Full Length Research Paper
Abstract
The biosynthesis of class II bacteriocins is frequently regulated by a quorum-sensing regulatory mechanism meditated by autoinducing peptide. Here, it was preliminarily confirmed that bacteriocin production by Lactobacillus pentosus 31-1 was controlled by a quorum sensing (QS) system meditated by peptide signal molecules in the cell-free supernatant (CFS). Effects of the growth medium and inoculums size on bacteriocin producing in L. pentosus 31-1 were investigated. Bacteriocin production could be detected even when L. pentosus 31-1 was diluted 108-fold in MRS broth and incubated at 37°C for 24 h. However, by dilution of the culture 200-fold or more in skim milk medium, no bacteriocin activity could be detected after 60 h of incubation. Bacteriocin production could be switched on in these cultures after the addition of CFS from a bacteriocin-producing culture, and the active components in the CFS were shown to be peptides in nature. FII-22, one of the fractions purified from the CFS was identified as the putative inducing peptide (IP). Regulation of bacteriocin production in L. pentosus 31-1 by FII-22 was affected by the additional time and amount. The optimal induction of bacteriocin production effect was obtained by addition of 0.5 µg/ml (final concentration) FII-22 to the culture after 8 h of incubation. This study provided a novel perspective on screening for QS regulated class II bacteriocin producing lactic acid bacteria. This study may assist in a deeper understanding of how QS works on regulation of class II bacteriocin production.
Key words: Quorum sensing, class II bacteriocin, Lactobacillus pentosus, inducing peptide, skim milk medium.
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