phaeobacterium phaeobacterium phaeobacterium is a gram-negative, rod-shaped, phototrophic and motile genus of bacteria from the family of chromatiaceae with one known species (phaeobacterium nitratireducens). phaeobacterium scientific classification domain: bacteria phylum: pseudomonadota class: gammaproteobacteria order: chromatiales family: chromatiaceae genus: phaeobacteriumnupur et al. 2015 type species phaeobacterium nitratireducens species p. nitratireducens