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Nature Communications Feb 2018The detection of silica-rich dust particles, as an indication for ongoing hydrothermal activity, and the presence of water and organic molecules in the plume of...
The detection of silica-rich dust particles, as an indication for ongoing hydrothermal activity, and the presence of water and organic molecules in the plume of Enceladus, have made Saturn's icy moon a hot spot in the search for potential extraterrestrial life. Methanogenic archaea are among the organisms that could potentially thrive under the predicted conditions on Enceladus, considering that both molecular hydrogen (H) and methane (CH) have been detected in the plume. Here we show that a methanogenic archaeon, Methanothermococcus okinawensis, can produce CH under physicochemical conditions extrapolated for Enceladus. Up to 72% carbon dioxide to CH conversion is reached at 50 bar in the presence of potential inhibitors. Furthermore, kinetic and thermodynamic computations of low-temperature serpentinization indicate that there may be sufficient H gas production to serve as a substrate for CH production on Enceladus. We conclude that some of the CH detected in the plume of Enceladus might, in principle, be produced by methanogens.
Topics: Atmosphere; Atmospheric Pressure; Exobiology; Extraterrestrial Environment; Hydrogen; Methane; Methanobacteriaceae; Methanococcaceae; Methanococcus; Models, Biological; Saturn; Spacecraft
PubMed: 29487311
DOI: 10.1038/s41467-018-02876-y -
Biochimica Et Biophysica Acta Aug 1999Schrödinger stated in his landmark book, What is Life?, that life feeds on negative entropy. In this contribution, the validity of this statement is discussed through a... (Review)
Review
Schrödinger stated in his landmark book, What is Life?, that life feeds on negative entropy. In this contribution, the validity of this statement is discussed through a careful thermodynamic analysis of microbial growth processes. In principle, both feeding on negative entropy, i.e. yielding products of higher entropy than the substrates, and generating heat can be used by microorganisms to rid themselves of internal entropy production resulting from maintenance and growth processes. Literature data are reviewed in order to compare these two mechanisms. It is shown that entropy-neutral, entropy-driven, and entropy-retarded growth exist. The analysis of some particularly interesting microorganisms shows that enthalpy-retarded microbial growth may also exist, which would signify a net uptake of heat during growth. However, the existence of endothermic life has never been demonstrated in a calorimeter. The internal entropy production in live cells also reflects itself in the Gibbs energy dissipation accompanying growth, which is related quantitatively to the biomass yield. An empirical correlation of the Gibbs energy dissipation in terms of the physico-chemical nature of the growth substrate has been proposed in the literature and can be used to predict the biomass yield approximately. The ratio of enthalpy change and Gibbs energy change can also be predicted since it is shown to be approximately equal to the same ratio of the relevant catabolic process alone.
Topics: Aerobiosis; Anaerobiosis; Bacteria; Kluyveromyces; Methanobacterium; Saccharomyces cerevisiae; Thermodynamics; Yeasts
PubMed: 10482783
DOI: 10.1016/s0005-2728(99)00065-1 -
Scientific Reports Dec 2019Archaeal sequences have been detected in human colostrum and milk, but no studies have determined whether living archaea are present in either of these fluids....
Archaeal sequences have been detected in human colostrum and milk, but no studies have determined whether living archaea are present in either of these fluids. Methanogenic archaea are neglected since they are not detected by usual molecular and culture methods. By using improved DNA detection protocols and microbial culture techniques associated with antioxidants previously developed in our center, we investigated the presence of methanogenic archaea using culture and specific Methanobrevibacter smithii and Methanobrevibacter oralis real-time PCR in human colostrum and milk. M. smithii was isolated from 3 colostrum and 5 milk (day 10) samples. M. oralis was isolated from 1 milk sample. For 2 strains, the genome was sequenced, and the rhizome was similar to that of strains previously isolated from the human mouth and gut. M. smithii was detected in the colostrum or milk of 5/13 (38%) and 37/127 (29%) mothers by culture and qPCR, respectively. The different distribution of maternal body mass index according to the detection of M. smithii suggested an association with maternal metabolic phenotype. M. oralis was not detected by molecular methods. Our results suggest that breastfeeding may contribute to the vertical transmission of these microorganisms and may be essential to seed the infant's microbiota with these neglected critical commensals from the first hour of life.
