Biotechnological potential of psychrotolerant methylobacteria isolated from biotopes of Antarctic oases.

Ten strains of psychrotolerant methylotrophic bacteria were isolated from the samples collected in Larsemann and Bunger Hills (Antarctica). Most of the isolates are assigned to the genus Pseudomonas, representatives of the genera Janthinobacterium, Massilia, Methylotenera and Flavobacterium were also found. Majority of isolates were able to grow on a wide range of sugars, methylamines and other substrates. Optimal growth temperatures for the isolated strains varied from 6 °C to 28 °C. The optimal concentration of NaCl was 0.5-2.0%. The optimal pH values of the medium were 6-7. It was found that three strains synthesized indole-3-acetic acid on a medium with L-tryptophan reaching 11-12 µg/ml. The values of intracellular carbohydrates in several strains exceeded 50 µg/ml. Presence of calcium-dependent and lanthanum-dependent methanol dehydrogenase have been shown for some isolates. Strains xBan7, xBan20, xBan37, xBan49, xPrg27, xPrg48, xPrg51 showed the presence of free amino acids. Bioprospection of Earth cryosphere for such microorganisms has a potential in biotechnology.

Methylotrophic bacteria from rice paddy soils: mineral-nitrogen-utilizing isolates richness in bulk soil and rhizosphere.

Methanol, the second most abundant volatile organic compound, primarily released from plants, is a major culprit disturbing atmospheric chemistry. Interestingly, ubiquitously found methanol-utilizing bacteria, play a vital role in mitigating atmospheric methanol effects. Despite being extensively characterized, the effect of nitrogen sources on the richness of methanol-utilizers in the bulk soil and rhizosphere is largely unknown. Therefore, the current study was planned to isolate, characterize and explore the richness of cultivable methylotrophs from the bulk soil and rhizosphere of a paddy field using media with varying nitrogen sources. Our data revealed that more genera of methylotrophs, including Methylobacterium, Ancylobacter, Achromobacter, Xanthobacter, Moraxella, and Klebsiella were enriched with the nitrate-based medium compared to only two genera, Hyphomicrobium and Methylobacterium, enriched with the ammonium-based medium. The richness of methylotrophic bacteria also differed substantially in the bulk soil as compared to the rhizosphere. Growth characterization revealed that majority of the newly isolated methanol-utilizing strains in this study exhibited better growth at 37 °C instead of 30 or 45 °C. Moreover, Hyphomicrobium sp. FSA2 was the only strain capable of utilizing methanol even at elevated temperature 45 °C, showing its adaptability to a wide range of temperatures. Differential carbon substrate utilization profiling revealed the facultative nature of all isolated methanol-utilizer strains with Xanthobacter sp. TS3, being an important methanol-utilizer capable of degrading toxic compounds such as acetone and ethylene glycol. Overall, our study suggests the role of nutrients and plant-microbial interaction in shaping the composition of methanol-utilizers in terrestrial environment.

Methylobacterium spp. mitigation of UV stress in mung bean (Vigna radiata L.).

Methylotrophs are a diverse group of bacteria that abundantly colonize the phyllosphere and have great potential to withstand UV irradiation because of their pigmented nature and ability to promote plant growth through various mechanisms. The present study investigated the effects of UVB radiation on plant growth-promoting (PGP) properties of methylotrophic bacteria and the growth of Vigna radiata L. A total of 55 methylotrophic bacteria were isolated from desert plants, and 15 methylotrophs were resistant to UVB radiation for 4 h. All UVB-resistant methylotrophs possess a methyldehydrogenase gene. Identification based on 16S rRNA gene sequencing revealed that all 15 UVB-resistant methylotrophs belonged to the genera Methylorubrum (07), Methylobacterium (07), and Rhodococcus (01). Screening of methylotrophs for PGP activity in the presence and absence of UVB radiation revealed that all isolates showed ACC deaminase activity and growth on a nitrogen-free medium. Furthermore, the production of IAA-like substances ranged from 8.62 to 85.76 µg/mL, siderophore production increased from 3.47 to 65.75% compared to the control. Seed germination assay with V. radiata L. (mung bean) exposed to UVB radiation revealed that methylotrophs improved seed germination, root length, and shoot length compared to the control. The present findings revealed that the isolates SD3, SD2, KD1, KD5, UK1, and UK3 reduced the deleterious effects of UVB radiation on mung bean plants and can be used to protect seedlings from UVB radiation for sustainable agriculture.

