Investigation The Role Of PA4591 And An Operon PA4591-PA4594 In Pseudomonas Aeruginosa

Pseudomonas aeruginosa (PA) is an important opportunistic Gram-negative pathogen leading to nosocomial infections. It is the major cause of morbidity and mortality among compromised patients such as HIV patients, burn victims and cystic fibrosis (CF) patients.The infection by P. aeruginosa is difficult to eradicate due to both high intrinsic and acquired resistance to a wide variety of antibiotics including carbapenems. The emergence and spread of strains with resistance to kinds of antibiotics, especially to carbapenems, post a challenge to the success of antibiotics therapy.It is crucial to investigate the molecular mechanisms of antibiotic resistance as well as pathogenesis in order to optimize antibiotic chemotherapy and find new drug targets, against P. aeruginosa infections.PA4591 was identified from the screened for the genes involved in the resistance to imipenem (Imp), meropenem (Mem) and biapenem (Bip) in PAO1 with the obviously increased resistance to the three carbapenems compared with the wild type PAO1. The further study of PA4591 was carried out in this study.The protein encoded by PA4591 belongs to the HlyD family secretion protein is involved in the transporter of hemolysin. As shown by assay of blood culture, significant lose of hemolysis ability was observed in the PAO1(△4591) mutant. The expression of mexAB-OprM increased more than two times in PAO1(△4591) compared to the wild type. The elevate expression of mexAB-OprM in PA4591 mutant may account for the increased carbapenem resistance partially. The elevate expression of mexAB-OprM caused the decreased PQS and consequently decreased pyocyanine production and protease production. Then, As shown by using a Drosophila melanogaster infection model and a Chinese cabbage (Brassica pekinensis) infection model, significant decreased virulence was observed in the PAO1(△4591) mutant when compared to the wild type.By bio-information analysis, PA4591 together with PA4592, PA4593 and PA4594 may consist an ABC transporter for the transport of hemolysin. Not any other research about the transport of hemolysin was reported before in P. aeruginosa. In this study, PAO1(△4591)、PAO1(△4592) and PAO1(△4593) lose the ability of hemolysis, which suggested that this ABC transporter formed by PA4591 to PA4594 plays an important role in the transport of hemolysin in P. aeruginosa. However, PAO1(△4594) did not lose the ability of hemolysis. We supposed that there would be other energy contributing to the transport of hemolysin. In addition, the decreased susceptibly of PAO1(△4592) and PAO1(△4593) to carbapenems was observed in this study. In conclusion, the ABC transporter consisted by PA4591, PA4592, PA4593 and PA4594 plays an important role in transport of hemolysin as well as antibiotic susceptibly.