Transcriptional Regulation And Function Of Zinc Uptake Systems In Vibrio Cholerae

Zinc is an essential trace metal required for numerous cellular processes in all forms of life.Amount of intracellular zinc are highly regulated,because too little zinc does not support growth,while too much is virous.In order to maintain zinc homeostasis,bacteria have developed several transport systems to regulate its uptake.V.cholerae is a Gram-negative bacterium and the causative agent of the severe waterborne disease cholera.Characterized by devastating rice-water diarrhea,dehydration,and death,cholera is still a major public health issue in developing countries.V.cholerae resides in aquatic reservoirs,and upon ingestion by a human host,it transitions to a pathogenic lifestyle.Commensal bacteria in the host may also limit zinc availability.Consequently,many bacterial pathogens must be able to acquire zinc in order to cause disease.A number of pathogens require the ZnuABC transporter system to coloinize hosts.However,it is less clear how another important pathogen,Vibrio cholerae,regulates its zinc homeostasis in different environmental niches and whether zinc uptake systens contribute to its pathogenesis.In this study,we investigated zinc transport systems in the enteric pathogen Vibrio cholerae,the causative agent of cholera.Bioinformatic analysis predicts that two gene clusters,VC2081 to VC2083(annotated as zinc utilization genes znuABC)and VC2551 to VC2555(annotated as zinc-regulated genes zrgABCDE),are regulated by the putative zinc uptake regulator Zur.Using promoter reporter and biochemical assays,we confirmed that Zur represses znuABC and zrgABCDE proiloters in a Zn2+-dependent manner.Under Zn2+-limiting conditions,we found that mutations in either the znuABC or zrgABCDE gene cluster affeet bacterial growth,with znuABC mutants displaying a more severe growth defect,suggesting that both ZnuABC and ZrgABCDE are involved in Zn2+ uptake and that ZnuABC plays the predominant role.Furthermore,we reveal that ZnuABC and ZrgABCDE are important for V.cholerae colonization in both infant and adult mouse models,particularly in the presence of other intestinal microbiota.Nurerous bacterial cells need zinc uptake systems for growth and virulence.The study presented here exhibited that the gut microbio me in host intestine decreases the availability of zinc.As enteropathogenic bacteria,V.cholerae will lose the capacity of reproduction and colonization without a high-affinity zinc transporter.This is the first description of zinc competition between V.cholerae and microbiota in the small intestine part of host.These results might provide some views for microbial pathogenesis and the interactive relationships between host metabolism and gut microbiome.Collectively,our studies indicate that these two zinc transporter systels play vital roles in maintaining zinc homeostasis during V.cholerae growth and pathogenesis.