Note: Nitrosomonas eutropha C71 is now Nitrosomonas eutropha C91.

Nitrosomonas eutropha C91 (Kingdom: Bacteria) is an autotrophic nitrifying bacterium. As a member of the ammonia-oxidizing bacteria, it catalyzes the oxidation of ammonia to meet its energy requirements for growth. This reaction is the first step in the oxidation of ammonia to nitrate which is an integral part of the biogeochemical N cycle and plays a central role in the availability of nitrogen to plants and hence in limiting CO₂ fixation. Nitrifying bacteria also are important players in the treatment of industrial and sewage waste in the first step of oxidizing ammonia to nitrate. Evidence suggests that ammonia-oxidizing bacteria contribute significantly to the global production of nitrous oxide (produced by the reduction of nitrite).

Nitrosomonas eutropha C91 ( eu -, good; trophos , one who feeds) (also known as strain Nm57; formerly ATCC 25984, which is no longer available) is a Gram-negative betaproteobacterium closely related to the better studied Nitrosomonas europaea (Chain, 2001-2009). N.eutropha is an aerobic chemolithoautotroph deriving its carbon from CO₂ and generating energy and reducing equivalents from the oxidation of ammonia to nitrite. It is pleomorphic (rod to pear-shaped) and is occasionally found in short chains (Koops, 1991).   N. eutropha is commonly found in strongly eutrophic environments such as municipal and industrial sewage disposal systems and has a high tolerance for elevated ammonia concentrations. The cells are motile. The utilization of urea was not observed.   Although N. eutropha is very similar to N. europaea, some notable differences exist. N. eutropha is able to grow anaerobically with H₂ as the reductant and nitrite as the electron acceptor. However, the genomic sequence of N. europaea fails to give any indication supporting the presence of this ability.   Additionally, unlike N. europaea , N. eutropha possesses carboxysomes.   These differences suggest that significant differences in metabolic capability may exist between these related strains.

References:

Chain, P., J. Lamerdin, F. Larimer, W. Regala, V. Lao, M. Land, L. Hauser, A. Hooper, M. Klotz, J. Norton, L. Sayavedra-Soto, D. Arciero, N. Hommes, M. Whittaker, D. Arp. 2003. Complete genome sequence of the ammonia oxidizing bacterium and obligate chemolithoautotroph Nitrosomonas europaea .   J. Bacteriol.   185: 2759-2773.

Koops H-P, Böttcher B, Möller U, Pommerening-Röser A, Stehr G. Classification of eight new species of ammonia-oxidizing bacteria: Nitrosomonas communis sp. nov., Nitrosomonas ureae sp. nov., Nitrosomonas aestuarii sp. nov., Nitrosomonas marina sp. nov., Nitrosomonas nitrosa sp. nov., Nitrosomonas eutropha sp. nov., Nitrosomonas oligotropha sp. nov. J Gen Microbiol. 1991; 13 :1689-1699.