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Novel yellow, obligately methylotrophic and restricted facultatively methylotrophic bacteria, respectively designated strains ShipT and MimT, with the ribulose monophosphate pathway of C1 assimilation are described. Cells were strictly aerobic, Gram-negative, asporogenous, non-motile rods that multiply by binary fission, were mesophilic and neutrophilic and synthesized indole-3-acetic acid and exopolysaccharide. The predominant cellular fatty acids were C16 : 0 and C16 : 1. The major ubiquinone was Q-8. The predominant phospholipids were phosphatidylethanolamine and phosphatidylglycerol; diphosphatidylglycerol was absent. The two strains lacked α-ketoglutarate dehydrogenase and glutamate dehydrogenase. They assimilated ammonium via the glutamate cycle enzymes glutamine synthetase and glutamate synthase. The DNA G+C contents of strains ShipT and MimT were 50.7 and 54.5 mol% (T m), respectively. The level of 16S rRNA gene sequence similarity between these strains was very high (99.8 %) but they shared a low level of DNA–DNA relatedness (44 %). Based on 16S rRNA gene sequence analysis and low levels of DNA–DNA relatedness with the type strains of recognized species of the genus Methylophilus (31–36 %), strains ShipT and MimT are considered to represent novel species of the genus Methylophilus, for which the names Methylophilus flavus sp. nov. (type strain ShipT =DSM 23073T =VKM B-2547T =CCUG 58411T) and Methylophilus luteus sp. nov. (type strain MimT =DSM 22949T =VKM B-2548T =CCUG 58412T) are proposed.