INFLUENCE OF THE EXOGENOUS QUORUM SENSING AUTOINDUCERS ON PSEUDOMONAS AERUGINOSA RHAMNOLIPIDS BIOSYNTHESIS

The aim of this investigation was to discover the effect of Pseudomonas aeruginosa exogenic QS autoinducers: N-(3-oxo-dodecanoyl)homoserinlacton (3-oxo-С12-HSL), N-butiryl-homoserinlacton (С4-HSL), and 2-heptyl-3-hydroxy-4-quinolon (PQS) on P. aeruginosa АТСС 15692 mono- and di-rhamnolipids biosynthesis. Methods. Pseudomonas aeruginosa АТСС 15692 were cultured on Giss medium with 2% glucose at 37 оС for 24 h. The investigations were performed in «plancton-biofilm» system with using of «Nunclon» 48-well plates. Di- and monorhamnolipids separation was conducted by TLC methods on Alugram Sil G /UV 254 TLC plates. Di- and monorhamnolipids were eluted separately and their content was determined by the orcinic test. Dirhamnolipids /monorhamnolipids ratio was calculated taking a monorhamnolipids content as 1 unit. There were used in this work homoserinlactones (Sigma Aldrich) and 2-heptyl-3-hydroxy-4-quinolon synthesized in ONU Biotechnological scientificeducational center. Results. It was determined that exogenous 3-oxo-С12-HSL showed no effects on rhamnolipids biosynthesis. In presence of the two others autoinducers: С4-HSL and PQS, rhamnolipids content increases. С4-HSL at the concentrations of 5 and 10 μM caused increasing of the biosurfactants biosynthesis in 3.4 and 4.1 times. In presence of PQS in 40-80 μM concentration range a proportional increase in the synthesis was observed. Its level increased in 1.9; 3.3 and 5.2 times in presence of 40, 60 and 80 μМ signaling quinolon concentration respectively. After 24 hours of incubation di- and monorhamnolipids ratio was 2,2:1. In presence of С4-HSL it was 2:1 at the concentration of this autoinducer 5 μМ and 2,4:1 at the concentration of 10 μМ N-butiryl-homoserinlacton. Conclusions. PQS greatly increased dirhamnolipids biosynthesis, especially Rha-Rha-C10-C10. At PQS concentration of 40, 60 and 80 μМ Rha-Rha-C10-C10 /Rha-C10-C10 ratio was 3:1, 3,6:1 and 4,5:1, respectively. It was shown that supernatants of bacterial cultures, contained increased amounts of dirhamnolipids, showed the highest emulsifying activity.