What is type VI secretion doing in all those bugs?

摘要

The identification of bacterial secretion systems capable of translocating substrates into eukaryotic cells via needle-like appendages opened fruitful and exciting areas of microbial pathogenesis research. The recent discovery of the type VI secretion system (T6SS) was met with early speculation that it too acts as a needle that pathogens aim at host cells. New reports demonstrate that certain T6SSs are potent mediators of interbacterial interactions. In light of these findings, we examined earlier data indicating its role in pathogenesis. We conclude that while T6S – in rare instances – can directly influence interactions with higher organisms, the broader physiological significance of the system is likely to provide defense against simple eukaryotic cells and other bacteria in the environment. The critical role of T6S in bacterial interactions, along with its presence in many organisms relevant to disease, suggest that it may be a key determinant in the progression and outcome of certain human polymicrobial infections.