Pseudomonas mesophilica Austin and Goodfellow 1979 Methylobacterium mesophilicum is a Gram-negative, soil-dwelling bacterium, reported to be an opportunistic pathogen in immunocomprimised patients.

Pink pigmentation is the primary diagnostic characteristic used in the initial isolation of Methylobacteria.

M. mesophilicum and M. zatmanii are the two most commonly reported species isolated in clinical samples.

[1][2] Methylobacteria have been reported to exhibit resistance to chlorination[3] and have been isolated from tap water in various clinical settings including: an investigation of a pseudo-outbreak,[4] water from dental units,[5] and blood purification units.

[citation needed] Tap water is a suspected mode of transmission.