title: Role of RpoS and MutS in phase variation of Pseudomonas sp. PCL1171.
abstract: Pseudomonas sp. strain PCL1171 undergoes reversible colony phase variation between opaque phase I and translucent phase II colonies, which is dependent on spontaneous mutations in the regulatory genes gacA and gacS. Mutation of the mutS gene and constitutive expression of rpoS increases the frequency at which gac mutants appear 1000- and 10-fold, respectively. Experiments were designed to study the relationship between gacS, rpoS and mutS. These studies showed that (i) a functional gac system is required for the expression of rpoS, (ii) RpoS suppresses the expression of mutS and therefore increases the frequency of gac mutants, and (iii) upon mutation of rpoS and gacS, the expression of mutS is increased. Mutation of gacS abolishes suppression of mutS expression in stationary growth, suggesting that additional gac-dependent factors are involved in this suppression. In conclusion, inefficient mutation repair via MutS, of which the expression is influenced by gacA/S itself and by rpoS in combination with other factors, contributes to the high frequency of mutations accumulating in gacA/S. The role of RpoS in the growth advantage of a gac mutant was analysed, and mutation of rpoS only reduced the length of the lag phase, but did not affect the growth rate, suggesting a role for both RpoS and a reduction of metabolic load in the growth advantage of a gac mutant.
authors.affiliation: Institute of Biology, Leiden University, Clusius Laboratory, Wassenaarseweg 64, 2333 AL Leiden, The Netherlands.
authors.forename: Daan
authors.initials: D
authors.lastname: van den Broek
authors.affiliation: Institute of Biology, Leiden University, Clusius Laboratory, Wassenaarseweg 64, 2333 AL Leiden, The Netherlands.
authors.forename: Thomas F C
authors.initials: TFC
authors.lastname: Chin-A-Woeng
authors.affiliation: Institute of Biology, Leiden University, Clusius Laboratory, Wassenaarseweg 64, 2333 AL Leiden, The Netherlands.
authors.forename: Guido V
authors.initials: GV
authors.lastname: Bloemberg
authors.affiliation: Institute of Biology, Leiden University, Clusius Laboratory, Wassenaarseweg 64, 2333 AL Leiden, The Netherlands.
authors.forename: Ben J J
authors.initials: BJJ
authors.lastname: Lugtenberg
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D051719:MutS DNA Mismatch-Binding Protein; D009154:Mutation; D011549:Pseudomonas / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C091100:GacA protein, Bacteria; D012808:Sigma Factor; D014157:Transcription Factors; C069567:sigma factor KatF protein, Bacteria; C074165:lemA protein, bacterial; D000251:Adenosine Triphosphatases; D051719:MutS DNA Mismatch-Binding Protein