Strain RMAST has: (i) the highest temperature for growth (80 uC): M. thermautotrophicus DHT has the next highest in the genus (75 uC); (ii) a requirement of organic factors
(either Casamino acids, tryptone, yeast extract or vitamins) for growth: no other member of the genus Methanothermobacter requires required these factors; and (iii) the lowest G+C content (41.5 mol%): Methanothermobacter thermophilus MT has the next lowest (44.7 mol%) (Table 1).