Exposure of Escherichia coli cells in trypticase soy broth (TSB) for 30 min at 37°C to levels of a commercial nisin preparation yielding 0.1 or 1 mg/ml nisin prior to transfer into 0.6-0.8 M NaCl TSB increased growth at 37°C of statically incubated cultures for 15-25 h. Up to 81% of nisin added to the medium adsorbed to E. coli cells during the 30 min exposure. The commercial nisin preparation added to the medium at the same final concentrations immediately before E. coli was transferred into 0.6-0.8 M NaCI TSB had no effect on E. coli halotolerance. However, exposure of E. coli for 30 min to nisin preparation autoclaved at pH 10 to inactivate nisin, to 20 mg/ml NaCl, or to 20 mg/ml milk solids before being transferred into 0.8 M NaCl TSB enhanced E. coli growth in that medium.