Regulation Of Type 3 Secretion System By Environmental Factor-dependent SRNA In Pathogenic Bacteria

Microorganism is closely related to human healthy life,while deadly infections caused by pathogenic microorganisms seriously threat to human life and handicap the development of economy as well as that of society.During the pathogenic infection,pathogens can duly express and output the virulence proteins in response to environmental stimulis.Enterohemorrhagic Escherichia coli 0157:H7 as model organism is a major food-borne pathogen that causes serious human disease.The colonization in intestinal infection is derectly connected with bacterial type 3 secretion system.Bacteria that colonize in host intestinal epithelial cells by sensing environment signals inject its effector proteins into host cell by T3SS and then mediated regulation of host cell signaling pathways.However,the relationship between the environment signals and mechanism of T3SS protein output has not been clarified.Recent researches show that a class of non-coding small RNA with regulatory role found in bacteria is closely linked to the complex regulatory network of stress response and the expression of virulence genes.These sRNAs have a significant role in the regulation of transcription factors and virulence genes expression,outer membrane protein synthesis,lipopolysaccharide modification,biofilm formation,quorum sensing,and so on.sRNAs can respond to changes in host intestinal microenvironment and then regulate the bacterial metabolism,especially expression of virulence genes.In this paper,MicA as a sRNA build a bridge between the environment signal stimulation and T3SS protein secretion.High concentration of NaCl induced the expression of MicA,and weakened the level of T3SS protein secretion.However,the changes in pH did not activate the expression of MicA and could influence the level of T3SS protein secretion.The inhibitory effect of MicA overexpression on T3SS protein secretion may be due to the complementary base pairing with ler mRNA and implement the post-transcriptional regulation.And the inhibitory effect may also be mediated by other targets,such as grlR.Moreover,there may be a connection between MicA,OMVs and T3SS protein output.However,the regulation of MicA in different strains was different.This topic preliminarily illustrates the importance of sRNA in T3SS regulation of EHEC 0157:H7,which has a guiding significance and provide the scientific basis for controling the incidence of EHEC infections.