CHARACTERIZATION OF A PROTEINACEOUS ANTIMICROBIAL PRODUCED BY LACTOBACILLUS-HELVETICUS CNRZ450

An antimicrobial substance which resembles a bacteriocin was identifie d in culture supernatant fluids of Lactobacillus helveticus strain CNR Z450. The bacteriocin was active against a narrow range of strains fro m closely related species of homofermentative lactobacilli, Its mode o f action appeared to be bacteriostatic, Partial purification of the ba cteriocin suggested that it was a complex protein with a mel. wt of be tween 30 and 50 kDa, although there is some evidence that the polypept ide monomer has a mel. wt of around 17 kDa. There was no evidence indi cating an extrachromosomal location for its genetic determinant. PCR g enerated an amplicon from total DNA from strain CNRZ450 using primers based on the helJ gene sequence. A fragment showing homology to this a mplicon was located in an EcoRI digest of total DNA from strain CNRZ45 0. The pattern obtained was different from that obtained with the helv eticin J producer strain NCFB481. It is possible, therefore, that the antimicrobial from strain CNRZ450 is related to helveticin J at the DN A sequence level although the physical properties of the two antimicro bials reveal several differences.