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 (嗜酸乳杆菌) 是一种具有代表性的益生菌，因其对人类和动物健康的有益作用而广泛应用于许多工业产品中。这种细菌暴露于制造工业产品的高温等恶劣环境中，但高温下的细胞产量相对较低。为了解决这个问题，我们开发了一个新的嗜酸乳杆菌通过适应性实验室进化 (ALE) 方法，在保留现有有益特性的同时，提高耐热性的应变。新开发的菌株，嗜酸乳杆菌EG008，将现有的热阻极限由65°C提高到75°C。此外，我们对野生型和 EG008 菌株进行了全基因组测序和比较基因组分析，以揭示提高耐热性的分子机制。有趣的是，只有两个单核苷酸多态性 (SNP) 与嗜酸乳杆菌野生型。我们确定这些 SNP 之一是非同义 SNP，能够通过第 435 个氨基酸从丝氨酸变为苏氨酸来改变 MurD 蛋白的结构。我们相信这些结果将直接有助于任何工业领域嗜酸乳杆菌被申请;被应用。此外，这些结果在理解极端条件下乳酸菌进化的分子机制方面向前迈进了一步。