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Page No. : 13-18

ABSTRACT

The present study was conducted to isolate and characterize genus specific cytotoxic proteins of salmonellae and compare these with that of Shigella flexneri. The cell lysates of Salmonella serovars (20) and S. flexneri (1) were prepared by disintegrating the bacterial cells with ultra-sonication. The sonicates were centrifuged and obtained supernatants were made bacteria free and then subjected to gel filtration using Sephacryl S-200 HR through Fast Protein Liquid Chromatography (FPLC). The chromatographic profiles of the cell lysates of all Salmo- nella serovars as well as S. flexneri revealed four distinct peaks at similar location in their preparations. The peak contents of S. Typhimurium and S. flexneri were differentiated on the basis of cytotoxicity and molecular weight. The fourth peak contents of S. Typhimurium and S. flexneri showed maximum toxicity when tested on MDBK, BHK 21 and VERO cells and the cytotoxic effects being more intense with S. flexneri. The BHK 21 and MDBK cells appeared to be quite promising than the VERO cells during in-vitro assays. On SDS-PAGE analysis, the fourth peak contents of S. Typhimurium and S. flexneri revealed 3 and 4 peptide bands, respectively, with molecular weight of 65.59, 46.47 and 36.48 kDa as well as 66.87, 57.76, 35.89 and 32.45 kDa. In Western blotting, a peptide band of MW 65.59 kDa present in the fourth peak of S. Typhimurium was found to be immunogenic which could be later exploited as a tool for detection of salmonellae in foods.

Keywords: Cytotoxin, fast protein liquid chromatography, S. flexneri, S. Typhimurium, SDS-PAGE, Western blotting