Methylotrophic Communities Associated with a Greenland Ice Sheet Methane Release Hotspot.

Subglacial environments provide conditions suitable for the microbial production of methane, an important greenhouse gas, which can be released from beneath the ice as a result of glacial melting. High gaseous methane emissions have recently been discovered at Russell Glacier, an outlet of the southwestern margin of the Greenland Ice Sheet, acting not only as a potential climate amplifier but also as a substrate for methane consuming microorganisms. Here, we describe the composition of the microbial assemblage exported in meltwater from the methane release hotspot at Russell Glacier and its changes over the melt season and as it travels downstream. We found that a substantial part (relative abundance 27.2% across the whole dataset) of the exported assemblage was made up of methylotrophs and that the relative abundance of methylotrophs increased as the melt season progressed, likely due to the seasonal development of the glacial drainage system. The methylotrophs were dominated by representatives of type I methanotrophs from the Gammaproteobacteria; however, their relative abundance decreased with increasing distance from the ice margin at the expense of type II methanotrophs and/or methylotrophs from the Alphaproteobacteria and Betaproteobacteria. Our results show that subglacial methane release hotspot sites can be colonized by microorganisms that can potentially reduce methane emissions.

Synergy effects of Methylomonas koyamae and Hyphomicrobium methylovorum under methanethiol stress.

Methanotrophs are able to metabolize volatile organic sulfur compounds (VOSCs), excrete organic carbon during CH4 oxidation, and influence microbial community structure and function of the ecosystem. In return, microbial community structure and environmental factors can affect the growth metabolism of methanotrophs. In this study, Methylomonas koyamae and Hyphomicrobium methylovorum were used for model organisms, and methanethiol (MT) was chosen for a typical VOSC to investigate the synergy effects under VOSC stress. The results showed that when Hyphomicrobium methylovorum was co-cultured with Methylomonas koyamae in the medium with CH4 used as the carbon source, the co-culture had better MT tolerance relative to Methylomonas koyamae and oxidized all CH4 within 120 h, even at the initial MT concentration of 2000 mg m-3. The optimal co-culture ratios of Methylomonas koyamae to Hyphomicrobium methylovorum were 4:1-12:1. Although MT could be converted spontaneously to dimethyl disulfide (DMDS), H2S, and CS2 in air, faster losses of MT, DMDS, H2S, and CS2 were observed in each strain mono-culture and the co-culture. Compared with Hyphomicrobium methylovorum, MT was degraded more quickly in the Methylomonas koyamae culture. During the co-culture, the CH4 oxidation process of Methylomonas koyamae could provide carbon and energy sources for the growth of Hyphomicrobium methylovorum, while Hyphomicrobium methylovorum oxidized MT to help Methylomonas koyamae detoxify. These findings are helpful to understand the synergy effects of Methylomonas koyamae and Hyphomicrobium methylovorum under MT stress and enrich the role of methanotrophs in the sulfur biogeochemical cycle. KEY POINTS: • The co-culture of Methylomonas and Hyphomicrobium has better tolerance to CH3SH. • Methylomonas can provide carbon sources for the growth of Hyphomicrobium. • The co-culture of Methylomonas and Hyphomicrobium enhances the removal of CH4 and CH3SH.

Prospect of pink pigmented facultative methylotrophs in mitigating abiotic stress and climate change.

Apparently, climate change is observed in form of increased greenhouse gases (CH4 , CO2 , N2 O, CFC), temperature (0.5-1°C), and UV radiations (UV B and UV C). It is affecting every aspect of ecosystem functioning; however, terrestrial crops are the most vulnerable group and crop productivity largely remains a challenge. Due to climate change, seed yield and nutrient depletion are inevitable in future scenarios. To overcome this problem microbial groups that exhibit plant growth promoting attributes and provide protection against environmental stress should be studied. One such group is the pink pigmented facultative methylotrophs (PPFMs) that can induce overall fitness to plants. PPFMs are involved in phosphorous mineralization, siderophore, ACC deaminase, phytohormone production, and assimilation of greenhouse gases. Additionally, these organisms can also resist harmful UV radiations effectively as they possess polyketide synthases that could serve as source of novel bioactives that can protect plant from abiotic stress. The review article comprehensively highlights the multifunctional traits of PPFMs and their role in mitigating climate change with an aim to use this important organism as microbial inoculants for sustainable agriculture under climate-changing scenarios.

Strategies and challenges with the microbial conversion of methanol to high-value chemicals.

