Bacteria; Proteobacteria; Gammaproteobacteria; Xanthomonadales; Xanthomonadaceae; Rhodanobacter; denitrificans .
2APBS1 and 116-2 .
Rhodanobacter denitrificans is a yellow-pigmented, gram-negative, non-sporulating, motile,slow-growing, and facultatively anaerobic rod-shaped bacterium with the ability to perform complete denitrification . For Rhodanobacter species, denitrification was not a characteristic until the discovery of R. denitrificans . Denitrification is the conversion of nitrate to N2 through nitrite, nitric and nitrous oxide intermediates catalyzed by microbial enzymes . Only two species of Rhodanobacter, one of them being Rhodanobacter denitrificans, is capable of this process . In the absence of oxygen, growth is fueled by the use of nitrate, nitrite, and nitrous oxide as electron acceptors . Rhodanobacter denitrificans has a salt tolerance up to 2% NaCl . Growth was observed at pH 4-8 and 10-35ºC, optimally at pH 6.5 and 30ºC . The two strains of R. denitrificans, 2APBS1 and 116-2, were found at Oak Ridge Integrated Field Research Challenge (ORIFRC) . ORIFRC is a model nuclear legacy site with high levels of nitrate and acidity, with uranium and other heavy metal contaminants . At ORIFRC, 2APBS1 was isolated from Area 2 (pH 6-7 and nitrate level <2 mM) and 116-2 was isolated from Area 3 (pH 3-4 and nitrate level 10s to 100s mM) . The two strains are highly abundant and active in acidic, nitrate rich subsurface environments with high metal (e.g. uranium) concentrations . The characteristic of survival in these harsh environments allow R. denitrificans to conduct bioremediation of the contamination sites by denitrification .