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Higher order taxa
Domain-Archaea; Phylum-Euryarchaeota; Class-Methanobacteria; Order-Methanobacteriales; Family-Methanobateriacea.
Description and significance
a. Most species (6 out of 7) of Methanobrevibacter can be isolated from gastrointestinal ecosystems (Lin, Miller 2007). Methanobrevibacter gottschalkii is one of those species. M. gottschalkii was named after Gerhard Gottschalk because of his understanding of the biochemistry concerning methanogens (Wikivusually). M. gottschalkii was first isolated and characterized by Terry Miller in 1986 (Lin, Miller 2007).
b. M. gottschalkii is coccobacillus with rounded ends (Lin, Miller 2007)). It is about 0.7 micrometers in width and 0.9micrometers in length and they occur either in pairs or short chains (Lin, Miller 2007). M. gottschalkii is Gram positive, and the cell wall is composed of pseudomurein (Lin, Miller 2007). M. gottschalkii cells are resistant to lysis by SDS (Lin, Miller 2007). It's optimum temperature is 37C, and it's optimum pH is 7 (1). M. gottschalkii is a strict anaerobe (Lin, Miller 2007). It can grow and produce methane form H2 and CO2, but not from formate, acetate, methanol, trimethylamines or methanol with H2 (Lin, Miller 2007).
Genome and genetics
a. The major branch of prokaryotes that M. gottschalkii belongs to is archaea (Pacheco 2016). Two similar species are Methanobrevibacter thaueri and Methanobrevibacter millerae SM9 (Pacheco 2016).
b. In order to study M. gottschalkii, the 16S rRNA genes are first amplified via PCR, and then cloned using E. coli plasmids so that the different gene variants can be separated (Janssen 2008). However, this is not the only method for studying M. gottschalkii (Janssen 2008). RNA-targeted DNA probes have also been used in order to analyze the archaeal community of rumen against the extracted RNA (Janssen 2008). Temporal temperature gradient gel electrophoresis is also used to separate 16S rRNA genes that have been amplified by PCR (Janssen 2008).
c. The genome of M. gottschalkii has not yet been sequenced, however, there is a genome sequence for the closely related M. millerae SM9 on Biomed Central (standardsingenomics.biomedcentral.com) (Pacheco 2016). The genome of M. millerae SM9 is made up of 2,543,538 bp in a circular chromosome, and it has an average G+C content of 31.8% (Pacheco 2016). M. ruminantium (another strain closely related to M. gottschalkii), has also been sequenced, and the similarity between the two suggests that any strategies based on the M. millerae SM9 genome should be applicable to any methanobrevibacter in the M. gottschalkii clade (Pacheco 2016).
Nutrition and metabolism
a. M. gottschalkii is a strict anaerobe, and the cells grown in rumen fluid medium are catalase negative (Lin, Miller 2008). M. gottschalkii grows and produces methane from H2 and CO2 (Lin, Miller 2008). It requires acetate and/or one or more components of trypticase or yeast extract for growth (Lin, Miller 2008). However, M. gottschalkii does not require coenzyme M or branched-chain fatty acids for growth (Lin, Miller 2008).
b. In a lab, M. gottschalkii can be grown in ATCC Medium 1892: Methanobacterium Medium (DSM 119), and the atmosphere needs to be 80% H2 and 20% CO2 (ATCC). M. gottschalkii can also grow in medium with salt concentrations similar to that of sea water, and the optimum pH for growth is 7 (ATCC).
c. The only major by-product made by M. gottschalkii is methane.
Ecology / Pathology
Ecology: M. gottschalkii plays a very important role in rumen function and animal nutrition. In a normally functioning rumen, proteins and polymeric carbohydrates are fermented by a mixed microbial community to volatile fatty acids (VFAs), which are: NH4+, CO2, and H2 (Janssen 2008). The methanogens in the rumen then metabolize the hydrogen (Janssen 2008). Efficient hydrogen removal by the methanogens leads to a nutritionally more favorable pattern of VFA formation, and it also leads to an increased rate of fermentation because it eliminates the inhibitory effect of H2 on the microbial fermentation (Janssen 2008). So M. gottschalkii has a positive effect on the overall environment that it lives in. As long as it metabolizes H2, it promotes more nutritionally favorable conditions (Janssen 2008).
Pathology: M. gottschalkii is not known for causing disease in the host in which it lives.
One recent study conducted in 2015 by Matthew McCabe focuses on the increase of M. gottschalkii in feed restricted cattle (McCabe, et al. 2015). Feed restriction in cattle production is used every now and then to reduce feed costs. After restriction, when normal feed levels are resumed, the cattle catch up to a normal weight through compensatory growth (McCabe, et al. 2015). DNA that was extracted from the rumen contents of 55 bulls showed that the restriction of feed for 125 days resulted in a large increase in the relative abundance of the M. gottschalkii clade, and a large reduction of a Succinivibrionacea clade (McCabe, et al. 2015). Mainly, the study was focused on the reduced acetate:propionate ratios in the rumen because they are associated with increased feed efficiency and reduced production of methane, which effects global warming (McCabe, et al. 2015).
Another study was done in 2015 on the methanogen communities in the gastrointestinal tract (GIT) of herbivores (St. Pierre, et al. 2015). In herbivores, enteric methane is produced from the digestion of plant biomass by mutualistic GIT microbial communities (St. Pierre, et al. 2015). Methane is a greenhouse gas that is released from the host into the environment, where it contributes to climate change (St. Pierre, et al. 2015). Since methane is produced by methanogenic archaea, the aim of this study was to find a way to facilitate the development of efficient mitigation strategies for livestock species, in order to reduce greenhouse gas (St. Pierre, et al. 2015).
(1) Lin, C. & Miller, T.L. (2002). Description of Methanobrevibacter gottschalkii sp. nov., Methanobrevibacter thaueri sp., nov., Methanobrevibacter woesei sp., nov., and Methanobrevibacter wolinii sp., nov. International Journal of Systematic and Evolutionary Microbiology, 52, 819-822.
(2) Methanobrevibater gottschalkii, Wikivisually, http://wikivisually.com/wiki/Methanobrevibacter_gottschalkii
(3) Kelly, W. Pacheco, D. Li, D. (2016). The complete genome sequence of the rumen methanogen Methanobrevibacter millerae SM9. Standards in Genomic Science. https://standardsingenomics.biomedcentral.com/articles/10.1186/s40793-016-0171-9
(4) Janssen, P. Kirs, M. (2008) Structure of the Archaeal Community of the Rumen. Applied Environmental Microbiology. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2446570/
(5) Methanobrevibacter gottschalkii (ATCC® BAA-1169™). ATCC. https://www.atcc.org/products/all/BAA-1169.aspx#culturemethod.
(6) McCabe M, Cormican, P. Kecogh, K. (2015). Illumina MiSeq Phylogenetic Amplicon Sequencing Shows a Large Reduction of an Uncharacterised Succinivibrionaceae and an Increase of the Methanobrevibacter gottschalkii Clade in Feed Restricted Cattle. Plos One. http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0133234
(7) St-Pierre, B. Cersosimo, L. Ishaq, S. Wright, A.D. (2015). Toward the identification of methanogenic archaeal groups as targets of methane mitigation in livestock animals. Frontiers in Microbiology. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4519756/