Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02167, and Department of Microbiology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California 90024.
Appl Environ Microbiol. 1992 Aug;58(8):2438-43. doi: 10.1128/aem.58.8.2438-2443.1992.
Methanohalophilus strain FDF1, a member of the halophilic genus of methanogens, can grow over a range of external NaCl concentrations from 1.2 to 2.9 M and utilize methanol, trimethylamine, and dimethyl sulfide as substrates for methanogenesis. It produces the osmolytes glycine betaine, beta-glutamine, and N-acetyl-beta-lysine with increasing external NaCl, but the relative ratio of these zwitterions depends primarily on the methanogenic substrate and less on the external osmolarity. When the cells are grown on methanol in defined medium, accumulation of glycine betaine predominates over the other zwitterionic solutes. The cells also synthesized a carbohydrate which was not detected in cells grown on trimethylamine. This negatively charged compound, identified as alpha-glucosylglycerate from the C and H chemical shifts, does not act as an osmoregulatory solute in the salt range 1.4 to 2.7 M in this methanogen as evidenced by its invariant intracellular concentration. CH(3)OH-pulse/CH(3)OH-chase experiments were used to determine half-lifes for these organic solute pools in the cells. l-alpha-Glutamate showed a rapid loss of heavy isotope, indicating that l-alpha-glutamate functions as a biosynthetic intermediate in these cells. Measurable turnover rates for both beta-glutamine, which acts as an osmolyte, and alpha-glucosylglycerate suggest that they function as metabolic intermediates as well. Molecules which function solely as osmolytes (glycine betaine and N-acetyl-beta-lysine) showed a slower turnover consistent with their roles as osmotic solutes in Methanohalophilus strain FDF1.
嗜盐甲烷菌 FDF1 菌株是一种能在 1.2 到 2.9 M 盐浓度范围内生长的嗜盐产甲烷菌，能以甲醇、三甲胺和二甲基硫作为产甲烷的基质。它会随着外部 NaCl 的增加产生甘氨酸甜菜碱、β-谷氨酰胺和 N-乙酰-β-赖氨酸等渗透物，但这些两性离子的相对比例主要取决于产甲烷的基质，而与外部渗透压关系较小。当细胞在有确定成分的培养基中以甲醇为基质生长时，甘氨酸甜菜碱的积累会超过其他两性离子溶质。细胞还合成了一种在以三甲胺为基质的细胞中没有检测到的碳水化合物。这种带负电荷的化合物，根据 C 和 H 的化学位移被鉴定为α-葡萄糖基甘油酸，在盐浓度为 1.4 到 2.7 M 的范围内，它不像渗透压调节剂一样在这种产甲烷菌中起作用，这一点从其不变的细胞内浓度可以证明。CH(3)OH-脉冲/CH(3)OH-追踪实验被用来确定这些有机溶质库在细胞中的半衰期。l-α-谷氨酸显示出重同位素的快速损失，表明 l-α-谷氨酸在这些细胞中作为生物合成中间体发挥作用。β-谷氨酰胺和α-葡萄糖基甘油酸作为渗透物的可测量周转率表明它们也作为代谢中间体发挥作用。仅作为渗透物（甘氨酸甜菜碱和 N-乙酰-β-赖氨酸）的分子显示出较慢的周转率，这与它们在嗜盐甲烷菌 FDF1 中作为渗透溶质的作用一致。
