Departamento de Microbiología, Facultad de Ciencias Biológicas, Universidad de Concepción, P.O. Box 160-C, Concepción, Chile.
Curr Microbiol. 2019 Dec;76(12):1435-1442. doi: 10.1007/s00284-019-01763-z. Epub 2019 Sep 7.
Bacteria under stress increase the proportion of dormant cells to ensure their survival. Cold and osmotic stress are similar, because in both the availability of water is reduced. Glycine betaine (GB) is one of the most common osmoprotectants in bacteria and possesses cryoprotectant properties. Our aim was to determine whether GB modifies the proportion of dormant Deinococcus sp. UDEC-P1 and Psychrobacter sp. UDEC-A5 cells exposed to osmotic stress. Both bacterial strains were incubated in the presence of up to 1 M NaCl with or without GB. Active and dormant cells were evaluated by both spectrophotometric and flow cytometry analysis. Without GB, Deinococcus sp. UDEC-P1 grew in the presence of 0.05 M NaCl, but with 5 mM GB grew at 0.1 M NaCl. Psychrobacter sp. UDEC-A5 grew in the presence of up to 0.25 M NaCl, but with 5 mM GB grew at 0.5 M NaCl. Under osmotic stress, the proportion of dormant cells of Deinococcus sp. UDEC-P1 and Psychrobacter sp. UDEC-A5 increased significantly (about eightfold and fivefold, respectively). The addition of GB (5 mM) exerted a different effect on the two strains, since it avoided the entrance into the dormancy of Psychrobacter sp. UDEC-A5 cells, but not of Deinococcus sp. UDEC-P1 cells. Our results suggest that the effect of GB on bacterial metabolism is strain dependent. For bacteria in which GB avoids dormancy, such as Psychrobacter sp. UDEC-A5, it could be a "double-edged sword" by reducing the "seed bank" available to recover the active population when favorable conditions return.
在压力下，细菌会增加休眠细胞的比例以确保其存活。冷胁迫和渗透胁迫相似，因为在这两种情况下，水的可用性都降低了。甘氨酸甜菜碱（GB）是细菌中最常见的渗透保护剂之一，具有抗冻保护特性。我们的目的是确定 GB 是否会改变暴露于渗透胁迫下的 Deinococcus sp. UDEC-P1 和 Psychrobacter sp. UDEC-A5 休眠细胞的比例。在存在高达 1 M NaCl 的情况下，两种细菌菌株均在存在或不存在 GB 的情况下孵育。通过分光光度法和流式细胞术分析评估活性细胞和休眠细胞。没有 GB 时，Deinococcus sp. UDEC-P1 在 0.05 M NaCl 中生长，但在 5 mM GB 存在下可在 0.1 M NaCl 中生长。Psychrobacter sp. UDEC-A5 可在高达 0.25 M NaCl 的存在下生长，但在 5 mM GB 存在下可在 0.5 M NaCl 中生长。在渗透胁迫下，Deinococcus sp. UDEC-P1 和 Psychrobacter sp. UDEC-A5 的休眠细胞比例显著增加（分别约为八倍和五倍）。GB（5 mM）的添加对两种菌株的影响不同，因为它阻止了 Psychrobacter sp. UDEC-A5 细胞进入休眠状态，但不能阻止 Deinococcus sp. UDEC-P1 细胞进入休眠状态。我们的结果表明，GB 对细菌代谢的影响取决于菌株。对于像 Psychrobacter sp. UDEC-A5 这样的细菌，GB 可以避免休眠，这可能是一把“双刃剑”，因为它减少了可用的“种子库”，从而降低了在有利条件下恢复活跃种群的能力。
