Genome-Wide Transposon Screen of a Pseudomonas syringae mexB Mutant Reveals the Substrates of Efflux Transporters

Bacteria use protein pumps to remove toxic compounds from the cell interior, enabling survival in diverse environments. These protein pumps can be highly redundant, making their targeted examination difficult. In this study, we exposed mutant populations ofPseudomonas syringae to diverse toxicants to identify pumps that contributed to survival in those conditions. In parallel, we examined pump redundancy by testing mutants of a population lacking the primary efflux transporter responsible for toxin tolerance. We identified partial substrate overlap for redundant transporters, as well as several pumps that appeared more substrate specific. For bacteria that are found in diverse environments, having multiple, partially redundant efflux pumps likely allows flexibility in habitat colonization.