As alternatives to traditional fermentation substrates, methanol (CH3 OH), carbon dioxide (CO2 ) and methane (CH4 ) represent promising one-carbon (C1) sources that are readily available at low-cost and share similar metabolic pathway. Of these C1 compounds, methanol is used as a carbon and energy source by native methylotrophs, and can be obtained from CO2 and CH4 by chemical catalysis. Therefore, constructing and rewiring methanol utilization pathways may enable the use of one-carbon sources for microbial fermentations. Recent bioengineering efforts have shown that both native and nonnative methylotrophic organisms can be engineered to convert methanol, together with other carbon sources, into biofuels and other commodity chemicals. However, many challenges remain and must be overcome before industrial-scale bioprocessing can be established using these engineered cell refineries. Here, we provide a comprehensive summary and comparison of methanol metabolic pathways from different methylotrophs, followed by a review of recent progress in engineering methanol metabolic pathways in vitro and in vivo to produce chemicals. We discuss the major challenges associated with establishing efficient methanol metabolic pathways in microbial cells, and propose improved designs for future engineering.

Novel outlook in engineering synthetic methylotrophs and formatotrophs: a course for advancing C1-based chemicals production.

The world is at a critical stage to switch from fossil and agriculture feedstocks with sustainable alternatives for the production of biobased chemicals of everyday use. This has spurred interest in using carbon one compounds; methanol and formate as a substrate or cosubstrate for microbial-based production. However, considering that native methylotrophs and formatotrophs utilize methanol and formate respectively, their capabilities to efficiently produce high value-added chemicals are limited. Therefore, shifting from these native C1 microbes to metabolically engineered non-native C1 model strains has attracted increasing attention thanks to many advantages such as the availability of well-established tools and strategies for metabolic engineering, and in addition to its high cell growth rate. Herein, we discussed recent trends in developing synthetic methylotrophs and formatotrophs for methanol and formate-based biomanufacturing. Finally, we highlighted barriers and provided broad prospects on possible avenues for optimizing synthetic methylotrophic and formatotrophic strains with respect to the recent advances in biology.

Complete genome sequence of Klebsiella pneumoniae RX.G5M15, a methanol-metabolizing strain recovered from the sole of a shoe.

The methanol-metabolizing strain Klebsiella pneumoniae RX.G5M15 was isolated from the sole of a shoe in Hong Kong. Its complete genome, a single chromosome and two plasmids totaling 5,381,940 bp (G+C 57.43%), was established through the hybrid assembly.

Engineering Terpene Production Pathways in Methylobacterium extorquens AM1.

Terpenes are diverse specialized metabolites naturally found within plants and have important roles in inter-species communication, adaptation and interaction with the environment. Their industrial applications span a broad range, including fragrances, flavors, cosmetics, natural colorants to agrochemicals and therapeutics, yet formal chemical synthesis is economically challenging due to structural complexities. Engineering terpene biosynthesis could represent an alternative in microbial biotechnological workhorses, such as Saccharomyces cerevisiae or Escherichi coli, utilizing sugars or complex media as feedstocks. Host species that metabolize renewable and affordable carbon sources may offer unique sustainable biotechnological alternatives. Methylotrophs are bacteria with the capacity to utilize one-carbon feedstocks, such as methanol or formate. They colonize the phyllosphere (above-ground area) of plants, and many accumulate abundant carotenoid pigments. Methylotrophs have the capacity to take up and use a subset of the rare earth elements known as lanthanides. These metals can enhance one-carbon (methylotrophic) metabolism. Here, we investigated whether manipulating the metabolism enables and enhances terpene production. A carotenoid-deficient mutant potentially liberates carbon, which may contribute to bioproduct accumulation. To test this hypothesis, terpene-producing bacterial strains regulated by two distinct promoters were generated. Wildtype Methylobacterium extorquens, ∆Meta1_3665, a methylotrophic mutant lacking the carotenoid pathway, and an E. coli strain were transformed with an exogenous terpene pathway and grown both in the presence and absence of lanthanides. The extraction, and the comparison of analytical profiles, provided evidence that engineered cultured M. extorquens under control of a native, inducible methylotrophic promoter can yield the sesquiterpene patchoulol when supplemented with lanthanide. In contrast, using a moderate-strength constitutive promoter failed to give production. We demonstrated colonization of the phyllosphere with the engineered strains, supporting the future engineering of selected species of the plant microbiome and with promising implications for the synthetic biology of small molecules.

