nitrobacter hamburgensis nitrobacter hamburgensis nitrobacter hamburgensis is a gram-negative bacterium from the genus of nitrobacter. nitrobacter hamburgensis scientific classification domain: bacteria phylum: pseudomonadota class: alphaproteobacteria order: hyphomicrobiales family: nitrobacteraceae genus: nitrobacter species: n. hamburgensis binomial name nitrobacter hamburgensisbock et al. 2001