Copper as a controlling factor of anaerobic growth under N2O and biosynthesis of N2O reductase in denitrifying bacteria.

In order to determine the specific mineral requirement for N2O-anaerobic growth of the denitrifying bacteria Alcaligenes sp. NGIB 11015 and Alcaligenes faecalis IAM 1015, investigations were done using dithizone-treated KNO3-free modified Giltay's medium (dithizone-treated medium). When grown aerobically, the bacteria exhibited equally good growth in the presence or absence of an appropriate amount of copper. Anaerobic growth under N2O was stimulated by the addition of a proper amount of copper in both denitrifying bacteria. Growth in the medium demetalated by various treatments showed that copper was specifically necessary for the maximum growth under N2O. The optimum concentration of copper was between 0.5 to 1 μm and 20 to 40 μm for the anaerobic growth rate under N2O. Copper was indispensable for the biosynthesis of N2O reductase and is very likely to be a functional part of N2O reductase in denitrifying bacteria.