Survival and detection of an introduced Escherichia coli containing the porcine somatotropin gene from a waste treatment microcosm

The number Escherichia coli containing the porcine somatotropin (pST) gene cloned into plasmid pBR322 recovered from a laboratory-scale waste treatment microcosm decreased over a period of several days following their introduction. The pST gene was detected by hybridization analysis in these bacteria when recovered from authentic wastewater at 72 h after introduction, but the gene was not detected in bacteria recovered at 144 h. No significant difference in recovery, as judged by auxotrophic and antibiotic-resistance markers, was noted between the pST-containing strain and an isogenic E. coli without pST, indicating that presence of the pST gene confers no survival advantage or disadvantage on the bacterial host.