Pleiotropic mutations in Serratia marcescens which increase the synthesis of certain exocellular proteins and the rate of spontaneous prophage induction |
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Authors: | U Winkler and K Timmis |
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Institution: | (1) Lehrstuhl für Biologie der Mikroorganismen, Ruhr-Universität Bochum, Bochum, Gerrmany;(2) Department of Medicine, Stanford University Medical Center, 94305 Stanford, California, U.S.A. |
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Abstract: | Summary Mutants of S. marcescens HY have been isolated which produce between five and one hundred times more exocellular nuclease than does the parental strain. These nuclease-superactive (nuc
su) mutants are highly pleiotropic: they produce more exocellular marcescin A and lipase than the wild-type and their ability to inactivate penicillin G is increased. Furthermore, all nuclease-superactive mutants if lysogenic for the heteroimmune phages Kappa and/or y show spontaneous induction rates for both prophages 10 to 200 fold greater than the corresponding wild-type. Nuc
su mutants of independent origin synthesize nuclease and marcescin A in approximately proportional amounts although the corresponding structural genes do not seem to be part of a single operon because some bacteriocin-superactive mutants were isolated which showed an increase of the synthesis of marcescin A only. Nuclease-defective (nuc) mutants are all of the non-pleiotropic type. Three hypotheses to explain the effects of the nuc
su mutation at the molecular level are discussed and some evidence in support of one of these hypotheses (gene-dosage effect) is presented in an accompanying paper (Timmis and Winkler, 1973). |
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