6) and Methanoregula boonei 6A8 (Score 480, Genome Id 456442.10) were the closest relatives of Methanoculleus sp. MH98A. Digital DNA–DNA hybridization, performed as described by Auch et al. (2010), revealed only 54.2 ± 2.7% similarity between MH98A

and M. marisnigri JR1 indicating distinct delineation between the two species. M. boonei 6A8 was found to be an even more distant relative of MH98A with a genome to genome similarity of only 16.8 ± 2.2%. Further analysis revealed that the draft genome of strain MH98A was 2,542,436 bp in size with 2317 coding sequences, 1 copy of 5S, 16S and 23S rRNA genes and 50 tRNA genes. 32% of the predicted coding sequences were assigned to subsystem categories. The MH98A genome sequence analysis revealed 22 unique genes associated with subsystems when compared to its closest phylogenetic relative, M. marisnigri JR1. Among these are genes associated with carbohydrate metabolism, cell wall component synthesis high throughput screening and capsule ( Leahy et al., 2010 and Poli et al., 2011), cofactor synthesis, vitamin synthesis, prosthetic group synthesis, pigment synthesis, DNA metabolism, membrane transport, protein metabolism and potassium metabolism. A unique gene associated with subsystem of cofactor synthesis, namely the gene encoding coenzyme gamma-F420-2:l-glutamate ligase was detected. Coenzyme F420 is essential for methane synthesis

via the hydrogenotrophic selleck chemicals pathway from carbon dioxide and hydrogen. Formate dehydrogenase, a key enzyme for formate utilization in the methanogenesis pathway, was also detected. These observations were consistent with the substrate utilization profile of MH98A which consumes H2/CO2 and formate as substrates for methane production. Genes coding for different enzymes

in hydrogenotrophic methanogenesis which include, formylmethanofuran dehydrogenase, formylmethanofuran–tetrahydromethanopterin N-formyltransferase, N5, N10-methenyltetrahydromethanopterin cyclohydrolase, F420-dependent methylenetetrahydromethanopterin dehydrogenase, F420-dependent below N5, N10-methylenetetrahydromethanopterin reductase, N5-methyltetrahydromethanopterin: coenzyme M methyltransferase and Methyl coenzyme M reductase were detected. Further comparative genome analyses are ongoing to better elucidate the methanogenesis pathway in Methanoculleus sp. MH98A and improve understanding of the evolutionary relationship between Methanoculleus strains associated with submarine sediments from distant geographical locations. The draft genome sequence of Methanoculleus sp. MH98A was deposited in the DDBJ/EMBL/GenBank database under the Accession number JMIO00000000.1. The strain Methanoculleus sp. MH98A is available from Dr. P.K. Dhakephalkar (Agharkar Research Institute, G.G. Agarkar Road, Pune 411004. India). The strain is also available at MACS Collection of microorganism (Registration No. WDCM 561) under the Accession No. MCMB-889.