ABSTRACT
Over time it became conventional to assign the methanotrophs to two separate taxonomic groups dubbed types I and II (Table 1). Type I belong to the γ subdivision of the Proteobacteria, while those of type II are in the α subdivision of the Proteobacteria. The type I genera are Methylobacter, Methylomicrobium, Methylomonas, Methylocaldum, Methylosphaera, Methylothermus, Methylosarcina, Methylohalobius, Methylosoma and Methylococcus, assigned to the family Methylococcaceae. Type I make use of the ribulose pathway in converting formaldehyde into multicarbon components that form part of cell biomass. The type II genera are Methylocystis, Methylosinus, Methylocella and Methylocapsa, all included among the Methylocystaceae. Type II bacteria utilise the serine pathway to convert formaldehyde into multicarbon compounds that again form part of the cell biomass.
