Abstract
Methanosarcina species are the most metabolically versatile of the methanogenic Archaea and can obtain energy for growth by producing methane via the hydrogenotrophic, acetoclastic or methylotrophic pathways. Methanosarcina barkeri CM1 was isolated from the rumen of a New Zealand Friesian cow grazing a ryegrass/clover pasture, and its genome has been sequenced to provide information on the phylogenetic diversity of rumen methanogens with a view to developing technologies for methane mitigation. The 4.5 Mb chromosome has an average G + C content of 39 %, and encodes 3523 protein-coding genes, but has no plasmid or prophage sequences. The gene content is very similar to that of M. barkeri Fusaro which was isolated from freshwater sediment. CM1 has a full complement of genes for all three methanogenesis pathways, but its genome shows many differences from those of other sequenced rumen methanogens. Consequently strategies to mitigate ruminant methane need to include information on the different methanogens that occur in the rumen.Electronic supplementary materialThe online version of this article (doi:10.1186/s40793-015-0038-5) contains supplementary material, which is available to authorized users.
Highlights
Ruminants are foregut fermenters and have evolved an efficient digestive system in which microbes ferment plant fibre and provide fermentation end-products and other nutrients for growth of the animal [1]
The 16S rRNA gene from CM1 is 99 % similar to that of the Methanosarcina barkeri type strain MS (DSM 800) (Fig. 2) which was isolated from a sewage sludge digester [12, 13], and as such CM1 can be considered as a strain of M. barkeri
CM1 does not have the genes for gas vesicle biosynthesis that are found in the M. barkeri Fusaro genome [23], but it does have genes for the two-subunit acetylCoA synthetase (MCM1_1658 and 2708) that have been lost from the Fusaro strain
Summary
Ruminants are foregut fermenters and have evolved an efficient digestive system in which microbes ferment plant fibre and provide fermentation end-products and other nutrients for growth of the animal [1]. A variety of methanogens can be found in the rumen [2] and ruminant derived methane (CH4) accounts for about one quarter of all anthropogenic CH4 emissions [3], and is implicated as a driver of global climate change. CM1 grew as large cell aggregates in broth culture and showed the characteristic morphology associated with Methanosarcina barkeri [11] (Fig. 1). It was described as non-motile, and able to grow and produce methane from H2/CO2, acetate, methanol and methylamines. Characteristics of Methanosarcina barkeri CM1 are shown in Table 1 and Additional file 1
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