Role of tripartite efflux pumps in pyoverdine secretion in Pseudomonas putida KT2440

• Applicant: Professor Dr. Heinrich Jung
• Subject Area: Metabolism, Biochemistry and Genetics of Microorganisms
• Term: since 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 430651076

Bacterial efflux pumps are best known for their role in the export of toxic compounds such as antibiotics. We and others have shown that certain efflux pumps are also responsible for the secretion of siderophores. Siderophores are common goods that can potentially be used by all related cells in a community to acquire iron ions that are important for metabolism. Siderophores are often species-specific and thus also competitive factors that inhibit the growth of unrelated microorganisms. Thus, siderophore secretion not only enables bacterial growth under iron-deficient conditions, but also influences interactions between bacteria and between bacteria and eukaryotic hosts. In the first funding period, we identified the efflux pumps PvdRT-OpmQ (ATP dependent), MdtABC and ParYX (both proton motor force dependent) of the plant growth promoting soil bacterium Pseudomonas putida KT2440 as important for the secretion of the siderophore pyoverdine. To this end, growth, secretion and intracellular accumulation of pyoverdine were analyzed in mutants. Furthermore, we were able to purify components of the PvdRT-OpmQ system and use biochemical methods to actually detect interactions between the detergent-solubilized protein and pyoverdine. As a continuation of this work, we will now (1) elucidate the molecular mechanism of the PvdRT-OpmQ system using the reconstituted and assembled components of the system. This will include transport kinetics, substrate specificity, principles of energization, and functionally important interactions with other proteins. (2) The influence of oxidative and acidic stress on the secretory activity of PvdRT-OpmQ will be investigated in vitro and in vivo. These studies will also include the influence of a stress-induced modulation of pyoverdine secretion on social interactions in Pseudomonas populations. We expect to gain new insights into the role and molecular function of bacterial efflux pumps. In the long run, the results may help to specifically modulate pyoverdine-mediated interactions between organisms, to improve bioremediation processes and to optimize therapeutic measures against drug-resistant pathogens, such as the use of pyoverdine-drug conjugates.

• DFG Programme: Research Grants