the model methanogenic archaea Methanosarcina barkeri fusaro and Methanosarcina acetivorans c2a
    Archaea, 2012
    Co-Authors: Lars Rohlin, Deborah R Leon, Robert P. Gunsalus
    Abstract:

    Many archaeal cell envelopes contain a protein coat or sheath composed of one or more surface exposed proteins. These surface layer (S-layer) proteins contribute structural integrity and protect the lipid membrane from environmental challenges. To explore the species diversity of these layers in the Methanosarcinaceae, the major S-layer protein in Methanosarcina barkeri strain Fusaro was identified using proteomics. The Mbar_A1758 gene product was present in multiple forms with apparent sizes of 130, 120, and 100 kDa, consistent with post-translational modifications including signal peptide excision and protein glycosylation. A protein with features related to the surface layer proteins found in Methanosarcina acetivorans C2A and Methanosarcina mazei Goel was identified in the M. barkeri genome. These data reveal a distinct conserved protein signature with features and implied cell surface architecture in the Methanosarcinaceae that is absent in other archaea. Paralogous gene expression patterns in two Methanosarcina species revealed abundant expression of a single S-layer paralog in each strain. Respective promoter elements were identified and shown to be conserved in mRNA coding and upstream untranslated regions. Prior M. acetivorans genome annotations assigned S-layer or surface layer associated roles of eighty genes: however, of 68 examined none was significantly expressed relative to the experimentally determined S-layer gene.

  • DNA microarray analysis of Methanosarcina mazei Gö1 reveals adaptation to different methanogenic substrates
    Molecular Genetics and Genomics, 2005
    Co-Authors: Raymond Hovey, Robert P. Gunsalus, Sabine Lentes, Armin Ehrenreich, Kirsty Salmon, Karla Saba, Gerhard Gottschalk, Uwe Deppenmeier
    Abstract:

    Methansarcina mazei Gö1 DNA arrays were constructed and used to evaluate the genomic expression patterns of cells grown on either of two alternative methanogenic substrates, acetate or methanol, as sole carbon and energy source. Analysis of differential transcription across the genome revealed two functionally grouped sets of genes that parallel the central biochemical pathways in, and reflect many known features of, acetate and methanol metabolism. These include the acetate-induced genes encoding acetate activating enzymes, acetyl-CoA synthase/CO dehydrogenase, and carbonic anhydrase. Interestingly, additional genes expressed at significantly higher levels during growth on acetate included two energy-conserving complexes (the Ech hydrogenase, and the A_1A_0-type ATP synthase). Many previously unknown features included the induction by acetate of genes coding for ferredoxins and flavoproteins, an aldehyde:ferredoxin oxidoreductase, enzymes for the synthesis of aromatic amino acids, and components of iron, cobalt and oligopeptide uptake systems. In contrast, methanol-grown cells exhibited elevated expression of genes assigned to the methylotrophic pathway of methanogenesis. Expression of genes for components of the translation apparatus was also elevated in cells grown in the methanol medium relative to acetate, and was correlated with the faster growth rate observed on the former substrate. These experiments provide the first comprehensive insight into substrate-dependent gene expression in a methanogenic archaeon. This genome-wide approach, coupled with the complementary molecular and biochemical tools, should greatly accelerate the exploration of Methanosarcina cell physiology, given the present modest level of our knowledge of these large archaeal genomes.

  • Disaggregation of Methanosarcina spp. and Growth as Single Cells at Elevated Osmolarity.
    Applied and Environmental Microbiology, 1993
    Co-Authors: Kevin R Sowers, Jane E. Boone, Robert P. Gunsalus
    Abstract:

    Abstract The effect of medium osmolarity on the morphology and growth of Methanosarcina barkeri, Methanosarcina thermophila, Methanosarcina mazei, Methanosarcina vacuolata, and Methanosarcina acetivorans was examined. Each strain was adapted for growth in NaCl concentrations ranging from 0.05 to 1.0 M. Methanosarcina spp. isolated from both marine and nonmarine sources exhibited similar growth characteristics at all NaCl concentrations tested, demonstrating that these species are capable of adapting to a similar range of medium osmolarities. Concomitant with the adaptation in 0.4 to 1.0 M NaCl, all strains disaggregated and grew as single cells rather than in the characteristic multicellular aggregates. Aggregated cells had a methanochondroitin outer layer, while disaggregated single cells lacked the outer layer but retained the protein S-layer adjacent to the cell membrane. Synthesis of glucuronic acid, a major component of methanochondroitin, was reduced 20-fold in the single-cell form of M. barkeri when compared with synthesis in aggregated cells. Strains with the methanochondroitin outer cell layer exhibited enhanced stability at low (

Zuzana Mladenovska - One of the best experts on this subject based on the ideXlab platform.

  • growth kinetics of thermophilic Methanosarcina spp isolated from full scale biogas plants treating animal manures
    FEMS Microbiology Ecology, 2000
    Co-Authors: Zuzana Mladenovska, Birgitte Kiær Ahring
    Abstract:

    This study determines the growth kinetics of thermophilic strains of Methanosarcina spp. from full-scale thermophilic biogas plants. The complete set of kinetic parameters, including maximum specific growth rate μmax, half saturation constant KS, acetate threshold concentration and cell growth yield YX/S, were determined for six Methanosarcina strains newly isolated from full-scale reactors and the type strain Methanosarcina thermophila TM-1T. The kinetic experiments were performed in media supplemented with acetate and activated carbon at the optimum growth temperatures of the individual strains, 50–55°C. The μmax values of the isolates were in the range of 0.044–0.064 h−1, the KS ranged from 6.5 to 24.7 mM acetate and the threshold for acetate utilization from 0.11 to 0.40 mM. The cell growth yields of the strains were between 0.78 and 2.97 g dry weight cells mol−1 acetate. The six isolates exhibited significantly higher μmax and had higher affinity to acetate than the type strain M. thermophila TM-1T. Generally, the affinities of thermophilic Methanosarcina strains tested in this study cover a similar range to those reported in the literature for mesophilic Methanosarcina spp. with acetate as substrate. The strains isolated from plants treating mixtures of animal manures and industrial organic wastes had higher affinity for acetate and lower thresholds than strains isolated from reactors operating solely on manures.

  • Mixotrophic growth of two thermophilic Methanosarcina strains, Methanosarcina thermophila TM-1 and Methanosarcina sp. SO-2P, on methanol and hydrogen/carbon dioxide
    Applied Microbiology and Biotechnology, 1997
    Co-Authors: Zuzana Mladenovska, Birgitte Kiær Ahring
    Abstract:

    Two thermophilic strains, Methanosarcina thermophila TM-1 and Methanosarcina sp. SO-2P, were capable of mixotrophic growth on methanol and H2/CO2. Activated carbon was, however, found to be necessary to support good growth. Both strains used hydrogen and methanol simultaneously. When methanol was depleted, hydrogen utilization continued and methane was further produced with concurrent cell growth. UV epifluorescence microscopy revealed that aggregates of both strains exhibited a bright red fluorescence besides the usual blue-green fluorescence.