Construction of an L-Arginine-Producing Mutant in Serratia marcescens

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Abstract
L-Arglnine biosynthesis in Serratia marcescens Sr41 was found to be controlled by (a) feedback inhibition of N-acetylglutamate synthetase and (b) repression of some L-arglnine biosynthetic enzymes, and an L-arginine-degrading system was found to exist. Accordingly, an L-arginine-producing mutant (aru argR argA) of S. marcescens Sr41 was constructed as follows. A mutant incapable of L-arginine utilization (aru) was obtained from the wild strain. Subsequently, from the lysine auxotroph (lysA) of aru mutant, a mutant having derepressed Larginine biosynthetic enzymes (argR) was isolated by screening for colonies that could utilize Na-acetyl-L-lysine in the presence of L-arginine. This selection was based on the finding that acetylornithinase of S. marcescens hydrolyzed Na-acetyl-L-lysine. On the other hand, to obtain a mutant with feedback-resistant N-acetylglutamate synthetase (argA), the proAB argD argR triple mutant was isolated from the indirectly suppressed revertant (proAB argD) of the proline auxotroph (proAB). Next, the argA mutant was isolated from the triple mutant by selection for resistance to 3,4-dehydro-DL-proline in the presence of L-arginirle. The argA mutation was introduced into the aru lysA argR strain by PS20-mediated cotransduction with lysA+. The aru argR argA lysA+ transductant produced 25 mg/ml of L-arglnine in the medium.