Li Weixun, Yang Lan, Nan Wenlong, Lu Jing, Zhang Shuwen, Ujiroghene Obaroakpo Joy, Pang Xiaoyang, Lv Jiaping
Institute of Food Science and Technology, Chinese Academy of Agricultural Sciences, Beijing, 100193, China.
China Animal Health and Epidemiology Center, Qingdao, 266032, China.
Appl Microbiol Biotechnol. 2020 Sep;104(17):7631-7642. doi: 10.1007/s00253-020-10788-5. Epub 2020 Jul 27.
The probiotic efficacy and fermentative ability of Lactobacillus delbrueckii subsp. bulgaricus (L. bulgaricus), a widely used probiotic, is majorly affected by its acid tolerance. Here, we conducted whole-genome sequencing of the high acid-tolerant L. bulgaricus LJJ stored in the laboratory. Compared with the whole genome of low acid-tolerant strain L. bulgaricus ATCC11842, the results show that 16 candidate acid-tolerant genes may be involved in the regulation of the acid tolerance of L. bulgaricus LJJ. Association analysis of candidate acid-tolerant genes and acid-tolerant traits of different L. bulgaricus strains revealed that the three genes dapA, dapH, and lysC are the main reasons for the strong acid tolerance of L. bulgaricus LJJ. The results of real-time quantitative PCR (RT-qPCR) supported this conclusion. KEGG pathway analysis showed that these three acid-tolerant genes are involved in the synthesis of lysine; the synthesis of lysine may confer L. bulgaricus LJJ strong acid tolerance. This study successfully revealed the acid tolerance mechanism of L. bulgaricus LJJ and provides a theoretical basis for the subsequent selection of strains with high acid tolerance for improved probiotic functions. KEY POINTS: • Three genes are identified as acid-tolerant genes, respectively, lysC, dapA, and dapH. • LysC and dapA are the major key genes in the synthesis of lysine. • The synthesis of lysine may confer L. bulgaricus LJJ strong acid tolerance.
德氏乳杆菌保加利亚亚种（L. bulgaricus）是一种广泛使用的益生菌，其益生菌功效和发酵能力主要受其耐酸性影响。在此，我们对实验室保存的高耐酸性德氏乳杆菌LJJ进行了全基因组测序。与低耐酸性菌株德氏乳杆菌ATCC11842的全基因组相比，结果表明16个候选耐酸基因可能参与了德氏乳杆菌LJJ耐酸性的调控。对不同德氏乳杆菌菌株的候选耐酸基因与耐酸性状进行关联分析，发现dapA、dapH和lysC这三个基因是德氏乳杆菌LJJ耐酸性强的主要原因。实时定量PCR（RT-qPCR）结果支持了这一结论。KEGG通路分析表明，这三个耐酸基因参与赖氨酸的合成；赖氨酸的合成可能赋予德氏乳杆菌LJJ较强的耐酸性。本研究成功揭示了德氏乳杆菌LJJ的耐酸机制，为后续筛选高耐酸性菌株以改善益生菌功能提供了理论依据。要点：• 分别鉴定出三个耐酸基因，即lysC、dapA和dapH。• LysC和dapA是赖氨酸合成中的主要关键基因。• 赖氨酸的合成可能赋予德氏乳杆菌LJJ较强的耐酸性。
