Patacq Clément, Chaudet Nicolas, Létisse Fabien
TBI, Université de Toulouse, INSA, INRAE, CNRS, UPS, Toulouse, France.
Sanofi Pasteur, Département de Bioprocédés R&D, Marcy-l'Etoile, France.
mSphere. 2020 Dec 23;5(6):e01132-20. doi: 10.1128/mSphere.01132-20.
Bacteria grow in constantly changing environments that can suddenly become completely depleted of essential nutrients. The stringent response, a rewiring of the cellular metabolism mediated by the alarmone (p)ppGpp, plays a crucial role in adjusting bacterial growth to the severity of the nutritional stress. The ability of (p)ppGpp to trigger a slowdown of cell growth or induce bacterial dormancy has been widely investigated. However, little is known about the role of (p)ppGpp in promoting growth recovery after severe growth inhibition. In this study, we performed a time-resolved analysis of (p)ppGpp metabolism in as it recovered from a sudden slowdown in growth. The results show that recovers by itself from the growth disruption provoked by the addition of serine hydroxamate, the serine analogue that we used to induce the stringent response. Growth inhibition was accompanied by a severe disturbance of metabolic activity and, more surprisingly, a transient overflow of valine and alanine. Our data also show that ppGpp is crucial for growth recovery since in the absence of ppGpp, 's growth recovery was slower. In contrast, an increased concentration of pppGpp was found to have no significant effect on growth recovery. Interestingly, the observed decrease in intracellular ppGpp levels in the recovery phase correlated with bacterial growth, and the main effect involved in the return to the basal level was identified by flux calculation as growth dilution. This report thus significantly expands our knowledge of (p)ppGpp metabolism in physiology. The capacity of microbes to resist and overcome environmental insults, known as resilience, allows them to survive in changing environments but also to resist antibiotic and biocide treatments and immune system responses. Although the role of the stringent response in bacterial resilience to nutritional stresses has been well studied, little is known about its importance in the ability of the bacteria to not just resist but also recover from these disturbances. To address this important question, we investigated growth disruption resilience in the model bacterium and its dependence on the stringent response alarmone (p)ppGpp by quantifying ppGpp and pppGpp levels as growth was disrupted and then recovered. Our findings may thus contribute to understanding how ppGpp improves 's resilience to nutritional stress and other environmental insults.
细菌生长在不断变化的环境中，这些环境可能会突然完全耗尽必需营养素。严格反应是一种由警报素（p）ppGpp介导的细胞代谢重排，在根据营养应激的严重程度调整细菌生长方面起着关键作用。（p）ppGpp触发细胞生长放缓或诱导细菌休眠的能力已得到广泛研究。然而，关于（p）ppGpp在严重生长抑制后促进生长恢复中的作用却知之甚少。在本研究中，我们对[细菌名称]从生长突然放缓中恢复时的（p）ppGpp代谢进行了时间分辨分析。结果表明，[细菌名称]可自行从添加丝氨酸羟肟酸（我们用于诱导严格反应的丝氨酸类似物）所引发的生长中断中恢复。生长抑制伴随着代谢活性的严重紊乱，更令人惊讶的是，缬氨酸和丙氨酸出现短暂溢出。我们的数据还表明，ppGpp对生长恢复至关重要，因为在没有ppGpp的情况下，[细菌名称]的生长恢复较慢。相比之下，发现pppGpp浓度增加对生长恢复没有显著影响。有趣的是，在恢复阶段观察到的细胞内ppGpp水平下降与细菌生长相关，通量计算确定恢复到基础水平的主要影响因素是生长稀释。因此，本报告显著扩展了我们对[细菌名称]生理学中（p）ppGpp代谢的认识。微生物抵抗和克服环境损伤的能力，即恢复力，使它们能够在不断变化的环境中生存，同时也能抵抗抗生素和杀菌剂处理以及免疫系统反应。尽管严格反应在细菌对营养应激的恢复力中的作用已得到充分研究，但对于其在细菌不仅抵抗而且从这些干扰中恢复的能力中的重要性却知之甚少。为了解决这个重要问题，我们通过在生长受到干扰然后恢复时定量ppGpp和pppGpp水平，研究了模式细菌[细菌名称]中的生长中断恢复力及其对严格反应警报素（p）ppGpp的依赖性。因此，我们的发现可能有助于理解ppGpp如何提高[细菌名称]对营养应激和其他环境损伤的恢复力。
