揭示嗜热链球菌突变体半乳糖阳性表型背后的遗传基础和代谢线路重构

IF 6.1 1区 生物学 Q1 MICROBIOLOGY Microbiological research Pub Date : 2024-09-11 DOI:10.1016/j.micres.2024.127894
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引用次数: 0

摘要

嗜热链球菌(S. thermophilus)是乳制品发酵中广泛使用的启动培养物,但大多数菌株都是半乳糖阴性的,只能代谢乳糖水解产生的葡萄糖。在本研究中,我们旨在揭示嗜热杆菌突变菌株 IMAU10636 获得稳定的半乳糖阳性(Gal+)表型的机制。通过用诱变剂 N-甲基-N-亚硝基-N-亚硝基胍处理野生型菌株,我们成功分离出了 Gal+ 突变体嗜热菌 IMAU10636Y。酶活性比较试验显示,与野生型相比,突变体具有更高的β-半乳糖苷酶和半乳激酶活性,但葡萄糖激酶和丙酮酸激酶活性较低。高效液相色谱分析证实,突变体利用乳糖和半乳糖的能力增强,导致葡萄糖分泌增加。基因组学和转录组学的综合分析使我们对潜在的遗传和代谢机制有了更深入的了解。我们发现,突变体中糖酵解/Leloir 途径的代谢调控网络发生了改变,这可能是由于 galR-galK 基因间区域的基因表达上调所致。这可能导致 RNA 聚合酶的结合和 gal 操作子的转录增加,最终促进了 Gal+ 表型的形成。此外,我们还发现编码 LacI 家族转录抑制因子的 scrR 基因发生了突变,这也导致了 Gal+ 表型的形成。这些发现为嗜热菌获得半乳糖代谢能力的代谢重构和调控机制提供了新的视角。这些知识可为乳制品应用中具有理想发酵特性的 Gal+ 菌株的工程和选择策略提供参考。
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Unveiling the genetic basis and metabolic rewiring behind the galactose-positive phenotype in a Streptococcus thermophilus mutant

Streptococcus thermophilus (S. thermophilus) is a widely used starter culture in dairy fermentation, but most strains are galactose-negative and only metabolize glucose from lactose hydrolysis. In this study, we aimed to uncover the mechanisms underlying the acquisition of a stable galactose-positive (Gal+) phenotype in a mutant strain of S. thermophilus IMAU10636. By treating the wild-type strain with the mutagenic agent N-methyl-N-nitro-N-nitrosoguanidine, we successfully isolated a Gal+ mutant, S. thermophilus IMAU10636Y. Comparative enzyme activity assays revealed that the mutant exhibited higher β-galactosidase and galactokinase activities, but lower glucokinase and pyruvate kinase activities compared to the wild-type. High-performance liquid chromatography analysis confirmed the mutant’s enhanced ability to utilize lactose and galactose, leading to increased glucose secretion. Integrated genome and transcriptomics analyses provided deeper insights into the underlying genetic and metabolic mechanisms. We found that the metabolism regulatory network of the glycolysis / Leloir pathway was altered in the mutant, possibly due to the upregulation of the gene expression in the galR-galK intergenic region. This likely led to increased RNA polymerase binding and transcription of the gal operon, ultimately promoting the Gal+ phenotype. Additionally, we identified a mutation in the scrR gene, encoding a LacI family transcriptional repressor, which also contributed to the Gal+ phenotype. These findings offer new perspectives on the metabolic rewiring and regulatory mechanisms that enable S. thermophilus to acquire the ability to metabolize galactose. This knowledge can inform strategies for engineering and selecting Gal+ strains with desirable fermentation characteristics for dairy applications.

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来源期刊
Microbiological research
Microbiological research 生物-微生物学
CiteScore
10.90
自引率
6.00%
发文量
249
审稿时长
29 days
期刊介绍: Microbiological Research is devoted to publishing reports on prokaryotic and eukaryotic microorganisms such as yeasts, fungi, bacteria, archaea, and protozoa. Research on interactions between pathogenic microorganisms and their environment or hosts are also covered.
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