title: Simultaneous deficiency of both MurA and p60 proteins generates a rough phenotype in Listeria monocytogenes.
abstract: We examined eight spontaneously occurring rough mutants of Listeria monocytogenes for their ability to express two previously reported autolysins, p60 and MurA. All mutants lack MurA expression and show strongly reduced levels of extracellular p60. One rough strain harbors a variant of the p60 protein with a partially truncated catalytic domain. In seven cases there were shifts in the localization of p60 to the membrane fraction. Mutations within the secA2 gene, encoding an auxiliary protein secretion system paralog, were previously shown to be involved in the smooth-rough phenotypic variation seen with Listeria strains. An isogenic DeltasecA2 EGDe deletion strain displays a strong pleiotropic reduction of p60 and MurA, in addition to a large number of secreted and surface proteins. However, we observed no apparent SecA2 dysfunction in several of the investigated strains as determined by direct sequencing of the secA2 gene and complementation of the DeltasecA2 mutant with the respective allele cloned from the rough mutant. To determine the gene products required for the smooth-rough transition, we created mutants lacking the individual iap and murA genes as well as a Deltaiap DeltamurA double mutant. The double mutant displays a rough phenotype and exhibits many of the properties seen with the DeltasecA2 mutant. Our results implicate p60 and MurA as important determinants in controlling the cell shape of L. monocytogenes. We also identified homologous MurA and SecA2 proteins in other Listeria species. The muramidase in two species, L. innocua and L. welshimeri, shows activity similar to that of the MurA protein in L. monocytogenes.
authors.affiliation: Institut für Medizinische Mikrobiologie, Justus-Liebig-Universität, Frankfurter Strasse 107, D-35392 Giessen, Germany.
authors.forename: Silke
authors.initials: S
authors.lastname: Machata
authors.forename: Torsten
authors.initials: T
authors.lastname: Hain
authors.forename: Manfred
authors.initials: M
authors.lastname: Rohde
authors.forename: Trinad
authors.initials: T
authors.lastname: Chakraborty
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics; D001426:Bacterial Proteins / Q000032:analysis / Q000235:genetics* / Q000502:physiology; D015153:Blotting, Western; D018389:Codon, Nonsense; D004269:DNA, Bacterial / Q000737:chemistry; D017353:Gene Deletion; D005816:Genetic Complementation Test; D008074:Lipoproteins / Q000032:analysis / Q000235:genetics* / Q000502:physiology; D008089:Listeria monocytogenes / Q000166:cytology / Q000235:genetics* / Q000648:ultrastructure; D026901:Membrane Transport Proteins / Q000235:genetics; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D009024:Morphogenesis / Q000235:genetics; D009113:Muramidase / Q000032:analysis / Q000235:genetics* / Q000502:physiology; D009238:N-Acetylmuramoyl-L-alanine Amidase / Q000032:analysis / Q000235:genetics* / Q000502:physiology; D010641:Phenotype; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion
chemical_list: D001426:Bacterial Proteins; D018389:Codon, Nonsense; D004269:DNA, Bacterial; D008074:Lipoproteins; D026901:Membrane Transport Proteins; C116063:P60 protein, bacteria; D000069816:SEC Translocation Channels; D009113:Muramidase; D009238:N-Acetylmuramoyl-L-alanine Amidase; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins