Comparison of the Structure, Regulation and Functions between TypeThree and Type Six Secretion System in Gram-Negative Bacteria

Abstract

Bacteria have evolved multiple protein secretion systems to survive and cope with surrounding environmental stresses. So far, there are seven secretion systems (type I to type VII), which have been identified and demonstrated the structural and molecular mechanisms. Among them, type three secretion system (T3SS), hallmark of acute infection, is considered as the most complicated system and can translocate effector proteins directly into host cell through a needle-like apparatus. Type six secretion system (T6SS) targets both prokaryotic and eukaryotic cells using a bacteriophage-like structure and plays a role in pathogenesis and bacterial competition. This review is based on our understanding of comparison of the structure, regulation, function and application between T3SS and T6SS. Understanding the structural and functional mechanisms, as well as the difference and relationship between these two secretion systems will help our understanding of bacterial pathogenesis and interspecies interaction.