J Biomed Nanotechnol. 2021 Mar 1;17(3):369-381. doi: 10.1166/jbn.2021.3035.
is an important industrial lactic acid bacteria, which can be used as a starter culture for fermented milk and meat products. Many strains can produce bacteriocins with broad-spectrum antibacterial properties, heat stability, and easy to be hydrolyzed by protease in the process of food fermentation and metabolism, and their potential as biopreservative starter culture in the preservation of fermented food has been recognized. However, the high salt environment in the food matrix can affect bacteriocin production. Hence, the objective of this research is to reveal how salt stress affects the production of bacteriocin and the expression of related genes in this strain by transcriptome sequencing and to further analyze possible regulatory mechanisms, to provide references for the use of bacteriocin as a natural biological preservative in salt-containing foods. The number of viable counts and the antibacterial activity of bacteriocin over the whole growth stages were determined under the stress of 0%, 2%, 3%, 4%, and 6% NaCl. When the strain was cultured at low nanoparticle NaCl concentration (2% or 3%), the growth of the experimental group had no significant difference compared with the control group; however, bacteriocin antibacterial activity increased significantly in the stable phase. When the target strain was cultured under 2% NaCl stress for 24 h, the antimicrobial activity reached the maximum. Subsequently, based on the transcriptome sequencing results obtained by Illumina HiSEq 2500 sequencing system, the differentially expressed genes under 0% and 2% NaCl stress were compared, and the enrichment pathways of these genes were analyzed. A total of 260 genes displayed significant differential expression induced by NaCl: Among them, 159 genes were significantly up-regulated, and 101 genes were down-regulated. Bioinformatic analysis revealed that differentially expressed genes related to bacteriocin synthesis were mainly enriched in bacterial secretion pathway, amino acid synthesis pathway, proteolytic enzyme regulation pathway, purine metabolism pathway, two-component reg- ulation pathway, etc. It is preliminarily speculated that nanoparticle NaCl stress can regulate the synthesis and release of bacteriocin by affecting the expression of secY and ftsY in the cell membrane secretion pathway. We also speculate that nanoparticle NaCl stress can provide raw materials for bacteriocin by affecting the expression levels of genes hisH, cysE, cysM, metB, metA, lysA, and argH in the amino acid synthesis pathway. In addition, our research signified that the expression levels of sat and rpoB in the purine metabolism pathway were up-regulated under nanoparticle NaCl stress, which is beneficial to provide energy for bacteriocin production. The results will be helpful to understand how salt stress regulates bacteriocin synthesis of . Furthermore, this study also provides guidance for using bacteriocin-producing strains as biocontrol bacteria in the salt-containing food matrix.
是一种重要的工业乳酸细菌，可用作发酵乳和肉制品的发酵剂。许多 菌株可以产生具有广谱抗菌特性、热稳定性且在食品发酵和代谢过程中容易被蛋白酶水解的细菌素，其作为发酵食品防腐剂的生物保鲜剂的潜力已得到认可。然而，食品基质中的高盐环境会影响细菌素的产生。因此，本研究旨在通过转录组测序揭示盐胁迫如何影响该菌株细菌素的产生和相关基因的表达，并进一步分析可能的调控机制，为细菌素作为含盐水食品中的天然生物防腐剂的应用提供参考。在 0%、2%、3%、4%和 6%NaCl 的胁迫下，测定了整个生长阶段的活菌数和细菌素的抑菌活性。当菌株在低纳米粒子 NaCl 浓度（2%或 3%）下培养时，实验组的生长与对照组相比没有显著差异；然而，在稳定期，细菌素的抑菌活性显著增加。当目标菌株在 2%NaCl 胁迫下培养 24 小时时，抑菌活性达到最大值。随后，基于 Illumina HiSEq 2500 测序系统获得的转录组测序结果，比较了 0%和 2%NaCl 胁迫下差异表达的基因，并分析了这些基因的富集途径。共筛选出 260 个受 NaCl 诱导的差异表达基因：其中 159 个基因显著上调，101 个基因下调。生物信息学分析表明，与细菌素合成相关的差异表达基因主要富集在细菌分泌途径、氨基酸合成途径、蛋白酶调控途径、嘌呤代谢途径、双组分调控途径等。初步推测纳米粒子 NaCl 胁迫可以通过影响细胞膜分泌途径中 secY 和 ftsY 的表达来调节细菌素的合成和释放。我们还推测，纳米粒子 NaCl 胁迫可以通过影响氨基酸合成途径中 hisH、cysE、cysM、metB、metA、lysA 和 argH 等基因的表达水平，为细菌素提供原料。此外，我们的研究表明，嘌呤代谢途径中 sat 和 rpoB 的表达水平在纳米粒子 NaCl 胁迫下上调，有利于为细菌素的产生提供能量。研究结果将有助于了解盐胁迫如何调节 细菌素的合成。此外，本研究还为在含盐水食品基质中使用产细菌素菌株作为生物防治细菌提供了指导。
