Theses and Dissertations


Ali Akgul

Issuing Body

Mississippi State University


Karsi, Attila.

Committee Member

Peterson, Daniel.

Committee Member

Thornton, Justin A.

Committee Member

Lawrence, Mark L.

Date of Degree


Document Type

Dissertation - Open Access


Veterinary Medical Science

Degree Name

Doctor of Philosophy


College of Veterinary Medicine


Veterinary Medical Science Program


Edwardsiella ictaluri is an intracellular Gram-negative pathogen, causing enteric septicemia of catfish (ESC). Universal stress proteins (USP) are important in bacterial virulence, but the role of USPs in E. ictaluri virulence is not explored yet. Our aim was to analyze gene expression of 13 usp (usp01-usp13) and 7 USP-interacting genes (groEL, groES, dnaK, dnaJ, clpB, grpE, and ppGpp) under low pH, H2O2, catfish serum, and in vivo stress conditions, construct USP mutants, and determine mutants’ role in E. ictaluri virulence. We found that usp05, usp07 and usp13 genes were highly expressed under all stress conditions, while groEL, groES, dnaK, grpE, and clpB were highly expressed in oxidative stress. Among the 10 E. ictaluri USP mutants, Eiusp05-07-08-09-10, and 13 were significantly attenuated in catfish and highly protective against wild type E. ictaluri infections in catfish. Eiusp05-07-08-09, and 13 were sensitive to oxidative stress, and all mutants were sensitive to pH exposure.