|Microbial response to zinc at ecosystem and cellular levels : proteogenomic analyses of bacterial communities from contaminated sites and study of efflux systems in a model organism.
Zinc pollution is a widespread environmental problem. At the ecosystem level, monitoring the response of microbial communities to Zn is a hot topic in environmental research. At the cellular level, many Zn transport and efflux systems remain to be characterized, such as those present in the model organism Cupriavidus metallidurans CH34. The aim of the project is to investigate the bacterial response to Zn, both at the cellular and at the ecosystem levels. Microbial communities of two hot spots of Zn pollution will be characterized using metagenomics and metaproteomics. These approaches will give clues on the main microbial processes and the most abundant Zn-responsive elements. qPCR will be used to measure the abundance and dissemination of the responsive genes in situ. Controlled contaminations will be performed in laboratory microcosms. These researches will benefit from the recent transcriptomic analysis of C.
Metallidurans. In addition, the precise function and propagation rate of the Zn-responsive Tn6048 transposon will be monitored. New Zn-resistant bacteria will be isolated and characterized. We will particularly focus on the isolates from the ubiquitous and diverse Bacteroidetes phylum, a tool of choice for the study of acquisition of resistance genes through lateral transfer. At the cellular level, we will investigate in more details the function and structure of the Zne system from C. metallidurans, a RND-driven tripartite efflux complex. The activity of this potential Zn-resistance system will be investigated in vivo by transforming a Zn-sensitive strain with the zneABC genes. Protein-protein interactions and the arrangement of the different protein domains within the complex will be studied in vitro by crosslinking after reconstitution of the two membrane proteins, ZneA and ZneC, in a lipid environment. These results will allow us to build a model of protein assembly within the tripartite transport complex.|