Department of Molecular Genetics, University of Groningen, Groningen Biomolecular Sciences and Biotechnology Institute, Groningen, the Netherlands.
Department of Molecular Genetics, University of Groningen, Groningen Biomolecular Sciences and Biotechnology Institute, Groningen, the Netherlands
Appl Environ Microbiol. 2020 Apr 1;86(8). doi: 10.1128/AEM.02937-19.
subsp. MG1363 is a model for the lactic acid bacteria (LAB) used in the dairy industry. The proteolytic system, consisting of a proteinase, several peptide and amino acid uptake systems, and a host of intracellular peptidases, plays a vital role in nitrogen metabolism and is of eminent importance for flavor formation in dairy products. The dipeptidase PepV functions in the last stages of proteolysis. A link between nitrogen metabolism and peptidoglycan (PG) biosynthesis was underlined by the finding that deletion of the dipeptidase gene (creating strain MGΔ) resulted in a prolonged lag phase when the mutant strain was grown with a high concentration of glycine. In addition, most MGΔ cells lyse and have serious defects in their shape. This phenotype is due to a shortage of alanine, since adding alanine can rescue the growth and shape defects. Strain MGΔ is more resistant to vancomycin, an antibiotic targeting peptidoglycan d-Ala-d-Ala ends, which confirmed that MGΔ has an abnormal PG composition. A mutant of MGΔ was obtained in which growth inhibition and cell shape defects were alleviated. Genome sequencing showed that this mutant has a single point mutation in the gene, resulting in an arginine residue at position 218 in the DNA-binding motif of CodY being replaced by a cysteine residue. Thus, this strain was named MGΔ Transcriptome sequencing (RNA-seq) data revealed a dramatic derepression in peptide uptake and amino acid utilization in MGΔ A model of the connections among PepV activity, CodY regulation, and PG synthesis of is proposed. Precise control of peptidoglycan synthesis is essential in Gram-positive bacteria for maintaining cell shape and integrity as well as resisting stresses. Although neither the dipeptidase PepV nor alanine is essential for MG1363, adequate availability of either ensures proper cell wall synthesis. We broaden the knowledge about the dipeptidase PepV, which acts as a linker between nitrogen metabolism and cell wall synthesis in .
亚群。MG1363 是用于乳制品行业的乳酸菌 (LAB) 的模型。由蛋白酶、几种肽和氨基酸摄取系统以及一系列细胞内肽酶组成的蛋白水解系统在氮代谢中起着至关重要的作用，对乳制品的风味形成具有重要意义。二肽酶 PepV 在蛋白水解的最后阶段发挥作用。氮代谢和肽聚糖 (PG) 生物合成之间的联系通过以下发现得到强调：删除二肽酶基因（创建菌株 MGΔ）会导致突变菌株在高浓度甘氨酸存在下生长时延长迟滞期。此外，大多数 MGΔ 细胞裂解并且形状严重缺陷。这种表型是由于丙氨酸短缺引起的，因为添加丙氨酸可以挽救生长和形状缺陷。菌株 MGΔ 对万古霉素的抗性更强，万古霉素是一种针对肽聚糖 d-Ala-d-Ala 末端的抗生素，这证实了 MGΔ 具有异常的 PG 组成。获得了一种减轻生长抑制和细胞形状缺陷的 MGΔ 突变体。基因组测序表明，该突变体在 基因中有一个单点突变，导致 CodY DNA 结合基序中第 218 位的精氨酸残基被半胱氨酸残基取代。因此，该菌株被命名为 MGΔ。转录组测序 (RNA-seq) 数据显示，MGΔ 中肽摄取和氨基酸利用的显著去阻遏。提出了 PepV 活性、CodY 调节和 PG 合成之间关系的模型。在革兰氏阳性菌中，精确控制肽聚糖合成对于维持细胞形状和完整性以及抵抗应激至关重要。尽管二肽酶 PepV 和丙氨酸对于 MG1363 都不是必需的，但两者的充分可用性都确保了适当的细胞壁合成。我们拓宽了关于二肽酶 PepV 的知识，它在 中作为氮代谢和细胞壁合成之间的连接物发挥作用。
