methanothermococcus methanothermococcus in taxonomy, methanothermococcus is a genus of the methanococcaceae. the cells are shaped like irregular bars and tend to be gram-negative. they are mobile via polar flagella. they require acetate to grow. methanothermococcus scientific classification domain: archaea kingdom: euryarchaeota phylum: euryarchaeota class: methanococci order: methanococcales family: methanococcaceae genus: methanothermococcus binomial name methanothermococcuswhitman 2002 species m. okinawensis m. thermolithotrophicus