IDENTIFICATION AND PARTIAL CHARACTERIZATION OF TOCHICIN, A BACTERIOCIN PRODUCED BY BACILLUS-THURINGIENSIS SUBSP TOCHIGIENSIS

Bacillus thuringiensis subsp tochigiensis HD868 was identified as a ba cteriocin producer which exhibited a bactericidal effect against close ly related species, This bacteriocin designated as tochicin, was parti ally purified by 75% ammonium sulfate precipitation followed by subseq uent dialysis, This partially purified tochicin showed a narrow antiba cterial spectrum of activity against most of 20 typical B. thuringiens is strains and a strain of B. cereus, but not against other bacteria a nd yeasts tested, The antibacterial activity of tochicin on sensitive indicator cells disappeared completely by proteinase K treatment (1 mg ml(-1)), which indicates its proteinaceous nature, Tochicin was very stable throughout the range of pH 3.0-9.0 and was relatively heat-stab le at 90 degrees C, but bacteriocin activity was not detected after bo iling for 30 min, The relationship between cell growth and bacteriocin production was studied in a semi-defined medium, Tochicin activity wa s detected at the mid-log growth phase, reached the maximum at the ear ly stationary phase, but decreased after the stationary phase, Direct detection of tochicin activity on sodium dodecyl sulfate-polyacrylamid e gel suggested it has an apparent molecular mass of about 10.5 kDa, T ochicin exhibited a bactericidal activity against B. thuringiensis sub sp thompsoni HD522 in phosphate buffer (pH 7.0).