Thermotolerant Methanotrophic Bacteria from Sediments of the River Chernaya,Crimea, and Assessment of Their Growth Characteristics

Microbiology - The technology of single-cell protein production from natural gas is based on using thermotolerant methanotrophic bacteria with high growth rates on methane. So far, the spectrum of...     

Gammaproteobacterial Methanotrophs Dominate Cold Methane Seeps in Floodplains of West Siberian Rivers

A complex system of muddy fluid-discharging and methane (CH₄)-releasing seeps was discovered in a valley of the river Mukhrinskaya, one of the small rivers of the Irtysh Basin, West Siberia. CH₄ flux from most (90%) of these gas ebullition sites did not exceed 1.45 g CH₄ h⁻¹, while some seeps emitted up to 5.54 g CH₄ h⁻¹. The δ¹³C value of methane released from these seeps varied between −71.1 and −71.3‰, suggesting its biogenic origin. Although the seeps were characterized by low in situ temperatures (3.5 to 5°C), relatively high rates of methane oxidation (15.5 to 15.9 nmol CH₄ ml⁻¹ day⁻¹) were measured in mud samples. Fluorescence in situ hybridization detected 10⁷ methanotrophic bacteria (MB) per g of mud (dry weight), which accounted for up to 20.5% of total bacterial cell counts. Most (95.8 to 99.3%) methanotroph cells were type I (gammaproteobacterial) MB. The diversity of methanotrophs in this habitat was further assessed by pyrosequencing of pmoA genes, encoding particulate methane monooxygenase. A total of 53,828 pmoA gene sequences of seep-inhabiting methanotrophs were retrieved and analyzed. Nearly all of these sequences affiliated with type I MB, including the Methylobacter-Methylovulum-Methylosoma group, lake cluster 2, and several as-yet-uncharacterized methanotroph clades. Apparently, microbial communities attenuating methane fluxes from these local but strong CH₄ sources in floodplains of high-latitude rivers have a large proportion of potentially novel, psychrotolerant methanotrophs, thereby providing a challenge for future isolation studies.     

Analysis of the Complete Genome Sequence of Strain Concept-8, a Novel Representative of the Genus Methylococcus

Microbiology - The complete genome sequence of a thermotolerant obligate methanotroph Methylococcus sp. Concept-8 was determined and analyzed. This strain was obtained by long-term storage,...     

Methanotrophic bacteria in cold seeps of the floodplains of northern rivers

Small mud volcanoes (cold seeps), which are common in the floodplains of northern rivers, are potentially important (although poorly studied) sources of atmospheric methane. Field research on the cold seeps of the Mukhrina River (Khanty-Mansiysk Autonomous okrug, Russia) revealed methane fluxes from these structures to be orders of magnitude higher than from equivalent areas of the mid-taiga bogs. Microbial communities developing around the seeps were formed under conditions of high methane concentrations, low temperatures (3–5°C), and near-neutral pH. Molecular identification of methane-oxidizing bacteria from this community by analysis of the pmoA gene encoding particulate methane monooxygenase revealed both type I and type II methanotrophs (classes Gammaproteobacteria and Alphaproteobacteria, respectively), with prevalence of type I methanotrophs. Among the latter, microorganisms related to Methylobacter psychrophilus and Methylobacter tundripaludum, Crenothrix polyspora (a stagnant water dweller), and a number of methanotrophs belonging to unknown taxa were detected. Growth characteristics of two methanotrophic isolates were determined. Methylobacter sp. CMS7 exhibited active growth at 4–10°C, while Methylocystis sp. SB12 grew better at 20°C. Experimental results confirmed the major role of methanotrophic gammaproteobacteria in controlling the methane emission from cold river seeps.     

Genome Editing in Methanotrophic Bacteria: Potential Targets and Available Tools

Microbiology - Aerobic methanotrophic bacteria are prokaryotic microorganisms possessing methane monooxygenases, unique enzymes that determine their ability to utilize methane (CH4) as a growth...     

Molecular Analysis of the Microbial Community Developing in Continuous Culture of Methylococcus sp. Concept-8 on Natural Gas

Microbiology - The composition of the microbial community formed in the course of long-term (over 60 days) continuous cultivation of an obligate methanotroph Methylococcus sp. Concept-8 on natural...     

Methane-fed microbial microcosms show differential community dynamics and pinpoint taxa involved in communal response

We report observations on the dynamics of bacterial communities in response to methane stimulus in laboratory microcosm incubations prepared with lake sediment samples. We first measured taxonomic compositions of long-term enrichment cultures and determined that, although dominated by Methylococcaceae types, these cultures also contained accompanying types belonging to a limited number of bacterial taxa, methylotrophs and non-methylotrophs. We then followed the short-term community dynamics, in two oxygen tension regimens (150 μM and 15 μM), observing rapid loss of species diversity. In all microcosms, a single type of Methylobacter represented the major methane-oxidizing partner. The accompanying members of the communities revealed different trajectories in response to different oxygen tensions, with Methylotenera species being the early responders to methane stimulus under both conditions. The communities in both conditions were convergent in terms of their assemblage, suggesting selection for specific taxa. Our results support prior observations from metagenomics on distribution of carbon from methane among diverse bacterial populations and further suggest that communities are likely responsible for methane cycling, rather than a single type of microbe.