(p)ppGpp is a nucleotide alarmone that controls bacterial response to nutrient deprivation. Since elevated (p)ppGpp levels confer mecillinam resistance and are essential for broad-spectrum β-lactam resistance as mediated by the β-lactam-insensitive transpeptidase YcbB (LdtD), we hypothesized that (p)ppGpp might affect cell wall peptidoglycan metabolism. Here we report that (p)ppGpp-dependent β-lactam resistance does not rely on any modification of peptidoglycan metabolism, as established by analysis of Escherichia coli peptidoglycan structure using high-resolution mass spectrometry. Amino acid substitutions in the β or β’ RNA polymerase (RNAP) subunits, alone or in combination with the CRISPR interference-mediated downregulation of three of seven ribosomal RNA operons, were sufficient for resistance, although β-lactams have no known impact on the RNAP or ribosomes. This implies that modifications of RNAP and ribosome functions are critical to prevent downstream effects of the inactivation of peptidoglycan transpeptidases by β-lactams.

(p)ppGpp 是一种核苷酸报警素，可控制细菌对营养缺乏的反应。由于 (p)ppGpp 水平升高会产生美西林耐药性，并且对于由 β-内酰胺不敏感转肽酶 YcbB (LdtD) 介导的广谱 β-内酰胺耐药性至关重要，因此我们假设 (p)ppGpp 可能会影响细胞壁肽聚糖代谢。在这里，我们报告说，(p)ppGpp 依赖性 β-内酰胺耐药性不依赖于肽聚糖代谢的任何改变，正如使用高分辨率质谱分析大肠杆菌肽聚糖结构所证实的那样。β 或 β' RNA 聚合酶 (RNAP) 亚基中的氨基酸取代，单独或与 CRISPR 干扰介导的七个核糖体 RNA 操纵子中的三个下调相结合，足以产生耐药性，尽管 β-内酰胺对耐药性没有已知的影响。 RNAP 或核糖体。这意味着 RNAP 和核糖体功能的修饰对于防止 β-内酰胺导致肽聚糖转肽酶失活的下游效应至关重要。