BACILLUS-SUBTILIS BS-107 AS AN ANTAGONIST OF POTATO BLACKLEG AND SOFT-ROT BACTERIA

Antimicrobial substances were produced by Bacillus subtilis BS 107 in a defined medium and isolated from culture filtrate by precipitation a t pH 2.5. Active fractions were extracted in ethyl acetate, acetone, a nd 80% ethanol and purified by thin-layer chromatography (TLC) on sili ca gel plates developed with an ethanol-water mixture (2:1, v/v). In e ach case, a band with a R-f of 0.75 formed an inhibitory zone when the TLC plates were placed in contact with agar seeded with test cultures of the Erwinia spp. The antibiotic was released into the culture medi um during early stages of growth of Bacillus subtilis BS 107 but highe r amounts were released in older cultures. The antibiotic was resistan t to the action of nucleases, proteases, and lipase. It was stable whe n autoclaved twice for 35 min at 3 atm (1 atm = 101.325 kPa) in acidic , neutral, and alkaline solutions. It remained active over the pH rang e of 1-14 during 1 month of observation and exhibited no loss of antim icrobial activity when stored at 4 degrees C for over 1 year. Bacillus subtilis BS 107 showed activity in vitro and in vivo against Erwinia carotovora subsp. atroseptica and Erwinia carotovora subsp. carotovora , the causal agents of potato blackleg and tuber soft rot. The applica tion of an antagonist or its antibiotic to cut potato tissues prevente d or reduced symptoms of the diseases. The antibiotic was active in vi tro against a broad spectrum of bacterial and fungal species.