Mukhlis A. The rhamnolipids biosynthesis in Pseudomonas aeruginosa in the presence of the exogenous autoinducers of intercellular cooperation

The thesis is devoted to the study of rhamnolipids biosynthesis by four Pseudomonas aeruginosa in presence of quorum sensing exogenous autoinducers. It was shown that biosurfactants biosynthesis in P. aeruginosa strains activated in late log-phase, and after transition into stationary phase rhamnolipids level increase permanently, depending the time of incubation. Rhamnolipids biosynthesis in "planctonic-biofilm" system was more effective than in suspension. It was shown that 3-oxo-С12-HSL has no effects on rhamnolipids biosynthesis. С4-HSL increase summary rhamnolipids level in 2,5-4 times, but show no effects on dirhamnolipids/monorhamnolipids ratio. PQS stimulate biosurfactants biosynthesis depend the concentration (in the range of 20-80 µМ) in 2-6 times. It was shown that PQS synthetic analogs activity depends of there acyl chain length: octyl-quinolon (С8) > nonyl-quinolon (С9) > lauryl-quinolon (С11) and they activity were lower than PQS activity. It was shown that PQS contributes to the enrichment of rhamnolipids mixture with dirhamnolipids, increase Rha-Rha-C10-C10/Rha-C10-C10 ratio from in 1,9-2,6 times.It was shown for the first time that PQS, depend the concentration, increase rhamnosyltransferase 2 activity in 30-93%. Rhamnosyltransferase 2 kinetic study shown that in presence of PQS an affinity of enzyme to substrate increase, as evidenced by the decreasing of Km in 1,5 times.