Abstract
Certain probiotic species of lactic acid bacteria, especially Lactobacillus plantarum, regulate bacteriocin synthesis through quorum sensing (QS) systems. In this study, we aimed to investigate the luxS-mediated molecular mechanisms of QS during bacteriocin synthesis by L. plantarum KLDS1.0391. In the absence of luxS, the ‘spot-on-the-lawn’ method showed that the bacteriocin production by L. plantarum KLDS1.0391 significantly decreased upon co-cultivation with L. helveticus KLDS1.9207 (P < 0.01) but did not change significantly when mono-cultivated. Furthermore, liquid chromatography-electrospray ionization tandem mass spectrometry analysis showed that, as a response to luxS deletion, L. plantarum KLDS1.0391 altered the expression level of proteins involved in carbohydrate metabolism, amino acid metabolism, fatty acid synthesis and metabolism, and the two-component regulatory system. In particular, the sensor histidine kinase AgrC (from the two-component system, LytTR family) was expressed differently between the luxS mutant and the wild-type strain during co-cultivation, whereas no significant differences in proteins related to bacteriocin biosynthesis were found upon mono-cultivation. In summary, we found that the production of bacteriocin was regulated by carbohydrate metabolism, amino acid metabolism, fatty acid synthesis and metabolism, and the two-component regulatory system. Furthermore, our results demonstrate the role of luxS-mediated molecular mechanisms in bacteriocin production.
Highlights
Lactic acid bacteria (LAB) produce antimicrobial metabolites and have been traditionally used as starter cultures for different fermented foods, medicine, and feed
The quorum sensing (QS) system comprises two components: the first consists of signalling molecules, which are referred to as autoinducers (AIs, including AI-1 and AI-2) or AI peptides (AIP); the second is the two-component regulatory system, which comprises the membrane-located histidine protein kinase that monitors one or more environmental factors, as well as the cytoplasmic response regulator that modulates the expression of specific genes
We found that the bacteriocin production by L. plantarum KLDS1.0391 was markedly increased (P < 0.01) when co-cultivated with L. helveticus KLDS1.920716, a strain that does not produce bacteriocins
Summary
Lactic acid bacteria (LAB) produce antimicrobial metabolites and have been traditionally used as starter cultures for different fermented foods, medicine, and feed. Through adopting co-culture conditions or by constructing a two-component or AI-2/luxS mutant strain, previous studies[6,7] have demonstrated that bacteriocin production is regulated via the QS pathway. We found that the bacteriocin production by L. plantarum KLDS1.0391 was markedly increased (P < 0.01) when co-cultivated with L. helveticus KLDS1.920716, a strain that does not produce bacteriocins. In our previous research, we constructed a luxS mutant strain of L. plantarum KLDS1.0391 by homologous recombination (manuscript submitted, under review) to illustrate the effect of luxS on bacteriocin production in mono-cultivation and co-cultivation with L. helveticus KLDS1.9207. We further aimed to investigate luxS-mediated molecular mechanisms in the bacteriocin synthesis by L. plantarum KLDS1.0391 upon co-cultivation with L. helveticus KLDS1.9207 and during mono-cultivation, using a label-free quantitative shotgun proteomics strategy
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