Vibrio vulnificus Type 6 Secretion System Exhibits Influence in Marine Aggregate Colonization


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Oysters are among the most economically beneficial species with regards to aquaculture, the process of farming aquatic species. As such, in order to ensure that oyster farming remains profitable, it is necessary to maintain a product that is safe for consumption. As oysters are oftentimes consumed raw, they have been known to cause seafood-based disease, particularly from bacteria in the genus Vibrio. Vibrio infections can be costly to treat and depending on the severity of disease, can even be fatal. With sea water temperatures rising due to global climate change, infection rates have also been on the rise. There is therefore a need to rapidly develop therapies that will prevent a further number of clinical cases. Gaining a better understanding of Vibrio ecology would aid with doing so, however, data examining this is limited. Previous studies have examined higher oyster uptake levels when bacteria are integrated onto marine aggregates. This project aims to observe the relationship between three different strains of pathogenic Vibrio vulnificus species both on artificially generated marine aggregates and within oyster matrices. This study found that within both aggregate and oyster competitions the three Vibrio vulnificus strains initially displayed an “rock-paper-scissors" effect. In competition between two Environmental (E) genotype strains VV JY1305 pVSV102 (hereby dubbed VV5-102) and SREL 106 pVSV208 (VV8-208), VV5-102 was outcompeted. Strain VV5-102 was able to outcompete the Clinical (C) genotype strain VV C7184 pVSV208 (VV2-208). Unexpectedly, VV2-208 was found to be more abundant than strain SREL 106 pVSV102 (VV8-102). However, this was later understood to be the occurring due to the presence of the plasmid. There was a novel discovery made that established the type 6 secretion system plays a role in integration of V. vulnificus into natural marine aggregates. These results expand upon our understanding of Vibrio interactions as well as highlight the need for more uptake experimentation in order to create viable treatments.