AUTHOR=Vukotic Goran , Mirkovic Nemanja , Jovcic Branko , Miljkovic Marija , Strahinic Ivana , Fira Djordje , Radulovic Zorica , Kojic Milan 

TITLE=Proteinase PrtP impairs lactococcin LcnB activity in Lactococcus lactis BGMN1-501: new insights into bacteriocin regulation

JOURNAL=Frontiers in Microbiology

VOLUME=6

YEAR=2015

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2015.00092

DOI=10.3389/fmicb.2015.00092

ISSN=1664-302X

ABSTRACT=<p>Proteinases and bacteriocins are of great importance to the dairy industry, but their interactions have not been studied so far. <italic>Lactococcus lactis</italic> subsp. <italic>lactis</italic> BGMN1-5 is a natural isolate from homemade semi-hard cheese which produces two bacteriocins (Lactococcin B and LsbB), as well as proteinase PrtP. A medium-dependent increase in the bacteriocin LcnB activity of <italic>L. lactis</italic> BGMN1-501, a derivate of <italic>L. lactis</italic> subsp. <italic>lactis</italic> BGMN1-5, was shown to be accompanied by a decrease in its promoter activity. A similar effect of media components on gene expression was reported for proteinase PrtP, whose gene is co-localized on the same plasmid as the <italic>lcnB</italic> gene. Thus, the PrtP-LcnB interplay was investigated. Single gene knockout mutants were constructed with disrupted <italic>prtP</italic> or <italic>lcnB</italic> genes. PrtP<sup>-</sup> mutants showed higher bacteriocin activity that had lost its growth medium dependence, which was in contrast to the original strain. When LcnB from this mutant was combined with proteinase from the LcnB<sup>-</sup> mutant <italic>in vitro</italic>, its activity was rendered to the original level, suggesting that proteinase reduces bacteriocin activity. We propose a new model of medium dependent expression of these genes with regard to the effects of their interaction <italic>in vivo</italic>.</p>