Morawska Luiza P, Kuipers Oscar P
Molecular Genetics Group, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747 AG Groningen, Netherlands.
Microlife. 2022 Jun 29;3:uqac010. doi: 10.1093/femsml/uqac010. eCollection 2022.
Bacterial communities exposed to rapid changes in their habitat encounter different forms of stress. Fluctuating conditions of the microenvironment drive microorganisms to develop several stress responses to sustain growth and division, like altering gene expression and changing the cell's physiology. It is commonly known that these protection systems may give rise to differently adapted subpopulations and indirectly impact bacterial susceptibility to antimicrobials. This study focuses on the adaptation of a soil-dwelling bacterium, , to sudden osmotic changes, including transient and sustained osmotic upshift. Here, we demonstrate that physiological changes caused by pre-exposure to osmotic stress facilitate ' entry into a quiescent state, helping them survive when exposed to a lethal antibiotic concentration. We show that the adaptation to transient osmotic upshift with 0.6 M NaCl causes decreased metabolic rates and lowered antibiotic-mediated ROS production when cells were exposed to the aminoglycoside antibiotic kanamycin. Using a microfluidic platform combined with time-lapse microscopy, we followed the uptake of fluorescently labelled kanamycin and examined the metabolic activity of differently preadapted populations at a single-cell level. The microfluidics data revealed that under the conditions tested, escapes from the bactericidal activity of kanamycin by entering into a nongrowing dormant state. Combining single-cell studies and population-wide analysis of differently preadapted cultures, we demonstrate that kanamycin-tolerant cells are entrapped in a viable but nonculturable (VBNC) state.
暴露于栖息地快速变化的细菌群落会遇到不同形式的压力。微环境的波动条件促使微生物产生多种应激反应以维持生长和分裂，比如改变基因表达和细胞生理状态。众所周知，这些保护系统可能会产生适应性不同的亚群，并间接影响细菌对抗菌药物的敏感性。本研究聚焦于一种土壤细菌对突然的渗透压变化的适应性，包括短暂和持续的渗透压升高。在此，我们证明，预先暴露于渗透压应激所引起的生理变化有助于细菌进入静止状态，使它们在接触致死性抗生素浓度时得以存活。我们表明，用0.6 M NaCl对短暂渗透压升高进行适应性处理后，当细胞接触氨基糖苷类抗生素卡那霉素时，代谢率降低，抗生素介导的活性氧生成减少。使用微流控平台结合延时显微镜，我们跟踪了荧光标记的卡那霉素的摄取情况，并在单细胞水平上检测了不同预先适应群体的代谢活性。微流控数据显示，在所测试的条件下，细菌通过进入不生长的休眠状态而逃避卡那霉素的杀菌活性。结合单细胞研究和对不同预先适应培养物的全群体分析，我们证明耐卡那霉素的细菌细胞被困在活的但不可培养（VBNC）状态。
