Yu, Li2024-08-142024-08-1419981998https://hdl.handle.net/1828/18711Proaerolysin is secreted by Aeromonas salmonicida and Aeromonas hydrophila via the General Secretion Pathway (GSP). Research presented in this thesis focused on the second step of the GSP, the Main Terminal Branch (MTB). Several approaches were taken to learn more about this process. Although a large amount was secreted into the extracellular medium, some proaerolysin accumulated inside the cell. The intracellular proaerolysin was localized both in the periplasm and in association with the inner membrane. The proaerolysin was calculated. A study of the effect of proaerolysin secretion on protease secretion showed that the appearance of protease in the culture supernatant was greatly reduced when proaerolysin secretion approached the maximum, suggesting that there was an upper limit to the GSP-MTB. A study of secretion of domain II-IV of proaerolysin showed that domain II-IV could be secreted by itself. The secretion was poor compared to secretion of wild-type proaerolysin. When coexpressed with domain I of proaerolysin, domain II-IV did not show a great increase in secretion. However, parallel studies in our laboratory showed that secretion of both domain I and domain II-IV were increased when they were coexpressed in another way (Diep et al., in press). The Clostridium septicum α-toxin could not be secreted by A. salmonicida, despite the similarity in DNA sequence between α-toxin and aerolysin.157 pagesAvailable to the World Wide WebThesis