Industrial and Pharmaceutical Applications of Microbial Diversity of Hypersaline Ecology from Lonar Soda Crater.

The unidentified geochemical and physiochemical characteristics of Soda Lakes across the globe make it a novel reservoir and bring attention to scientific civic for its conceivable industrial and pharmaceutical applications. In India, in the Maharashtra state, Lonar Lake is a naturally created Soda Lake by a meteorite impact. Phylogenetic data from this lake explored a diverse array of microorganisms like haloalkaliphilic bacteria and Archaea. Previously reported studies postulated the major microbial communities present in this lake ecosystem are Proteobacteria, Actinobacteria, Firmicutes, and Cyanobacteria. Furthermore, it also contains Bacteroidetes, Nitrospirae, and Verrucomicrobia. This lake is also rich in phytoplankton, with the predominant presence of the Spirulina plantensis. Unique microbial strains from Lonar Lake ecosystems have fascinated consideration as a source of biological molecules with medicinal, industrial, and biotechnological potential. Recent literature revealed the isolation of antibioticproducing bacteria and alkaline proteases-producing alkaliphilic bacterium, as well as novel species of rare methylotrophs, other bacterial strains involved in producing vital enzymes, and unique actinomycetes are also reported. It indicates that the novel bacterial assemblage not reached hitherto may exist in this modified and unique ecology. This comprehensive review provides information about microbial diversity and its industrial and pharmaceutical interests that exist in Lonar Lake, which could be the future source of bioactive enzymes, biosurfactants, and biofuel and also useful in bioremediation. Furthermore, the novel species of microorganisms isolated from Lonar Lake have applications in the biosynthesis of medicines like antibiotics, antivirals, antifungals, anti-inflammatory agents, and precursors for synthesising valuable products. Data consolidated in the present review will cater to the needs of emerging industrial sectors for their commercial and therapeutic applications.

Genomic Insights into the Landfill Microbial Community: Denitrifying Activity Supporting One-Carbon Utilization.

In spite of the developments in understanding of denitrifying methylotrophy in the recent years, challenges still exist in unravelling the overall biochemistry of nitrate-dependent methane oxidation in novel or poorly characterized/not-yet-cultured bacteria. In the present study, landfill site was mined for novel C1-carbon-metabolizing bacteria which can use nitrate/nitrite as an electron acceptor. A high-throughput rapid plate assay identified three bacterial isolates with eminent ability for nitrate-dependent methane metabolism under anaerobic conditions. Taxonomic identification by whole-genome sequence-based overall genome relatedness indices accurately assigned the isolates AAK_M13, AAK_M29, and AAK_M39 at the species level to Enterobacter cloacae, Bacillus subtilis, and Bacillus halotolerans, respectively. Several genes encoding sub-components involved in alcohol utilization and denitrification pathways, such as adh, fdh, fdo, nar, nir, and nor, were identified in all the genomes. Though no gene clusters encoding MMO/AMO were annotated, sequencing of PCR amplicons revealed similarity with pMMO/AMO gene using translated nucleotide sequence of strains AAK_M29 and AAK_M39, while strain AAK_M13 showed similarity with XRE family transcriptional regulator. This suggests the horizontal gene transfer and/or presence of a truncated version of a housekeeping enzyme encoded by genes exhibiting partial sequence similarity with pMMO genes that mimicked its function at greenhouse gas emission sites. Owing to lack of conclusive evidence for presence of methane metabolism genes in the selected isolates, further experiment was performed to validate their nitrate-dependent methane oxidation capacities. Bacillus subtilis AAK_M29, Bacillus halotolerans AAK_M39, and Enterobacter cloacae AAK_M13 could oxidize 60%, 75%, and 85% of the added methane respectively accompanied by high nitrate reduction (56-62%) thus supporting the correlation between these two activities. The remarkable ability of these isolates for nitrate-dependent methane metabolism has highlighted their role in ecological contribution and biotechnological potential to serve as methane and nitrate sinks in the landfill sites.

Methane-oxidizing bacterial community dynamics in sub-alpine forest soil.