Topics: Animals; Body Mass Index; Breast Feeding; Chemoautotrophic Growth; Colostrum; DNA, Archaeal; Euryarchaeota; Feces; Female; Humans; Infant; Methanobrevibacter; Microbiota; Milk, Human; Mothers; Pregnancy
PubMed: 31819085
DOI: 10.1038/s41598-019-54759-x -
Scientific Reports May 2017Anaerobic digesters are man-made habitats for fermentative and methanogenic microbes, and are characterized by extremely high concentrations of organics. However, little...
Anaerobic digesters are man-made habitats for fermentative and methanogenic microbes, and are characterized by extremely high concentrations of organics. However, little is known about how microbes adapt to such habitats. In the present study, we report phylogenetic, metagenomic, and metatranscriptomic analyses of microbiomes in thermophilic packed-bed digesters fed acetate as the major substrate, and we have shown that acetoclastic and hydrogenotrophic methanogens that utilize acetate as a carbon source dominate there. Deep sequencing and precise binning of the metagenomes reconstructed complete genomes for two dominant methanogens affiliated with the genera Methanosarcina and Methanothermobacter, along with 37 draft genomes. The reconstructed Methanosarcina genome was almost identical to that of a thermophilic acetoclastic methanogen Methanosarcina thermophila TM-1, indicating its cosmopolitan distribution in thermophilic digesters. The reconstructed Methanothermobacter (designated as Met2) was closely related to Methanothermobacter tenebrarum, a non-autotrophic hydrogenotrophic methanogen that grows in the presence of acetate. Met2 lacks the Cdh complex required for CO fixation, suggesting that it requires organic molecules, such as acetate, as carbon sources. Although the metagenomic analysis also detected autotrophic methanogens, they were less than 1% in abundance of Met2. These results suggested that non-autotrophic methanogens preferentially grow in anaerobic digesters containing high concentrations of organics.
Topics: Anaerobiosis; Autotrophic Processes; Bioreactors; Contig Mapping; Genes, Archaeal; Methane; Methanobacteriaceae; Methanosarcina; Phylogeny; RNA, Ribosomal, 16S
PubMed: 28473726
DOI: 10.1038/s41598-017-01752-x -
Gut Microbes Dec 2023Methanogens, reductive acetogens and sulfate-reducing bacteria play an important role in disposing of hydrogen in gut ecosystems. However, how they interact with each...
Methanogens, reductive acetogens and sulfate-reducing bacteria play an important role in disposing of hydrogen in gut ecosystems. However, how they interact with each other remains largely unknown. This study cocultured (reductive acetogen), (sulfate reducer) and (methanogen). Results revealed that these three species coexisted and did not compete for hydrogen in the early phase of incubations. Sulfate reduction was not affected by and . inhibited the growth of and after 10 h incubations, and the inhibition on was associated with increased sulfide concentration. Remarkably, growth lag phase was shortened by coculturing with and . Formate was rapidly used by under high acetate concentration. Overall, these findings indicated that the interactions of the hydrogenotrophic microbes are condition-dependent, suggesting their interactions may vary in gut ecosystems.
Topics: Methanobrevibacter; Ecosystem; Gastrointestinal Microbiome; Hydrogen; Sulfates
PubMed: 37753963
DOI: 10.1080/19490976.2023.2261784 -
Microbiome Aug 2022Carbon fixation through biological methanation has emerged as a promising technology to produce renewable energy in the context of the circular economy. The anaerobic...
BACKGROUND
Carbon fixation through biological methanation has emerged as a promising technology to produce renewable energy in the context of the circular economy. The anaerobic digestion microbiome is the fundamental biological system operating biogas upgrading and is paramount in power-to-gas conversion. Carbon dioxide (CO) methanation is frequently performed by microbiota attached to solid supports generating biofilms. Despite the apparent simplicity of the microbial community involved in biogas upgrading, the dynamics behind most of the interspecies interaction remain obscure. To understand the role of the microbial species in CO fixation, the biofilm generated during the biogas upgrading process has been selected as a case study. The present work investigates via genome-centric metagenomics, based on a hybrid Nanopore-Illumina approach the biofilm developed on the diffusion devices of four ex situ biogas upgrading reactors. Moreover, genome-guided metabolic reconstruction and flux balance analysis were used to propose a biological role for the dominant microbes.
