Characteristics of nitrogen transformation and intracellular nitrite accumulation by the hypothermia bacterium Arthrobacter arilaitensis

[Display omitted] •Intracellular nitrite nitrogen accumulation was discovered in cells.•Stepwise inhibition revealed the nitrogen removal pathway.•The enzyme activity of AMO was as high as 0.42 U/mg protein.•Extracellular nitrite accumulated with nitrate but not with ammonium.•Intracellular nitrite accumulation occurs regardless of nitrogen source. A new nitrite accumulation pathway was discovered in the nitrogen conversion process of Arthrobacter arilaitensis. The extracellular nitrite reached 0.65 and 43.66 mg/L with hydroxylamine and nitrate as the sole nitrogen source, respectively. The enzyme activities of ammonia monooxygenase, hydroxylamine oxidoreductase and nitrate reductase were 0.42, 0.0014 and 0.0049 U/mg protein, respectively. The activity of nitrite reductase was completely inhibited by diethyldithiocarbamate. Intriguingly, the intracellular nitrite accumulated as high as 43.0, 42.26, 39.94 and 35.01 mg/L, when the Arthrobacter arilaitensis was incubated with Luria-Bertani medium, ammonium, nitrate and nitrite as the nitrogen source, respectively. These results confirmed that the highest concentration of intracellular nitrite was accumulated when LB was selected as the nitrogen source, followed by ammonium and nitrate, then nitrite was the least. To date, biochemical mechanism responsible for the accumulation of a high concentration of intracellular nitrite is unknown.