Microbial activities in sub-alpine forest soil influence global cycling of the potent greenhouse gas methane. Understanding the dynamics of methane-oxidizing bacterial communities, particularly the roles of potentially active versus total microbial populations, is necessary for reducing uncertainty in global methane budget estimates. However, our understanding of the factors influencing methane cycling in forest soils is limited by our lack of knowledge about the biology of the microbes involved and how these communities are shaped by their environment. Here, we compared the composition and potential activity of microbial communities using 16S rRNA gene amplicon sequencing of total genomic DNA (gDNA) and potentially active complementary DNA (cDNA) from shallow soil in Red Butte Canyon (Salt Lake City, Utah, USA). We compared riparian and upland soils at two time points in the growing season and found distinct differences in both the community composition of the gDNA and cDNA libraries and the potential drivers of these community structures. Aerobic methane-oxidizing bacteria (methanotrophs) were detected in all samples, with cDNA libraries containing a higher average relative abundance and diversity of methanotrophs compared to gDNA libraries. Methane flux at the sample sites did not significantly correlate to the relative abundance (gDNA) or potential activity (cDNA) of methanotrophs. In the cDNA libraries, there were significant positive correlations between the abundance of Methylococcaceae family methanotrophs and several non-methanotrophic methylotrophs previously found to be associated with methane-oxidizing bacterial communities. These findings suggest a complex relationship between methane-cycling bacterial communities and methane flux and highlight the need for further in situ studies to understand the environmental and ecological influences of these microbial consortia. IMPORTANCE: Methane-oxidizing bacteria are found in diverse soil and sediment environments and play an important role in mitigating flux of this potent greenhouse gas into the atmosphere. However, it is unclear how these bacteria and their associated communities are structured in the environment and how their activity ultimately influences methane flux. In this work, we examine the composition and structure of methane-oxidizing bacterial communities in sub-alpine forest soil and find soil- and time-specific differences between the stable and potentially active populations. We also find that the potentially active populations of certain methanotrophs and non-methanotrophs are positively correlated. This work provides a step toward refining our understanding of microbially mediated biogeochemical cycles.

Complete genome sequence of Kosakonia pseudosacchari RX.G5M8, a putative methylotroph isolated from Hong Kong soil.

Kosakonia pseudosacchari RX.G5M8, a putative methylotroph, was isolated from garden soil in Hong Kong. Its complete genome, a single chromosome of 4,953,935 bp (GC content 53.91%), was established through hybrid assembly.

[Advances in biotransformation of methanol into chemicals].

Methanol has become an attractive substrate for the biomanufacturing industry due to its abundant supply and low cost. The biotransformation of methanol to value-added chemicals using microbial cell factories has the advantages of green process, mild conditions and diversified products. These advantages may expand the product chain based on methanol and alleviate the current problem of biomanufacturing, which is competing with people for food. Elucidating the pathways involving methanol oxidation, formaldehyde assimilation and dissimilation in different natural methylotrophs is essential for subsequent genetic engineering modification, and is more conducive to the construction of novel non-natural methylotrophs. This review discusses the current status of research on methanol metabolic pathways in methylotrophs, and presents recent advances and challenges in natural and synthetic methylotrophs and their applications in methanol bioconversion.

Methanol-based biomanufacturing of fuels and chemicals using native and synthetic methylotrophs.

Methanol has recently gained significant attention as a potential carbon substrate for the production of fuels and chemicals, owing to its high degree of reduction, abundance, and low price. Native methylotrophic yeasts and bacteria have been investigated for the production of fuels and chemicals. Alternatively, synthetic methylotrophic strains are also being developed by reconstructing methanol utilization pathways in model microorganisms, such as Escherichia coli. Owing to the complex metabolic pathways, limited availability of genetic tools, and methanol/formaldehyde toxicity, the high-level production of target products for industrial applications are still under development to satisfy commercial feasibility. This article reviews the production of biofuels and chemicals by native and synthetic methylotrophic microorganisms. It also highlights the advantages and limitations of both types of methylotrophs and provides an overview of ways to improve their efficiency for the production of fuels and chemicals from methanol.

Graphene as Thinnest Coating on Copper Electrodes in Microbial Methanol Fuel Cells.

Dehydrogenation of methanol (CH3OH) into direct current (DC) in fuel cells can be a potential energy conversion technology. However, their development is currently hampered by the high cost of electrocatalysts based on platinum and palladium, slow kinetics, the formation of carbon monoxide intermediates, and the requirement for high temperatures. Here, we report the use of graphene layers (GL) for generating DC electricity from microbially driven methanol dehydrogenation on underlying copper (Cu) surfaces. Genetically tractable Rhodobacter sphaeroides 2.4.1 (Rsp), a nonarchetypical methylotroph, was used for dehydrogenating methanol at the GL-Cu surfaces. We use electrochemical methods, microscopy, and spectroscopy methods to assess the effects of GL on methanol dehydrogenation by Rsp cells. The GL-Cu offers a 5-fold higher power density and 4-fold higher current density compared to bare Cu. The GL lowers charge transfer resistance to methanol dehydrogenation by 4 orders of magnitude by mitigating issues related to pitting corrosion of underlying Cu surfaces. The presented approach for catalyst-free methanol dehydrogenation on copper electrodes can improve the overall sustainability of fuel cell technologies.

