Analysis of the effect of copper on the virulence of a pathogenic Edwardsiella tarda strain

Abstract

Aim: To investigate the effect of copper on the virulence of Edwardsiella tarda. Methods and Results: The pathogenic Edw. tarda strain TX5 was cultured under copper‐stressed conditions and examined for any potential alteration in capacities that are associated with pathogenicity. The results showed that compared to untreated TX5, Cu‐treated TX5 exhibits reduced planktonic and biofilm growth, an impaired ability to adhere to host mucus, modulation of host immune response, and dissemination in host blood and liver. Consistent with these observations, the overall bacterial virulence of Cu‐treated TX5 is significantly attenuated. SDS‐PAGE analyses of whole cell protein production showed that Cu‐treated TX5 differs from the untreated TX5 in its production of at least one protein. Quantitative real time reverse transcriptase PCR analyses showed that copper treatment decreased the expression of virulence‐associated genes encoding components of the type III and type VI secretion systems, the Eth haemolysin system, and the LuxS/AI‐2 quorum‐sensing system. Conclusions: Prolonged exposure to copper has multiple effects on TX5 and results in significant attenuation of bacterial virulence. Significance and Impact of the Study: The results of this study demonstrate that copper treatment has a broad and profound effect on the virulence‐associated capacities of TX5, which is exerted at least in part at the transcription level. These findings provide new insights to the antimicrobial mechanism of copper.

Responses to copper stress in the metal‐resistant bacterium Cupriavidus gilardii CR3: a whole‐transcriptome analysis

“…Low concentration copper has been reported to exert a negative effect on Edwardsiella tarda TTSS, which is in contrast to our findings. The minimum inhibitory concentration (MIC) value to copper in E. tarda is 1.6 mM, whereas MIC value in strain CR3, it is 3 mM . We, therefore, hypothesize that TTSS activation is due to the higher resistance to copper of strain CR3.…”

Nooks and Crannies in Type VI Secretion Regulation

“…The Edwardsiella tarda evp cluster is induced at low temperatures (89) or in the presence of iron or copper (52,109). Regulation by iron levels has been reported for F. tularensis and Y. pestis (35,64,84) and for the enteroaggregative E. coli sci-1 gene cluster (Y. R. Brunet and E. Cascales, unpublished results).…”

Type VI secretion system regulation as a consequence of evolutionary pressure

“…The VirAG TCS is crucial for B. mallei virulence and regulates genes involved in actin tail formation, capsule production and the T6SS (Schell et al, 2007). Recently, a T3SS cluster 3 (T3SS-3) regulator, BspR, was identified in B. pseudomallei that also regulates the T6SS-1 cluster (Sun et al, 2010). Mutation of bspR reduced T6SS-1 gene expression compared with that of the parent strain when grown in liquid culture (Sun et al, 2010).…”

“…Recently, a T3SS cluster 3 (T3SS-3) regulator, BspR, was identified in B. pseudomallei that also regulates the T6SS-1 cluster (Sun et al, 2010). Mutation of bspR reduced T6SS-1 gene expression compared with that of the parent strain when grown in liquid culture (Sun et al, 2010). BspR is a TetR family regulator involved in a complex regulatory cascade that includes downstream regulators BprP, BsaN, BicA and BprC.…”