nitrosomonas oligotropha nitrosomonas oligotropha nitrosomonas oligotropha is an ammonia-oxidizing, aerobe, gram-negative bacterium from the genus of nitrosomonas which occurs in chloraminated drinking water systems. nitrosomonas oligotropha scientific classification domain: bacteria phylum: pseudomonadota class: betaproteobacteria order: nitrosomonadales family: nitrosomonadaceae genus: nitrosomonas species: n. oligotropha binomial name nitrosomonas oligotrophakoops et al. 2001 type strain nm 45