ИСТИНА

A few bacteria associated with plants are able to produce volatile organic compounds (VOCs) that suppress growth of phytopathogenic microorganisms. A number of volatiles released by bacteria are also known as a plant growth stimulation factors. Volatiles are considered to be able to play the significant role in antagonistic interactions between microorganisms occupying the same ecological niches. Structures and character of VOCs produced by different bacteria are not very well studied and there is lack of information about molecular-genetic and biochemical processes of their action and synthesis. The main goal of this study was to explore the physiological, genetic and molecular mechanisms of bacterial VOCs action on phototrophic microorganisms.In the present work we studied an action of signal molecules (infochemicals) produced by soil bacteria on cyanobacterial and green algae cells. It was shown that VOCs produced by Pseudomonas (P. chlororaphis, P. fluorescens) and Serratia (S. plymuthica, S. proteamaculans) suppressed the growth of filamentous and unicellular cyanobacteria. We also assessed effects of bacterial VOCs on green algae Chlorella vulgaris and Scenedesmus quadricauda. It was found that volatile mixtures, which were synthesized by strains belonging to Pseudomonas genus (P. chlororaphis and P. fluorescens) inhibited algae growth much stronger than volatiles produced by Serratia strains. VOCs emitted by P. chlororaphis 449 and S. plymuthica strains were identified with using the gas chromatography–mass spectrometry analysis. The main headspace compounds detected were dimethyldisulfide (DMDS), some ketones and alkenes. We revealed the strong inhibition of cyanobacteria growth after treatment by individual compounds. In the result of transposon mutagenesis of the Synechococcus 7942 cells and following mutant selection we have obtained 11 cyanobacterial mutants that are resistant to 2-nonanone action, 7 mutants, which are resistant to 2-undecanone action, and 8 mutants showing the resistance to 2-heptanone action. The genes responsible for sensitivity to 2-nonanone have been identified in case of the four mutants by using of molecular-genetic methods.