SprI/SprR Quorum Sensing System of 94.

In this study, we investigated the quorum sensing (QS) regulatory system of the psychrotrophic strain 94 isolated from spoiled refrigerated meat. The strain produced several -acyl--homoserine-lactone (AHL) QS signal molecules, with -(3-oxo-hexanoyl)--homoserine lactone and -(3-hydroxy-hexanoyl)--homoserine lactone as two main types. The and genes encoding an AHL synthase and a receptor regulatory protein, respectively, were cloned and sequenced.

Effect of inactivation of luxS gene on the properties of Serratia proteamaculans 94 strain.

The luxS gene is responsible for the synthesis of AI-2 (autoinducer-2), a signaling molecule that participates in quorum sensing regulation in a large number of bacteria. In this work, we investigated which phenotypes are regulated by luxS gene in Serratia proteamaculans 94, psychrotrophic strain isolated from spoiled refrigerated meat. AI-2 was identified in S.

The effect of mutation in the clpX gene on the synthesis of N-acyl-homoserine lactones and other properties of Burkholderia cenocepacia 370.

In order to study the regulation of N-acyl-homoserine lactones synthesis (AHLs, the signal molecules of Quorum Sensing regulation) in Burkholderia cenocepacia strain 370 we obtained mutants with increased AHL production. One of the mutants, named BC-B6, was obtained by TnMod-RKm(r) plasposon mutagenesis. The plasposon insertion was located within the clpX gene encoding the ATPase subunit ClpX of the ClpXP protease.

[The Effect of Introduction of the Heterologous Gene Encoding the N-acyl-homoserine Lactonase (aiiA) on the Properties of Burkholderia cenocepacia 370].

To study the role of Quorum Sensing (QS) regulation in the control of the cellular processes of Burkholderia cenocepacia 370, plasmid pME6863 was transferred into its cells. The plasmid contains a heterologous gene encoding for AiiA N-acyl-homoserine lactonase, which degrades the signaling molecules of the QS system of N-acyl-homoserine lactones (AHL). An absence or reduction of AHL in the culture was revealed with the biosensors Chromobacterium violaceum CV026 and Agrobacterium tumifaciens NT1/pZLR4, respectively.

Antibacterial effects of silver nanoparticles on gram-negative bacteria: influence on the growth and biofilms formation, mechanisms of action.

Antibacterial action of silver nanoparticles (AgNP) on Gram-negative bacteria (planctonic cells and biofilms) is reported in this study. AgNP of 8.3 nm in diameter stabilized by hydrolyzed casein peptides strongly inhibited biofilms formation of Escherichia coli AB1157, Pseudomonas aeruginosa PAO1 and Serratia proteamaculans 94 in concentrations of 4-5 μg/ml, 10 μg/ml and 10-20 μg/ml, respectively.

[Mutants of Burkholderia cenocepacia with a change in synthesis of N-acyl-homoserine lactones--signal molecules of Quorum Sensing regulation].

By means of plasposon mutagenesis, mutants of Burkholderia cenocepacia 370 with the change in production of N-acyl-homoserine lactones (AHL), signal molecules of the Quorum Sensing system of regulation, were obtained. To localize plasposon insertions in mutant strains, fragments of chromosomal DNA containing plasposons were cloned, adjacent DNA regions sequenced, and a search for homologous nucleotide sequences in the GeneBank was initiated. It has been shown that the insertion of plasposon into gene lon encoding lon proteinase drastically decreases AHL synthesis.

GacS-dependent regulation of enzymic and antifungal activities and synthesis of N-acylhomoserine lactones in rhizospheric strain Pseudomonas chlororaphis 449.

Pseudomonas chlororaphis strain 449 isolated from the rhizosphere of maize suppresses numerous plant pathogens in vitro. The strain produces phenazine antibiotics and synthesizes at least three types of quorum sensing signaling molecules, N-acylhomoserine lactones. Here we have shown that the rhizospheric P.

[Structure and expression of gene vfr in Pseudomonas chlororaphis 449].

Gene vfr previously described only in Pseudomonas aeruginosa was cloned, identified, and sequenced in cells of Pseudomonas chlororaphis 449; its localization in the chromosome was determined. Amino acid sequence of the protein encoded by gene vfr in P. chlororaphis 449 was shown to have a 83% identity with the Vfr protein of P.

[Synthesis of N-acyl-homoserine lactones, phenazines, some enzymatic activities and antifungal activity of Pseudomonas chlororaphis 449 cells carrying an inactivated rpoS gene].

Inactivation of the rpoS gene encoding for sigma S subunit of RNA polymerase of the rhizospheric strain Pseudomonas chlororaphis 449 results in a sharp decrease (5-8 fold) of phenazine antibiotics synthesis, decline of acid and alkaline phosphatases (pH 2.5 and 8.8, respectively) activities and antagonistic activity of this strain against phytopathogenic fungus Rhizoctonia solani.

[Expression of N-acyl-homoserine lactonase AiiA gene affects properties of rhizospheric strain Pseudomonas chlororaphis 449].

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-acyl-homoserine lactones produced by this strain (N-butanoyl-L-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.

[Quorum sensing systems of regulation, synthesis of phenazine antibiotics, and antifungal (corrected) activity in rhizospheric bacterium Pseudomonas chlororaphis 449].

Strain Pseudomonas chlororaphis 449, an antagonist of a broad spectrum of phytopathogenic microorganisms isolated from the maize rhizosphere, was shown to produce three phenazine antibiotics: phenazine-1-carboxylic acid (PCA), 2-hydroxylphenazine-1-carboxylic acid (2-OH-PCA), and 2-hydroxylphenazine (2-OH-PHZ). Two Quorum Sensing (QS) systems of regulation were identified: PhzIR and CsaI/R. Genes phzI and csaI were cloned and sequenced.

