Isolation and Characterization of a Bacteriocin Produced by Pseudomonas solanacearum

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Abstract
Strain B1, an avirulent non-slime-producing variant of P. solanacearum K60, had greater bacteriocinogenic activity than did strain K60 both in liquid and on solid medium. The bacteriocin synthesized by strain B1 inhibited the growth of 43 of 51 P. solanacearum strains tested. It had no effect on strain B1, strain K60, or selected strains from 10 other bacterial species. Although the optimal growth temperature for strain B1 was 32.degree.C, the temperature most favorable for bacteriocin production was 30.degree. C. Bacteriocin titer could be increased by short exposure to ultraviolet light but not by chemical inducing agents. The bacteriocin produced by strain B1 was purified from the culture supernatant by (NH4)2SO4 precipitation, anion exchange chromatography, membrane ultrafiltration and preparative electrophoresis. Purified bacteriocin, being non-sedimentable, thermolabile and sensitive to proteolytic enzymes, resembled the S-type bacteriocins produced by P. aeuginosa. As determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the purified bacteriocin had a MW of about 65,000. It was insensitive to chloroform, nucleases and phospholipase. Although the bacteriocin present in culture supernatant was stable for 3 mo. at 4.degree. C, the activity of purified bacteriocin declined rapidly under a variety of storage conditions. Maximum pH stability was between 6-8.

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