Cyclic di-AMP (c-di-AMP) is an essential and ubiquitous second messenger among bacteria. c-di-AMP regulates many cellular pathways through direct binding to several molecular targets in bacterial cells. c-di-AMP depletion is well known to destabilize the bacterial cell wall, resulting in increased bacteriolysis and enhanced susceptibility to cell wall targeting antibiotics. Using the human pathogen Listeria monocytogenes as a model, we found that c-di-AMP accumulation also impaired cell envelope integrity. An L. monocytogenes mutant deleted for c-di-AMP phosphodiesterases (pdeA pgpH mutant) exhibited a 4-fold increase in c-di-AMP levels and several cell wall defects. For instance, the pdeA pgpH mutant was defective for the synthesis of peptidoglycan muropeptides and was susceptible to cell wall-targeting antimicrobials. Among different muropeptide precursors, we found that the pdeA pgpH strain was particularly impaired in the synthesis of d-Ala–d-Ala, which is required to complete the pentapeptide stem associated with UDP–N-acetylmuramic acid (MurNAc). This was consistent with an increased sensitivity to d-cycloserine, which inhibits the d-alanine branch of peptidoglycan synthesis. Finally, upon examining d-Ala:d-Ala ligase (Ddl), which catalyzes the conversion of d-Ala to d-Ala–d-Ala, we found that its activity was activated by K⁺. Based on previous reports that c-di-AMP inhibits K⁺ uptake, we propose that c-di-AMP accumulation impairs peptidoglycan synthesis, partially through the deprivation of cytoplasmic K⁺ levels, which are required for cell wall-synthetic enzymes.

中文翻译：

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c-di-AMP积累会损害单核细胞增生性李斯特菌中的肽合成

环二AMP（c-di-AMP）是细菌中必不可少的普遍信使。c-di-AMP通过直接结合细菌细胞中的多个分子靶标来调节许多细胞途径。众所周知，c-di-AMP的消耗会破坏细菌细胞壁的稳定性，导致增加的溶菌作用和对细胞壁靶向抗生素的敏感性增加。使用人类病原体单核细胞增生李斯特氏菌为模型，我们发现c-di-AMP积累也损害了细胞包膜的完整性。一个单增李斯特菌突变体对c-二-AMP磷酸二酯酶（删除PDEA PGPH突变体）表现出的c-二AMP水平和几个细胞壁缺陷的增加4倍。例如，pdeA pgpH该突变体对于肽聚糖多肽的合成是有缺陷的，并且易于靶向细胞壁的抗微生物剂。在不同的多肽前体中，我们发现pdeA pgpH菌株在d- Ala– d- Ala的合成中特别受损，而d- Ala– d -Ala的合成是完成与UDP– N –乙酰基尿酸（MurNAc）相关的五肽茎所必需的。这与对d-环丝氨酸的敏感性增加相一致，其抑制了肽聚糖合成的d-丙氨酸分支。最后，在检查d -Ala时：d -Ala连接酶（Ddl），它催化d -Ala转化为d-Ala– d -Ala，我们发现其活性被K ⁺激活。根据以前的报道，c-di-AMP抑制K ⁺摄取，我们建议c-di-AMP积累会部分剥夺细胞壁合成酶所需的胞质K ⁺水平，从而损害肽聚糖的合成。