Screening And The Quorum Sensing System Of Pseudomonas Aeruginosa Resistance Gene

Pseudomonas aeruginosa is an opportunistic pathogen. It can cause seriously acute and chronic infections in human beings and it is one of leading pathogens in hospital. The infection is difficult to eradicate because P. aeruginosa has high innate drug resistance to many antimicrobial drugs. Searching resistant genes and investigation of drug resistance mechanisms in P. aeruginosa is critical to control its infections.Seven antibiotics were utilized to screen transposon mutation library of P. aeruginosa. Susceptible mutants which exhibit increased drug susceptibility by 3 times and resistant mutants which exhibit decreased drug susceptibility by 8 times were obtained after screening about 17 thousands transposon mutants. The position of the transposon in the genome was determined by arbitrary PCR, DNA sequencing and comparison to the P. aeruginosa genome. Many new genes involved in drug resistance were discovered.Quorum-sensing system is widely employed by bacterial to coordinate communal behavior in response to population density. PA4350 is a gene of unknown function with high similarity to lasR and rhlR of quorum sensing system in P. aeruginosa, and it is hypothesized to be involved in the process of quorum sensing. By monitoring the expression of promoter-lux reporter plasmid we found that there was no connection between PA4350 and las/rhl system and PA4350 had no effect on the expression of virulence-related genes.plcH encodes haemolytic phospholipases C which is an important virulent factor in Pseudomonas aeruginosa. Using hemolysis test blood agar plate we found that hemolysis was affected by quorum sensing system in Pseudomonas aeruginosa. The promoter region of plcH that encodes haemolytic phospholipases C was cloned upstream of promoterless luxCDABE reporter and the expression of plcH was examined in quorum sensing mutants. The result indicates that the gene plcH was positively regulated by the quorum-sensing system.The results obtained in this study provide important information for better understanding quorum-sensing system and pathogenesis of Pseudomonas aeruginosa and for exploring new drug resistance mechanisms and novel antimicrobials.