RESULTS
The combined microbiome was composed of 59 species, with five being dominant (> 70% of total abundance); the metagenome-assembled genomes representing these species were refined to reach a high level of completeness. Genome-guided metabolic analysis appointed Firmicutes sp. GSMM966 as the main responsible for biofilm formation. Additionally, species interactions were investigated considering their co-occurrence in 134 samples, and in terms of metabolic exchanges through flux balance simulation in a simplified medium. Some of the most abundant species (e.g., Limnochordia sp. GSMM975) were widespread (~ 67% of tested experiments), while others (e.g., Methanothermobacter wolfeii GSMM957) had a scattered distribution. Genome-scale metabolic models of the microbial community were built with boundary conditions taken from the biochemical data and showed the presence of a flexible interaction network mainly based on hydrogen and carbon dioxide uptake and formate exchange.
CONCLUSIONS
Our work investigated the interplay between five dominant species within the biofilm and showed their importance in a large spectrum of anaerobic biogas reactor samples. Flux balance analysis provided a deeper insight into the potential syntrophic interaction between species, especially Limnochordia sp. GSMM975 and Methanothermobacter wolfeii GSMM957. Finally, it suggested species interactions to be based on formate and amino acids exchanges. Video Abstract.
Topics: Anaerobiosis; Biofuels; Bioreactors; Carbon Dioxide; Firmicutes; Formates; Metagenome; Methane; Methanobacteriaceae
PubMed: 35918706
DOI: 10.1186/s40168-022-01311-1 -
BMC Microbiology Dec 2018Tibetan sheep (TS) and Gansu Alpine Finewool sheep (GS) are both important plateau sheep raised and fed on the harsh Qinghai-Tibetan Plateau, China. Rumen methanogen and...
BACKGROUND
Tibetan sheep (TS) and Gansu Alpine Finewool sheep (GS) are both important plateau sheep raised and fed on the harsh Qinghai-Tibetan Plateau, China. Rumen methanogen and protozoal communities of plateau sheep are affected by their hosts and living environments, and play important roles in ruminant nutrition and greenhouse gas production. However, the characteristics, differences, and associations of these communities remain largely uncharacterized.
RESULTS
The rumen methanogen and protozoal communities of plateau sheep were investigated by 16S/18S rRNA gene clone libraries. The predominant methanogen order in both sheep species was Methanobacteriales followed by Methanomassiliicoccales, which is consistent with those seen in global ruminants. However, the most dominant species was Methanobrevibacter millerae rather than Methanobrevibacter gottschalkii seen in most ruminants. Compared with GS and other ruminants, TS have more exclusive operational taxonomic units and a lower proportion (64.5%) of Methanobrevibacter. The protozoa were divided into Entodiniomorphida and Vestibuliferida, including nine genera and 15 species. The proportion of holotrich protozoa was much lower (1.1%) in TS than ordinary sheep. The most predominant genus was Entodinium (70.0%) in TS and Enoploplastron (48.8%) in GS, while the most common species was Entodinium furca monolobum (43.9%) and Enoploplastron triloricatum (45.0%) in TS and GS, respectively; Entodinium longinucleatum (22.8%) was only observed in TS. LIBSHUFF analysis indicated that the methanogen communities of TS were significantly different from those of GS, but no significant differences were found in protozoal communities.
CONCLUSION
Plateau sheep have coevolved with unique rumen methanogen and protozoal communities to adapt to harsh plateau environments. Moreover, the host appears to have a greater influence on rumen methanogen communities than on rumen protozoal communities. The observed associations of methanogens and protozoa, together with the findings of previous studies on methane emissions from ruminant livestock, revealed that the lower proportion of Methanobrevibacter and holotrich protozoa may be responsible for the lower methane emission of TS. These findings facilitate our understanding of the rumen microbial ecosystem in plateau sheep, and could help the development of new strategies to manipulate rumen microbes to improve productivity and reduce the emission of greenhouse gases.
Topics: Animals; Euryarchaeota; Feeding Behavior; Methane; Methanobrevibacter; Phylogeny; Rumen; Sheep; Tibet; Trichostomatida
PubMed: 30545295
DOI: 10.1186/s12866-018-1351-0 -
Clinical Microbiology and Infection :... Sep 2012This work represents an update of knowledge regarding the detection methods for human microbiome-associated archaea. Despite the fact that, during the last three... (Review)
Review
This work represents an update of knowledge regarding the detection methods for human microbiome-associated archaea. Despite the fact that, during the last three decades, only four methanoarchaeal species have been isolated from the human mucosa, including faeces, subgingival plaque, and vaginal mucosa (Methanobrevibacter smithii, Methanosphaera stadtmanae, Methanobrevibacter oralis and, most recently, 'Methanomassiliicoccus luminyensis'), molecular studies, including PCR and metagenomic analyses, have detected DNA sequences indicative of the presence of additional methanoarchaea, as well as non-methanogenic archaea, in the human intestinal tract. Opinion is divided on the roles (if any) of these organisms in human disease, and certainly the data are still unclear. Future research and recently reported data highlighting the antimicrobial susceptibility of the human methanoarchaea could help in the design of selective media to discover additional human mucosa-associated archaea and ascertain their role in human infections involving complex flora.
