The human pathogen Listeria monocytogenes synthesizes and degrades c-di-AMP using the diadenylate cyclase CdaA and the phosphodiesterases PdeA and PgpH respectively. c-di-AMP is essential because it prevents the uncontrolled uptake of osmolytes. Here, we studied the phenotypes of cdaA, pdeA, pgpH and pdeA pgpH mutants with defects in c-di-AMP metabolism and characterized suppressor mutants restoring their growth defects. The characterization of the pdeA pgpH mutant revealed that the bacteria show growth defects in defined medium, a phenotype that is invariably suppressed by mutations in cdaA. The previously reported growth defect of the cdaA mutant in rich medium is suppressed by mutations that osmotically stabilize the c-di-AMP-free strain. We also found that the cdaA mutant has an increased sensitivity against isoleucine. The isoleucine-dependent growth inhibition of the cdaA mutant is suppressed by codY mutations that likely reduce the DNA-binding activity of encoded CodY variants. Moreover, the characterization of the cdaA suppressor mutants revealed that the Opp oligopeptide transport system is involved in the uptake of the antibiotic fosfomycin. In conclusion, the suppressor analysis corroborates a key function of c-di-AMP in controlling osmolyte homeostasis in L. monocytogenes.

中文翻译：

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单核细胞增生李斯特菌对 c-di-AMP 代谢扰动的适应巩固了其在渗透适应中的作用并确定了磷霉素摄取系统

人类病原体单核细胞增生李斯特菌分别使用二腺苷酸环化酶 CdaA 和磷酸二酯酶 PdeA 和 PgpH 合成和降解 c-di-AMP。c-di-AMP 是必不可少的，因为它可以防止不受控制地吸收渗透质。在这里，我们研究了 c-di-AMP 代谢缺陷的cdaA、pdeA、pgpH和pdeA pgpH突变体的表型以及恢复其生长缺陷的抑制突变体。pdeA pgpH突变体的表征表明，细菌在确定的培养基中表现出生长缺陷，这种表型总是受到cdaA突变的抑制。先前报道的cdaA的生长缺陷富培养基中的突变体受到渗透稳定无 c-di-AMP 菌株的突变的抑制。我们还发现cdaA突变体对异亮氨酸的敏感性增加。cdaA突变体的异亮氨酸依赖性生长抑制受到可能降低编码 CodY 变体的 DNA 结合活性的codY突变的抑制。此外，对cdaA抑制突变体的表征表明 Opp 寡肽转运系统参与抗生素磷霉素的摄取。总之，抑制分析证实了 c-di-AMP 在控制L中渗透压稳态的关键功能。单核细胞增多症。