[Influence of mutations in global regulator genes grrS and rpoS on synthesis of phosphatases in Serratia plymuthica].

The participation of global regulators GrrS (sensor kinase GacA/GacS-like regulatory system) and sigma S subunit of RNA polymerase in the control of phosphatase synthesis in a soil bacterium Serratia plymuthica was shown. In cells of null mutants for genes grrS and rpoS synthesis of low-acidic and alkaline phosphatases was markedly decreased.

Phytase activity and its regulation in a rhizospheric strain of Serratia plymuthica.

Serratia plymuthica strain IC1270 isolated from the rhizosphere, possessing antagonistic activity towards a wide range of plant-pathogenic fungi, is able to hydrolyze phytate. Phytase activity was found intracellularly, while no activity was detected in the culture liquid. Optimum activity was found at pH 4-5; it completely disappeared at pH > 7.

[Quorum-sensing regulation in soil pseudomonads].

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.

Activity of Serratia plymuthica IC1270 gene chiA promoter region in Escherichia coli mutants deficient in global regulators of transcription.

To study the regulation of expression of the Serratia plymuthica gene chiA encoding a 58-kDa endochitinase, its 586-bp-long upstream regulatory region was cloned, sequenced and fused to a promoterless lac operon in phage lambdaRS45 to obtain a single-copy transcriptional fusion (P F1chiA )-lac in lysogens of Escherichia coli wild-type strains or their mutants deficient in various global regulators of transcription. The level of P F1chiA -lac expression increased about 20- and 90-fold, respectively, in E. coli K12 Deltahns and double Deltahns stpA mutants deficient in H-NS, and in both H-NS and StpA DNA-binding histone-like proteins, as compared to levels in the wild-type strain.

[Activation of the expression of the microcin C51 operon upon glucose starvation of cells at the exponential growth phase].

It was earlier shown that expression of the microcin C51 operon in Escherichia coli cells is activated upon decelerated growth of cells during their transition to the stationary growth phase and depends on the sigmaS subunit of RNA polymerase. Using a single-copy construct containing the cloned promoter region of the microcin C51 operon and a promoterless lac operon (P(mcc)-lac), it was shown that the promoter of the microcin operon was also induced by stress caused by the transition of cells at the exponential growth phase into the medium without glucose as a sole carbon source. Activation of P(mcc)-lac expression upon severe glucose starvation occurred in rpoS+ and rpoS- strains.

Production of N-acylhomoserine lactone signal molecules by gram-negative soil-borne and plant-associated bacteria.

Quorum-sensing control mediated by N-acylhomoserine lactone (AHL) signal molecules has been established as a key feature in the regulation of various metabolic traits in many bacteria. Approximately 300 strains representing 6 genera and 18 species of soil-borne and plant-associated Gram-negative bacteria isolated in various regions of the former USSR using two reporter systems were screened for AHL production. The production was observed in 17.

[Phytase activity in some groups of bacteria. Search for and cloning of genes for bacterial phytases].

A search for phytase genes in 9 Bacillus strains from the collection of IMGAN was implemented. The growth optimum of strains IX-22, IX-12B, K17-2, K18, IMG I, IMG II, M4 and M8 was 50-60 degrees C; the optimal growth temperature for Bacillus sp. 790 was 45-47 degrees C.

[Clinical strains of Burkholderia cepacia: characteristic and detection of the components in the quorum sensing regulatory system].

Described in the paper are characteristics of B. cepacia clinical strains isolated from patients at Moscow hospitals. The strains were investigated for the presence of proteolytic, chitinolytic, hemolytic and lipase activities as well as for presence of components of the "Quorum sensing" gene activity regulatory system by using biological test-systems and in the polymerase chain reaction with primers to genes cepI and cepR.

[Synthesis of signaling N-acyl-homoserine-lactones participating in quorum sensing in rhizosphere and soil bacteria Pseudomonas and Xanthomonas].

Signaling molecules assigned to N-acyl-homoserine-lactones (AHL) serve as autoinducers for the genes controlling the quorum sensing regulatory system. In many gram-negative bacteria, AHL are the key factors responsible for density-dependent regulation of exoenzyme and secondary metabolite production; they also participate in interaction between bacteria and higher organisms. The soil and rhisosphere bacteria Pseudomonas and Xanthomonas from different geographical zones of Russia and the former USSR were analyzed for the presence of the AHL producers.

[Features of functioning of the promoter of microcin C51 promoter under various conditions of Escherichia coli cell growth].

The level of transcription from the promoter of the microcin C51 operon (Pmcc) depends on the growth phase of Escherichia coli cells: transcription proceeds with low efficiency at the exponential phase of growth and with higher efficiency when growth of cells is delayed during entry into the stationary phase. The functioning of Pmcc was studied in cells grown in different media by a single-copy construct, which contained the cloned promoter region of the microcin C51 operon and the promoterless lac operon. A decrease in the rate of cell growth caused by changes in the sole carbon source in minimal medium correlated with an increase in the level of transcription from the Pmcc promoter at the exponential phase of growth; the expression of Pmcc-lac during cell entry into the stationary phase was higher under unfavorable medium conditions.

[Cloning and analysis of genetic determinants determining the production of microcin B2 and B27].

Cloning of plasmid genes for the synthesis of two peptide broad-spectrum antibiotics-microcins B2 and B27- and for host cell immunity to their action was performed. Recombinant plasmids containing these genes were designated pBE108 and pVB27, respectively. Deletional derivatives of plasmid pBE108 and mutant plasmids were obtained via transposon Tn5 insertions, which did not determine production of microcin B2 and immunity to it.