Molecular weapons: the type III secretion system

Abstract

Most bacteria are beneficial to humans but some of them are able to infect us and cause disease, due to virulence factors. An important virulence factor is the type III secretion system (T3SS) that bacteria use as a molecular weapon that allows them to inject toxins into our cells causing death. One of these bacteria is Pseudomonas aeruginosa, an opportunistic pathogen that can be resistant to multiple antibiotics. Moreover, these bacteria can communicate with each other and coordinate a group behavior by the quorum sensing systems (QS) that activates the production of virulence factors. The T3SS activation depends upon on the ExsA protein that is regulated at transcriptional and translational levels by the QS and Rsm systems, respectively. Since inactivation of the T3SS impairs the virulence of this bacterium, it is important to understand the mechanisms that control its expression, which will allow the design of strategies to avoid its activation and thus assist to the treatment of the infections caused by this microorganism.

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