Lactostrepcins - acid bacteriocins produced by lactic streptococci

Abstract

Summary: All 47 non-nisin producing strains ofStreptococcus lactisand 12/13 strains ofStr. lactissubsp.diacetylactisexamined produced bacteriocins, for which the term lactostrepcins is suggested. Seven strains ofStr. cremorisexamined produced no bacteriocins active against 3 lactic streptococci strains used as indicators. The strains examined were divided into 3 groups: I, those producing lactostrepcins active against only one streptomycin resistant mutant ofStr. lactis60 indicator strain; II, those producing lactostrepcins active against all 3 indicator strains; III, those not producing lactostrepcins active against the indicator strains employed. The lactostrepcins were sensitive to various proteolytic enzymes and to phospholipase D, but retained full or partial activity after dialysis. Most of the bacteriocins studied were fully active only within the pH range 4·2–5·0 and were reversibly inactivated at pH 7·0 or 8·0. Results suggested occurrence of 4 different lactostrepcins. The lactostrepcins produced by all group I strains were the same, but there were differences among the lactostrepcins produced by group II strains. Lactostrepcins killed some β-haemolytic streptococci and some strains ofLactobacillus helveticus. One of the lactostrepcins was also active against certainLeuconostocstrains, but not against otherLeuconostocstrains, nor againstL. helveticusor other Gram-positive bacteria.