-
[show abstract]
[hide abstract]
ABSTRACT: The inactivation of the rpoS gene, which encodes the sigma S subunit of RNA polymerase of rhizospheric strain Pseudomonas chlororaphis 449 results in a drastic (5–8-fold) decrease in the synthesis of phenazine antibiotics, a decline in the acid and alkaline
phosphatase activities (pH 2.5 and 8.8, respectively), and the antagonistic activity of this strain against phytopathogenic
fungus Rhizoctonia solani. A mutation in the rpoS gene also causes a minor decrease of lipase and proteolytic activity in the supernatants of Pseudomonas chlororaphis 449 and has no substantial effect on the synthesis of three types of N-acyl homoserine lactones, the signal molecules of quarum sensing regulation, and the ability of bacteria to migrate over
the medium surface (swarming).
Molecular Genetics Microbiology and Virology 04/2012; 24(1):7-11. · 0.23 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The introduction into strain Pseudomonas chlororaphis 449 of plasmid pME6863 that contains the cloned gene for N-acyl-homoserine lactonase, AiiA, leads to the degradation of all three types of N-acylhomoserine lactones produced by this strain (N-butanoyl-homoserine lactone, N-hexanoyl-homoserine lactone, and N-3-oxo-hexanoyl-homoserine lactone). This causes a drastic reduction in the synthesis of phenazine pigment and decreases the
ability of cells to migrate on the surface of nutrient medium. However, the antagonistic activity of P. chlororaphis 449 toward phytopathogenic fungi Sclerotinia sclerotiorum and Rhizoctonia solani is not only decreased, but is even slightly increased; no essential changes in the exoprotease activity were observed. It
is assumed that one of the QS systems of P. chlororaphis 449 may exert the repression effect on the expression of genes, which determine the two latter cell activities.
Russian Journal of Genetics 04/2012; 45(1):30-34. · 0.43 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: 228 strains of soil and rhizosphere pseudomonads isolated in different geographic zones were screened, with the use of two
tester systems, for the capacity to produce N-acyl-homoserine lactones (AHLs), which are autoinducers involved in quorum-sensing (QS) regulation. AHL production was found
in 11.4% of the strains investigated. In five Pseudomonas chlororaphis strains shown to be active AHL producers and chosen for further study, PCR identified two QS systems that involved the phzI, phzR, csaI, and csaR genes; this finding suggests the conservative nature of these regulation systems in P. chloroaphis. Strain P. chlororaphis 449, chosen as a model object and studied in greater detail, produced three AHL species including N-butanoyl-homoserine lactone and N-hexanoyl-homoserine lactone. This strain produced three types of phenazine antibiotics, as well as siderophores and cyanide;
it also exhibited antagonistic properties toward a wide spectrum of phytopathogenic fungi. The phzI and csaI genes, coding for synthases of AHLs of two types, were cloned and sequenced; mutants with knocked-out phzI and csaI genes were obtained. With the use of transposon mutagenesis and the gene substitution method, mutations were obtained in
the global expression regulator genes gacS, coding for the GacA-GacS regulation system kinase, and rpoS, coding for the sigma S subunit of RNA polymerase. The effect of these mutations on the AHL synthesis and on the regulation
of various metabolic processes in P. chlororaphis was studied.
Microbiology 04/2012; 75(4):398-400. · 3.06 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: 228 strains of soil and rhizosphere pseudomonads isolated in different geographic zones were screened, with the use of two tester systems, for the capacity to produce N-acetyl-homoserine lactones (AHLs), which are autoinducers involved in quorum-sensing (QS) regulation. AHL production was found in 11.4% of the strains investigated. In five Pseudomonas chlororaphis strains shown to be active AHL producers and chosen for further study, PCR identified two QS systems that involved the phzI, phzR, csaI, and csaR genes; this finding suggests the conservative nature of these regulation systems in P. chlororaphis. Strain P. chlororaphis 449, chosen as a model object and studied in greater detail, produced three AHL species including N-butanoyl-homoserine lactone and N-hexanoyl-homoserine lactone. This strain produced three types of phenazine antibiotics, as well as siderophores and cyanide; it also exhibited antagonistic properties toward a wide spectrum of phytopathogenic fungi. The phzI and csaI genes, coding for synthases of AHLs of two types, were cloned and sequenced; mutants with knocked-out phzI and csal genes were obtained. With the use of transposon mutagenesis and the gene substitution method, mutations were obtained in the global expression regulator genes gacS, coding for the GacA-GacS regulation system kinase, and rpoS, coding for the sigma S subunit of RNA polymerase. The effect of these mutations on the AHL synthesis and on the regulation of various metabolic processes in P. chlororaphis was studied.
Mikrobiologiia 75(4):465-7.