Secondary metabolites from methylotrophic bacteria: their role in improving plant growth under a stressed environment.

Climate change is considered a natural disaster that causes the ecosystem to fluctuate and increase temperature, as well as the amount of UV radiation (UV-A and UV-B) on the Earth's surface. Consequently, greenhouse gases such as chlorofluorocarbons, methane, nitrogen oxide, and carbon dioxide have become obstacles to the development of sustainable agriculture. To overcome environmental stress such as phytopathogens, drought, salinity, heavy metals, and high-low temperatures, the utilization of microorganisms is a viable option. The synthesis of secondary metabolites by methylotrophic bacteria improves plant metabolism, enhances tolerance, and facilitates growth. The genus Methylobacterium is a pink-pigmented facultative methylotrophs which abundantly colonizes plants, especially young leaves, owing to the availability of methanol. Secondary metabolites such as amino acids, carotenoids, hormones, antimicrobial compounds, and other compounds produced by methylotrophic bacteria enhance plant metabolism under stress conditions. Therefore, in this review, we discuss the role of secondary metabolites produced by methylotrophic bacteria and their role in promoting plant growth under stress.

Enzymatic properties of alcohol dehydrogenase PedE_M.s. derived from Methylopila sp. M107 and its broad metal selectivity.

As an important metabolic enzyme in methylotrophs, pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenases play significant roles in the global carbon and nitrogen cycles. In this article, a calcium (Ca2+)-dependent alcohol dehydrogenase PedE_M.s., derived from the methylotroph Methylopila sp. M107 was inserted into the modified vector pCM80 and heterologously expressed in the host Methylorubrum extorquens AM1. Based on sequence analysis, PedE_M.s., a PQQ-dependent dehydrogenase belonging to a methanol/ethanol family, was successfully extracted and purified. Showing by biochemical results, its enzymatic activity was detected as 0.72 U/mg while the Km value was 0.028 mM while employing ethanol as optimal substrate. The activity of PedE_M.s. could be enhanced by the presence of potassium (K+) and calcium (Ca2+), while acetonitrile and certain common detergents have been found to decrease the activity of PedE_M.s.. In addition, its optimum temperature and pH were 30°C and pH 9.0, respectively. Chiefly, as a type of Ca2+-dependent alcohol dehydrogenase, PedE_M.s. maintained 60-80% activity in the presence of 10 mM lanthanides and displayed high affinity for ethanol compared to other PedE-type enzymes. The 3D structure of PedE_M.s. was predicted by AlphaFold, and it had an 8-bladed propeller-like super-barrel. Meanwhile, we could speculate that PedE_M.s. contained the conserved residues Glu213, Asn300, and Asp350 through multiple sequence alignment by Clustal and ESpript. The analysis of enzymatic properties of PedE_M.s. enriches our knowledge of the methanol/ethanol family PQQ-dependent dehydrogenase. This study provides new ideas to broaden the application of alcohol dehydrogenase in alcohol concentration calculation, biosensor preparation, and other industries.

Methyl-Based Methanogenesis: an Ecological and Genomic Review.

Methyl-based methanogenesis is one of three broad categories of archaeal anaerobic methanogenesis, including both the methyl dismutation (methylotrophic) pathway and the methyl-reducing (also known as hydrogen-dependent methylotrophic) pathway. Methyl-based methanogenesis is increasingly recognized as an important source of methane in a variety of environments. Here, we provide an overview of methyl-based methanogenesis research, including the conditions under which methyl-based methanogenesis can be a dominant source of methane emissions, experimental methods for distinguishing different pathways of methane production, molecular details of the biochemical pathways involved, and the genes and organisms involved in these processes. We also identify the current gaps in knowledge and present a genomic and metagenomic survey of methyl-based methanogenesis genes, highlighting the diversity of methyl-based methanogens at multiple taxonomic levels and the widespread distribution of known methyl-based methanogenesis genes and families across different environments.