Denitrification by Actinomycetes and Purification of Dissimilatory Nitrite Reductase and Azurin from Streptomyces thioluteus

ABSTRACT Many actinomycete strains are able to convert nitrate or nitrite to nitrous oxide (N 2 O). As a representative of actinomycete denitrification systems, the system of Streptomyces thioluteus was investigated in detail. S. thioluteus attained distinct cell growth upon anaerobic incubation with nitrate or nitrite with concomitant and stoichiometric conversion of nitrate or nitrite to N 2 O, suggesting that the denitrification acts as anaerobic respiration. Furthermore, a copper-containing, dissimilatory nitrite reductase (CuNir) and its physiological electron donor, azurin, were isolated. This is the first report to show that denitrification generally occurs among actinomycetes.