Insights into the Bacterial Type III Secretion System

Abstract

Bacterial type III secretions system (T3SS) is a membrane embedded needle like macromolecular complex structure present in Gram negative bacteria and mostly found in Yersinia, Salmonella, Shigella, Entero Pathogenic E. coli (EPEC), Entero Haemorrhagic E. coli (EHEC) and Pseudomonas aeruginosa. The infection dynamic involves several sub cellular components for easy delivery of the effector molecules from bacteria to the host cells to survive the host immune mechanism. Mainly three categories of proteins are involved- structural, translocator and effector proteins. T3SSs can be classified into seven phylogenetic families, based on the genetic analysis of their components. Multiple T3SSs are found in the same bacteria with the purpose of causing infection in multiple steps.Their contribution to virulence mechanism is mainly through modification of the host cytoskeleton system or interfering with the signaling Pathways in the host cellular events related to the defensive mechanism. The infection requires multi-step regulatory strategies which include spatiotemporal regulation of a different set of effector proteins encoded genes. Despite their contribution in virulence mechanism, they can be utilized by re-engineering them to deliver either various therapeutic protein agents or could be used as an alternative novel approach for antigen delivery into the host. Apart from its use as the delivery platform they can be targeted using broad spectrum inhibitors against diverse sets of T3SS mediated diseases. Therefore, this review summarizes the basic structure, its regulatory mechanism in different bacteria and the future perspective.