Image source: http://www.bact.wisc.edu/Bact303/Methanococcus.jpeg
Archaea; Euryarchaeota; Methanococci; Methanococcales; Methanococcaceae; Methanococcus; Methanococcus maripaludis
Chromosome: 1,661,137 bp
Methanococcus maripaludis (Latin "mare" meaning sea, "palus" meaning marsh) is a model species among the methanogenic Archaea. Originally characterized by W. J. Jones, the species was the predominent methanogen isolated from a salt-marsh sediment in South Carolina, United States. Numerous additional isolates were obtained by W. Whitman, including strain S2, also known as strain LL. M. maripaludis is strictly anaerobic, hydrogenotrophic (growing on hydrogen and carbon dioxide) and nitrogen-fixing, and is a mesophilic relative of the hyperthermophilic Methanococcus jannaschii. Cells are irregular cocci with weak motility. M. maripaludis is an excellent laboratory model because of rapid, reliable growth, a complete genome sequence, a robust set of genetic tools, and ongoing studies with expression arrays and proteomics.
Methanococcus maripaludis possesses a small, circular genome of 1.66 Mb in length with no extrachromosomal elements. The genome has a low, 33%, GC content. Open reading frame predictions indicate 1719 orfs. The maripaludis genome is relatively simple with few repeated sequences, though it contains three copies of the 16S and 23S ribosomal genes. Interestingly, while the genome of the closely related Methanocaldococcus jannaschii contains a number of inteins, maripaludis appears to lack inteins entirely, even in orfs that are otherwise highly homologous to their M. jannashii counterparts.
University of Washington Genome Center.