Isolation of colicinogenic E. coli, optimization of colicin production and transformation of Col plasmid.

ABSTRACT

An attempt was made for the isolation of colicinogenic E. coli from cow and sheep dung samples. Total of 112 E. coli isolates were collected from sheep and cow dung samples in which 63 isolates are from cow dung and 49 isolates are from sheep dung samples. In the screening for colicin production, two E. coli isolates C22 and C51 from cow dung sample and one isolate S39 from sheep dung sample showed activity against the pathogenic strain E. coli O157H7. Colicin production by all the three E. coli isolates was found to be enhanced by 0.25mg/l of mitomycin-c and three hours of incubation at 370C. Plasmid DNA was isolated from colicinogenic E. coli strains by alkali lysis method and their molecular weight was found to be 6.5 kb. The transformation experiment carried out with the standard strain E. coli DH5 confirmed that the plasmids were col-plasmids. The three colicinogenic E. coli strains isolated in this study will be a candidate to develop as probiotic for veterinary applications.