Appl Environ Microbiol. 1997 Jan;63(1):220-6. doi: 10.1128/aem.63.1.220-226.1997.
The identity and concentrations of intracellular organic solutes were determined by nuclear magnetic resonance spectroscopy for two strains of aerobic, gram-negative bacteria isolated from Mono Lake, Calif., an alkaline, moderately hypersaline lake. Ectoine (1,4,5,6-tetrahydro-2-methyl-4-pyrimidinecarboxylic acid) was the major endogenous solute in both organisms. Concentrations of ectoine varied with external NaCl levels in strain ML-D but not in strain ML-G, where the level was high but invariant from 1.5 to 3.0 M NaCl. Hydroxyectoine also occurred in strain ML-D, especially at elevated NaCl concentrations (2.5 and 3.0 M), but at levels lower than those of ectoine. Exogenous organic solutes that might occur in Mono Lake were examined for their effects on the de novo synthesis of ectoine. Dimethylsulfoniopropionate (DMSP) (0.1 or 1 mM) did not significantly lower ectoine levels in either isolate, and only strain ML-G showed any capacity for DMSP accumulation. With nitrogen limitation, however, DMSP (0.1 mM) substituted for ectoine in strain ML-G and became the main organic solute. Glycine betaine (GB) was more effective than DMSP in affecting ectoine levels, principally in strain ML-D. Strain ML-D accumulated GB to 50 or 67% of its organic solute pool at 2.5 M NaCl, at an external level of 0.1 or 1 mM GB, respectively. Strain ML-D also accumulated arsenobetaine. The methylated zwitterionic compounds, probably metabolic products of phytoplankton (DMSP and GB) or brine shrimps (arsenobetaine) in Mono Lake, may function as osmolytes for indigenous bacteria when present at high concentrations or under conditions of nitrogen limitation or salt stress.
两种从加利福尼亚州莫诺湖（一个碱性、中度过盐湖泊）中分离出来的需氧革兰氏阴性细菌，通过核磁共振波谱法确定了其细胞内有机溶质的身份和浓度。两种生物的主要内源性溶质都是章鱼胺（1,4,5,6-四氢-2-甲基-4-嘧啶羧酸）。在 ML-D 菌株中，章鱼胺的浓度随外部 NaCl 水平而变化，但在 ML-G 菌株中，其浓度虽然很高，但在 1.5 至 3.0 M NaCl 范围内保持不变。羟基章鱼胺也存在于 ML-D 菌株中，尤其是在高 NaCl 浓度（2.5 和 3.0 M）下，但浓度低于章鱼胺。还检查了可能在莫诺湖中存在的外源性有机溶质对章鱼胺从头合成的影响。二甲基砜丙酸盐（DMSP）（0.1 或 1 mM）均未显著降低两种分离株中的章鱼胺水平，只有 ML-G 菌株显示出任何积累 DMSP 的能力。然而，在氮限制下，DMSP（0.1 mM）在 ML-G 菌株中替代了章鱼胺，成为主要的有机溶质。甘氨酸甜菜碱（GB）比 DMSP 更有效地影响章鱼胺水平，主要在 ML-D 菌株中。ML-D 菌株在 2.5 M NaCl 下，分别在 0.1 或 1 mM 的外源性 GB 水平下，将 GB 积累到有机溶质库的 50 或 67%。ML-D 菌株还积累砷甜菜碱。这些甲基化两性离子化合物，可能是莫诺湖中浮游植物（DMSP 和 GB）或卤虫（砷甜菜碱）的代谢产物，当它们在高浓度存在或在氮限制或盐胁迫条件下时，可能作为土著细菌的渗透调节剂发挥作用。
