Bacteria use second-messenger molecules to adapt to their environment. Several second messengers, among them cyclic di-AMP (c-di-AMP), have been discovered and intensively studied. Interestingly, c-di-AMP is essential for growth of Gram-positive bacteria such as Bacillus subtilis, Listeria monocytogenes, and Staphylococcus aureus. Many studies demonstrated that perturbation of c-di-AMP metabolism affects the integrity of the bacterial cell envelope. Therefore, it has been assumed that the nucleotide is essential for proper cell envelope synthesis. In this Opinion paper, we propose that the cell envelope phenotypes caused by perturbations of c-di-AMP metabolism can be interpreted differently: c-di-AMP might indirectly control cell envelope integrity by modulating the turgor, a physical variable that needs to be tightly adjusted. We also discuss open questions related to c-di-AMP metabolism that need to be urgently addressed by future studies.

细菌利用第二信使分子来适应其环境。已经发现并深入研究了多个第二信使，其中包括循环二安培（c-di-AMP）。有趣的是，c-di-AMP对于革兰氏阳性细菌（如枯草芽孢杆菌，单核细胞增生性李斯特菌和金黄色葡萄球菌）的生长必不可少。许多研究表明，c-di-AMP代谢的紊乱会影响细菌细胞包膜的完整性。因此，已经假定核苷酸对于正确的细胞包膜合成是必不可少的。在本意见书中，我们建议对c-di-AMP代谢扰动引起的细胞包膜表型可以用不同的方式解释：c-di-AMP可能通过调节充盈性来间接控制细胞包膜的完整性，这是需要改变的物理变量。严格调整。我们还将讨论与c-di-AMP代谢有关的开放性问题，这些问题需要在以后的研究中紧急解决。