Topics: Archaea; Feces; Humans; Metagenome; Methanobacteriaceae; Microbiological Techniques; Mucous Membrane
PubMed: 22897827
DOI: 10.1111/j.1469-0691.2012.03952.x -
Nature Communications Sep 2023Hybrid cluster proteins (HCPs) are Fe-S-O cluster-containing metalloenzymes in three distinct classes (class I and II: monomer, III: homodimer), all of which...
Hybrid cluster proteins (HCPs) are Fe-S-O cluster-containing metalloenzymes in three distinct classes (class I and II: monomer, III: homodimer), all of which structurally related to homodimeric Ni, Fe-carbon monoxide dehydrogenases (CODHs). Here we show X-ray crystal structure of class III HCP from Methanothermobacter marburgensis (Mm HCP), demonstrating its homodimeric architecture structurally resembles those of CODHs. Also, despite the different architectures of class III and I/II HCPs, [4Fe-4S] and hybrid clusters are found in equivalent positions in all HCPs. Structural comparison of Mm HCP and CODHs unveils some distinct features such as the environments of their homodimeric interfaces and the active site metalloclusters. Furthermore, structural analysis of Mm HCP C67Y and characterization of several Mm HCP variants with a Cys67 mutation reveal the significance of Cys67 in protein structure, metallocluster binding and hydroxylamine reductase activity. Structure-based bioinformatics analysis of HCPs and CODHs provides insights into the structural evolution of the HCP/CODH superfamily.
Topics: Carbon Monoxide; Computational Biology; Metalloproteins; Methanobacteriaceae; Mutation; Synapsins
PubMed: 37709776
DOI: 10.1038/s41467-023-41289-4 -
ACS Chemical Biology May 2010Isoprenoid compounds are ubiquitous in nature, participating in important biological phenomena such as signal transduction, aerobic cellular respiration, photosynthesis,...
Isoprenoid compounds are ubiquitous in nature, participating in important biological phenomena such as signal transduction, aerobic cellular respiration, photosynthesis, insect communication, and many others. They are derived from the 5-carbon isoprenoid substrates isopentenyl diphosphate (IPP) and its isomer dimethylallyl diphosphate (DMAPP). In Archaea and Eukarya, these building blocks are synthesized via the mevalonate pathway. However, the genes required to convert mevalonate phosphate (MP) to IPP are missing in several species of Archaea. An enzyme with isopentenyl phosphate kinase (IPK) activity was recently discovered in Methanocaldococcus jannaschii (MJ), suggesting a departure from the classical sequence of converting MP to IPP. We have determined the high-resolution crystal structures of isopentenyl phosphate kinases in complex with both substrates and products from Thermoplasma acidophilum (THA), as well as the IPK from Methanothermobacter thermautotrophicus (MTH), by means of single-wavelength anomalous diffraction (SAD) and molecular replacement. A histidine residue (His50) in THA IPK makes a hydrogen bond with the terminal phosphates of IP and IPP, poising these molecules for phosphoryl transfer through an in-line geometry. Moreover, a lysine residue (Lys14) makes hydrogen bonds with nonbridging oxygen atoms at P(alpha) and P(gamma) and with the P(beta)-P(gamma) bridging oxygen atom in ATP. These interactions suggest a transition-state-stabilizing role for this residue. Lys14 is a part of a newly discovered "lysine triangle" catalytic motif in IPKs that also includes Lys5 and Lys205. Moreover, His50, Lys5, Lys14, and Lys205 are conserved in all IPKs and can therefore serve as fingerprints for identifying new homologues.
Topics: Amino Acid Sequence; Archaeal Proteins; Binding Sites; Biosynthetic Pathways; Crystallography, X-Ray; Hemiterpenes; Hydrogen Bonding; Methanobacteriaceae; Models, Molecular; Protein Conformation; Protein Kinases; Protein Structure, Secondary; Protein Structure, Tertiary; Sequence Homology, Amino Acid; Thermoplasma
PubMed: 20402538
DOI: 10.1021/cb100032g