hydrogenophaga caeni hydrogenophaga caeni hydrogenophaga caeni is a gram-negative, anaerobic, catalase- and oxidase-positive, motile bacterium from the comamonadaceae family, with a single polar flagellum, which was isolated from an activated sludge. colonies of h. caeni are white colored. hydrogenophaga caeni scientific classification domain: bacteria phylum: pseudomonadota class: betaproteobacteria order: burkholderiales family: comamonadaceae genus: hydrogenophaga species: h. caeni binomial name hydrogenophaga caenichung et al. 2007, sp. nov. type strain dsm 17962, emb71, kctc 12613