Study The Role Of Escherichia Coli Quorum Sensing Gene YdiV On Phage Infection

Bacteria have been thought to be archetypal single-celled individuals exist in the environment,and without mutual coordination behavior between each others for a very long time.Just in past several decades,quorum sensensing(QS)system has been found that can detect population density and regulate the physiological function of bacterial population,and enable the individuals to coordinate their behaviour,show multicellular and social hierarchy,and enhance survival of bacteria in the environment.QS has been clarified to be involved in many important physiological functions of bacteria,such as bio-luminescence and stress resistance.Unfortunately,there are few reports about the role and function of QS in phage infection.In this paper,Escherichia coli BW25113 and T4 phage were used as the experimental materials.Severial QS related gene ydiV,sdiA knockout and complementary strains were constructed by using homologous recombination technology.The infections of T4 phage in different bacterial strains were determined.The strians of ?ydiV,?sdiA and Wt reached the stable period at about 12,11 and 11 hours of incubation.The burst size of ?sdiA,?ydiV and Wt have no significant difference;but the infection rate is varied,?ydiV showed the average reduction of about 22%than Wt and the complementary strain showed increasment about 15%than Wt,which imply that ydiV genes involved in the interaction with T4 phage.The lysis activities of three bacterias decreased by 10%-15%after treated with AHL.It suggests that QS is evidently involved in the host defense against phage's infection and it should not be the only pathway in E.coli.Finally,a preliminary study was made to explore the mechanism of QS involved in phage infection.No significant difference of adsorption rate between defect and the wild type stains was observed.Genes of bcsA,ompC,waaA,waaQ,hemH,recA and rcdA that associated with QS were selected and their expressions leveal were detected by RT-PCR.In the ?ydiV,regardless of the bacteriophage T4 infection,the expressions level of bcsA,ompC,waaA,waaQ and recA were lower than the wild-type and revertant strain.The expression level of hemH was lower than wild type only after T4 infection,while rcdA expression was higher than wild type,and the expression level was decreased after T4 phage infection.All results showed that ydiV is likely to affect the adsorption and infection of the phage by regulating the synthesis of bacterial LPS and changing the structure of biofilms.This is the first report about the function and role of quorum sensing system,especially the ydiV gene involved in interaction of host and phage infection in E.coli.