Role of nitrogen sources and metal ions in urease synthesis byMicrococcus varians.

Urease (urea amidohydrolase E.C.3.5.1.5) synthesis inMicrococcus varians U-9 was not affected by nitrogen source (peptone or glutamic acid) or its concentration: but depended on the ratio of peptone and urea in culture medium. WhenM. varians grew in culture medium with peptone at or above 0.48g/l and NH4Cl as an additional nitrogen source, two maxima of urease synthesis occurred; one in the exponential growth phase and the second in the stationary growth phase. Though this bacterium could not utilize either urea or ammonia as the sole nitrogen source, urea caused only one maximum of urease synthesis to occur and shifted the maximum into late exponential phase, suggesting that urea acts as a regulatory factor in urease synthesis. Synthesis of urease was not induced either by urea or by nitrogen starvation and was not repressed by ammonia or by excess of complex nitrogen source. NI(2+) (up to 0.1 mM) stimulated urease synthesis but decreased bacterial growth, while Co(2+) only affected bacterial growth and at 0.1 mM Inhibited the growth.