The Study On The Infection Mechinism Of A Novel Two-component System ResS/ResR Of Streptococcus Suis 2

Bacteria have evolved sophisticated mechanisms to monitor,adapt,and respond to environmental and host-mediated assaults.For bacterial pathogens,they have evolved virulence factors and regulation systems that allow adaptation to different environments within a host ensuring their survival.A common regulatory system shared by a wide range of bacteria is the two-component signal transduction systems(TCS).Experiments described in this study examine the role played by the resS-resR system in Streptococcus suis 2 virulence,metabolism, and adaptation to adverse environments.The author performed a detailed structural and functional analysis of a novel two-component system(ResS/ResR) in Streptococcus suis serotype 2(S.suis 2).To examine the role of the ResS/ResR system in pathogenesis,we constructed unmarked deletion mutants AresR,AresS,AresS/R and compared biochemical,gene expression and virulence properties with the wild type parent strain.The AresS/R double mutant exhibited multiple phenotypic changes including a substantially reduction in haemolytic activity and reduced sialic acid.All three mutants had reduced adhesion to Hep-2(epithelial cells) compared to wild-type.Comparative virulence was studied in a CD1 mouse model.A 2 log increase in LDs0experiment was found for theâ–³resS/R mutant strain.Theâ–³resS/R mutant was attenuated for infection in a mouse model,heavy histological changes being observed in AresS/R mutant compared to wildtype. Only minor histological changes have been observed in AresR andâ–³resS mutant strains compared to wildtype.As adjudged by real-time quantitive RT-PCR,gene expression of the known virulence genes sly,mrp and ef were substantially down-regulated both in vitro and in vivo.The ResS/ResR two-component system is essential for S.suis 2 virulence.The author present evidence to demonstrate that theAresS/R mutant of Streptococcus suis is less sensitive to adverse environmental conditions,deficient in some important biochemical characters,lacks haemolytic activity,exhibits defects in colonization,and is avirulent in a mouse infection model.On the basis of these finding and by assaying some important genes expression profile,the authors found that clinical S.suis 2 isolates from infected pigs had distinct gene expression patterns during the growth in standard laboratory media and on soft-tissue infection models of disease.The authors conclude that the ability of S.suis 2 to remodel its transcriptome plays a major contribution in its ability to produce hemolysin and colonize distinct niches of the body and cause disease.