Study Of The Carbon Starvation Induces The Expression Of PprB Regulated Genes In Pesudomonas Aeruginosa

Pseudomonas aeruginosa is a ubiquitous opportunistic pathogen responsible for many human infections.This bacteria often adopt a biofilm lifestyle that is hard to treat.In several previous studies,the PprA.PprB two-component system(TCS)which controls the expression of type TVb pili,BapA adhesin,and CupE fimbriae was shown to be involved in biofilm formation.The PprA-PprB two component system have been studied for over ten years,PprB regulon containing multiple functional gene clusters were characterized several years ago.However,signals or environmental conditions that can trigger the PprA-PprB TCS are still unknown,and the molecular mechanisms of PprB mediated biofilm formation are poorly characterized.As it comes to the physiological role of PprB in bacteria,previous studies are mainly related to the phenotypes of PprB overexpression strain which,compared with the wild type strain,showed increased cell membrane permeability and aminoglycosides sensitivity,decreased cellular cytotoxicity and virulence in flies,and better biofilm formation.However,very few results were presented about the phenotypes of PprB mutant,except one recent research that had observed a compromised biofilm in this strain.Generally,finding out the external signals which can trigger a regulatory system is usually crucial to understand the regulatory logic and the inward function of that system.In this study,we reported that carbon starvation stress(CCS)can induce the expression ofpprB and genes in PprB regulon.The stress response sigma factor RpoS,rather than the two component sensor PprA,was determined to mediate the induction of pprB transcription.We also observed a strong negative regulation of PprB to the transcription of itself.Further experiments showed that PprB overexpression greatly enhanced the cell-cell adhesion(CCA)and cell-surface adhesion(CSA)in P.aeruginosa.In PprB overexpressed strain,mutant of the BapA adhesin and CupE fimbriae displayed compromised CCA and CSA,while the type ?b pili showed an unexpected negative effect on CCA and no effect on CSA.In addition,expression of PprB regulon genes displayed significant increases in 3-day colony biofilms,indicating a possible carbon limitation state in biofilms.The CSS-RpoS-PprB-BapA/Flp/CupE pathway identified in this study provides a new perspective of the proeess of biofilm formation.