title: Emergence of phenotypic variants upon mismatch repair disruption in Pseudomonas aeruginosa.
abstract: MutS is part of the bacterial mismatch repair system that corrects point mutations and small insertions/deletions that fail to be proof-read by DNA polymerase activity. In this work it is shown that the disruption of the P. aeruginosa mutS gene generates the emergence of diverse colony morphologies in contrast with its parental wild-type strain that displayed monomorphic colonies. Interestingly, two of the mutS morphotypes emerged at a high frequency and in a reproducible way and were selected for subsequent characterization. One of them displayed a nearly wild-type morphology while the other notably showed, compared with the wild-type strain, increased production of pyocyanin and pyoverdin, lower excretion of LasB protease and novel motility characteristics, mainly related to swarming. Furthermore, it was reproducibly observed that, after prolonged incubation in liquid culture, the pigmented variant consistently emerged from the mutS wild-type-like variant displaying a reproducible event. It is also shown that these P. aeruginosa mutS morphotypes not only displayed an increase in the frequency of antibiotic-resistant mutants, as described for clinical P. aeruginosa mutator isolates, but also generated mutants whose antibiotic-resistant levels were higher than those measured from spontaneous resistant mutants derived from wild-type cells. It was also found that both morphotypes showed a decreased cytotoxic capacity compared to the wild-type strain, leading to the emergence of invasive variants. By using mutated versions of a tetracycline resistance gene, the mutS mutant showed a 70-fold increase in the reversion frequency of a +1 frameshift mutation with respect to its parental wild-type strain, allowing the suggestion that the phenotypical diversity generated in the mutS population could be produced in part by frameshift mutations. Finally, since morphotypical diversification has also been described in clinical isolates, the possibility that this mutS diversification was related to the high frequency hypermutability observed in P. aeruginosa CF isolates is discussed.
authors.affiliation: Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba, Argentina.
authors.forename: Andrea M
authors.initials: AM
authors.lastname: Smania
authors.affiliation: Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba, Argentina.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Segura
authors.affiliation: Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba, Argentina.
authors.forename: Roberto J
authors.initials: RJ
authors.lastname: Pezza
authors.affiliation: Departamento de Farmacia, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, Argentina.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Becerra
authors.affiliation: Departamento de Farmacia, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, Argentina.
authors.forename: Inés
authors.initials: I
authors.lastname: Albesa
authors.affiliation: Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba, Argentina.
authors.forename: Carlos E
authors.initials: CE
authors.lastname: Argaraña
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics*; D002460:Cell Line; D003470:Culture Media; D004268:DNA-Binding Proteins / Q000235:genetics*; D004285:Dogs; D024881:Drug Resistance, Bacterial; D004847:Epithelial Cells / Q000382:microbiology; D016368:Frameshift Mutation; D051719:MutS DNA Mismatch-Binding Protein; D009154:Mutation; D010641:Phenotype; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D037521:Virulence Factors
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D003470:Culture Media; D004268:DNA-Binding Proteins; D037521:Virulence Factors; D000251:Adenosine Triphosphatases; D051719:MutS DNA Mismatch-Binding Protein