Type Six Secretion System (T6SS) in Aquatic Pathogens

For aquaculture to overcome challenges in diseases, preventive and therapeutic interventions are needed. One solution of great potential is the use of bacterial nanomachines. Protein secretion systems facilitate nutrient acquisition, communication, and disease by delivering virulence factors. The Type VI secretion system (T6SS) is one of the protein secretion systems that is extremely widespread and targets bacterial and eukaryotic cells for fitness and pathogenicity. The T6SS function can be redirected as a target for vaccine development and therapeutics for aquaculture applications. Choosing a strain that encodes T6SS and understanding its function and activity is vital to accomplishing this. This review outlines the current knowledge on the function, organization, and regulation of T6SS in aquatic pathogens, including important fish and crustacean pathogens Vibrio, Aeromonas, Edwardsiella, Flavobacterium, Pseudomonas, and Francisella. Overall, the T6SS in Vibrio and Edwardsiella are the two well-studied groups to date. The review identifies research gaps and directs future studies to develop technologies to control diseases caused by pathogens of aquaculturally essential species. Future research and development on T6SS can be applied to important, newly emerging, and re-emerging bacterial, viral, and fungal diseases.