Sequence analysis of the plasmid pColG from the Escherichia coli strain CA46

The complete 4715 nucleotide sequence of the plasmid pColG from the Escherichia coli strain CA46, which was originally assumed to code for colicin G activity, has been determined. Based on the nucleotide sequence homology of the 1828bp replication region, with an average G+C content of 48%, pColG was classified as a ColE1-like plasmid. Computer assisted analysis of the remaining 2887bp nucleotide sequence with an average G+C content of 34% revealed three putative OFRs. To find out whether one or all of the three ORFs code for a possible bacteriocin, a DNA fragment encompassing these ORFs has been cloned and the recombinant colonies tested for bacteriocin production. None of the colonies had an inhibitory activity against E. coli strains DH5, HB101 and MC4100. The assumption that the plasmid pColG from the E. coli strain CA46 codes for a bacteriocin thus could not be confirmed.