Tetracycline-Resistant Gene of a Non-Transferable R Plasmid from Fish-Pathogenic Bacteria Aeromonas salmonicida

Abstract

The non-transferable drug resistance plasmid pJA8102-2 encoded with tetracycline resistance was detected in the bacterial fish pathogen Aeromonas salmonicida. Escherichia coli carrying pJA8102-2 showed moderate resistance to tetracycline and low level resistance to minocycline. In addition, that carrying pBR322 derived from a tetracycline (tet) resistant gene of the Salmonella plasmid pSC101¹⁾ had the same resistance. The oxytetracycline resistance level cou1d not be induced after the E. coli carrying pJA8102-2 was exposed for 30 min to a culture containing a subinhibitory concentration of 1μg/ml of oxytetracycline. However, the oxytetracycline resistance level was induced by exposing it for 18h. The tet resistant gene of this 11.4 kilo base drug re-sistance plasmid was found to be located on a transposon. Restriction enzyme analysis and hybridization experiments indicated close relationship to the tet gene of pBR322. The proteins produced by this tet gene had molecular weights of 16.5, 17.5, 26, and 34 Kilo daltons (Kd). The 26 and 34 Kd of these proteins were similar to those produced by pSC101.²⁾