The Role Of Acyltransferase Encoding Gene PA3242 In Pseudomonas Aeruginosa

Pseudomonas aeruginosa is an opportunistic pathogen that causes 10%chronic infections in hospital.Meanwhile,PAO1 shows robust resistance to a wide range of antibiotics and imposes great pressure on clinical treatment.The infection is usually lethal to patients with compromised immune system.The outer membrane of PAO1 contributes a lot to antibiotic resistance for its low permeability that prevents antibiotics from entering PAO1.The outer layer of outer membrane is mainly formed by LPS and Lipid A is the hydrophobic molecule that incorporates LPS to the outer membrane tightly.Nowadays,modifications of Lipid A is deemed as one of the most promising projects for anti-pseudomonad therapy.PA3242 and PA0011 are predicted as acyltransferase encoding genes that involve in the synthesis of Lipid A.The function of PA0011 has been investigated previously.To further investigate the mechanism of Lipid A secondary acylation,the function of PA3242 has been researched thoroughly and compared with that of PA0011.PA3242 is essential for the growth of PAO1.Deletion of PA3242 severely jeopardized the growth of PAO1(aPA3242)in nutrient medium LB,while PAO1(?PA0011)exhibited similar growth rate compared with PAO1.Moreover,the transcription of'PA3242 is negatively regulated by temperature.The expression of PA3242 is 4 folds higher at 28? compared to that of PA3242 at 37?.Although the expression of PA0011 is also increased at 28?,it's expression level is far more less than that of PA3242.Overexpression of PA4997,the Lipid A flippase encoding gene of PAO1,recovered the growth of PAO1(?PA3242),which suggested that PA3242 may involve in the transportation of Lipid A.PA3242 is important for the integrity and stability of outer membrane and has great influence on antibiotic resistance.The result showed that PAO1(?PA3242)is hypersensitive to a wider range of antibiotics compared to PAO1(?PA0011).and PAO1.Furthermore,the tolerance of PAO1(?PA3242).to metal-chelator is also severely compromised compared to PAO1(?PA001 1)and PAO1.PA3242 has great influence on the virulence of PAO1.Three aspects of virulence,the cytotoxicity,infection capacity and pathogenicity,were evaluated.The results demonstrated that the virulence of PAO1(?PA3242)is seriously attenuated compared to PAO1(?PA0011)and PAOl.The compromised virulence of PAO1(?PA3242)is probably caused by the deficiency of pilus,which is necessary for the motility of PAO1.In conclusion,the PA3242-dependent Lipid A secondary acylation play a predominant role in antibiotic resistance and virulence compared to that of PA0011.Moreover,PA3242 may also involve in the transportation of Lipid A and plays an important role in the growth of PAO1.These make PA3242 an excellent target for anti-pseudomonad therapy.