Description:
<jats:p>DNA sequence analysis of the human gut revealed the presence a seventh order of methanogens referred to as Methanomassiliicoccales.<jats:italic>Methanomassiliicoccus luminyensis</jats:italic>is the only member of this order that grows in pure culture. Here, we show that the organism has a doubling time of 1.8 d with methanol + H<jats:sub>2</jats:sub>and a growth yield of 2.4 g dry weight/mol CH<jats:sub>4</jats:sub>.<jats:italic>M. luminyensis</jats:italic>also uses methylamines + H<jats:sub>2</jats:sub>(monomethylamine, dimethylamine, and trimethylamine) with doubling times of 2.1–2.3 d. Similar cell yields were obtained with equimolar concentrations of methanol and methylamines with respect to their methyl group contents. The transcript levels of genes encoding proteins involved in substrate utilization indicated increased amounts of mRNA from the<jats:italic>mtaBC2</jats:italic>gene cluster in methanol-grown cells. When methylamines were used as substrates, mRNA of the<jats:italic>mtb/mtt</jats:italic>operon and of the<jats:italic>mtmBC1</jats:italic>cluster were found in high abundance. The transcript level of<jats:italic>mtaC2</jats:italic>was almost identical in methanol- and methylamine-grown cells, indicating that genes for methanol utilization were constitutively expressed in high amounts. The same observation was made with resting cells where methanol always yielded the highest CH<jats:sub>4</jats:sub>production rate independently from the growth substrate. Hence,<jats:italic>M. luminyensis</jats:italic>is adapted to habitats that provide methanol + H<jats:sub>2</jats:sub>as substrates.</jats:p>