Data_Sheet_1_Complete Genome Sequence of the Newly Developed Lactobacillus acidophilus Strain With Improved Thermal Adaptability.docx

Lactobacillus acidophilus (L. acidophilus) is a representative probiotic and is widely used in many industrial products for its beneficial effects on human and animal health. This bacterium is exposed to harsh environments such as high temperatures for manufacturing industrial products, but cell yield under high temperatures is relatively low. To resolve this issue, we developed a new L. acidophilus strain with improved heat resistance while retaining the existing beneficial properties through the adaptive laboratory evolution (ALE) method. The newly developed strain, L. acidophilus EG008, has improved the existing limit of thermal resistance from 65°C to 75°C. Furthermore, we performed whole-genome sequencing and comparative genome analysis of wild-type and EG008 strains to unravel the molecular mechanism of improved heat resistance. Interestingly, only two single-nucleotide polymorphisms (SNPs) were different compared to the L. acidophilus wild-type. We identified that one of these SNPs is a non-synonymous SNP capable of altering the structure of MurD protein through the 435th amino acid change from serine to threonine. We believe that these results will directly contribute to any industrial field where L. acidophilus is applied. In addition, these results make a step forward in understanding the molecular mechanisms of lactic acid bacteria evolution under extreme conditions.

嗜酸乳杆菌（Lactobacillus acidophilus，简称L. acidophilus）是一类典型的益生菌，因其对人类与动物健康的有益功效，被广泛应用于各类工业产品中。该菌株在工业生产过程中会遭遇高温等严苛环境，但高温条件下的菌体产量相对较低。为解决这一问题，本研究通过适应性实验室进化（adaptive laboratory evolution，ALE）技术，在保留其固有有益特性的前提下，开发出一株耐热性能提升的新型L. acidophilus菌株。新开发的菌株L. acidophilus EG008将现有耐热极限从65℃提升至75℃。为阐明该菌株耐热性提升的分子机制，本研究对野生型菌株与EG008菌株开展了全基因组测序与比较基因组分析。值得注意的是，与野生型L. acidophilus相比，二者仅存在两处单核苷酸多态性（single-nucleotide polymorphisms，SNPs）差异。本研究确认其中一处为非同义单核苷酸多态性，该变异可通过将第435位氨基酸由丝氨酸替换为苏氨酸，改变MurD蛋白的空间结构。本研究结果可直接为所有应用L. acidophilus的工业领域提供理论与技术支撑，同时也为解析极端环境下乳酸菌进化的分子机制迈出了关键一步。