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乳球菌乳亚种 F44 和 G423 的基因组和转录组:对适应酸性环境的深入了解。

The genome and transcriptome of Lactococcus lactis ssp. lactis F44 and G423: Insights into adaptation to the acidic environment.

机构信息

Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China; Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjian 300072, P.R. China.

Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjian 300072, P.R. China.

出版信息

J Dairy Sci. 2019 Feb;102(2):1044-1058. doi: 10.3168/jds.2018-14882. Epub 2018 Dec 26.

Abstract

Nisin, as a common green (environmentally friendly), nontoxic antibacterial peptide secreted by Lactococcus lactis, is widely used to prevent the decomposition of meat and dairy products and maintains relatively high stability at low pH. However, the growth of Lc. lactis is frequently inhibited by high lactic acid concentrations produced during fermentation. This phenomenon has become a great challenge in enhancing the nisin yield for this strain. Here, the shuffled strain G423 that could survive on a solid plate at pH 3.7 was generated through protoplast fusion-mediated genome shuffling. The nisin titer of G423 peaked at 4,543 IU/mL, which was 59.9% higher than that of the same batch of the initial strain Lc. lactis F44. The whole genome comparisons between G423 and F44 indicated that 6 large fragments (86,725 bp) were inserted in G423 compared with that of Lc. lactis F44. Transcriptome data revealed that 4 novel noncoding transcripts, and the significantly upregulated genes were involved in multiple processes in G423. In particular, the expression of genes involved in cell wall and membrane biosynthesis was obviously perturbed under acidic stress. Quantitative real-time PCR analysis showed that the transcription of noncoding small RNA NC-1 increased by 2.35-fold at pH 3.0 compared with that of the control (pH 7.0). Overexpression assays indicated that small RNA NC-1 could significantly enhance the acid tolerance and nisin production of G423 and F44. Our work provided new insights into the sophisticated genetic mechanisms involved in Lc. lactis in an acidic environment, which might elucidate its potential application in food and dairy industries.

摘要

乳链菌肽是乳酸乳球菌分泌的一种常见的绿色(环保)、无毒抗菌肽,常用于防止肉类和乳制品的分解,并且在低 pH 值下保持相对较高的稳定性。然而,在发酵过程中产生的高浓度乳酸经常会抑制乳酸乳球菌的生长。这一现象成为提高该菌株乳链菌肽产量的一大挑战。在这里,通过原生质体融合介导的基因组改组,产生了一种能够在 pH 3.7 的固体平板上存活的改组菌株 G423。G423 的乳链菌肽产量峰值达到 4,543 IU/mL,比同一批初始菌株 Lc. lactis F44 高 59.9%。G423 与 F44 之间的全基因组比较表明,与 Lc. lactis F44 相比,G423 中有 6 个大片段(86725 bp)插入。转录组数据显示,G423 中有 4 个新的非编码转录本,并且显著上调的基因参与了 G423 中的多个过程。特别是,在酸性胁迫下,与细胞壁和膜生物合成相关的基因表达明显受到干扰。定量实时 PCR 分析表明,与对照(pH 7.0)相比,在 pH 3.0 时非编码小 RNA NC-1 的转录增加了 2.35 倍。过表达实验表明,小 RNA NC-1 可以显著提高 G423 和 F44 的耐酸性和乳链菌肽产量。我们的工作为乳酸乳球菌在酸性环境中的复杂遗传机制提供了新的见解,这可能阐明其在食品和乳制品行业的潜在应用。

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