Khmelenina VN, Kalyuzhnaya MG, Sakharovsky VG, Suzina NE, Trotsenko YA, Gottschalk G
Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, 142292 Pushchino, Moscow region, Russia.
Arch Microbiol. 1999 Nov;172(5):321-9. doi: 10.1007/s002030050786.
By using (1)H- and (13)C-NMR spectroscopy, an accumulation of sucrose and two cyclic amino acids [ectoine (1,4,5, 6-tetrahydro-2-methyl-4-pyrimidine carboxylic acid) and 5-oxoproline (pyrrolidone carboxylic acid)] was detected in the halotolerant methanotrophs Methylobacter alcaliphilus 20Z and Methylobacter modestohalophilus 10S. The organic solute pool was found to increase upon raising the NaCl concentration. In M. alcaliphilus 20Z, the intracellular level of the total solutes was shown to be sufficient to balance the osmotic pressure of the medium, whereas in M. modestohalophilus 10S their content was several times lower. Additionally, phosphatidylglycerol and phosphatidylcholine were predominant cell phospholipids in salt-adapted M. alcaliphilus 20Z. However, no phosphatidylcholine was found in M. modestohalophilus 10S, and the portion of phosphatidylglycerol increased while phosphatidylethanolamine decreased upon elevated external NaCl concentrations. Regularly arranged glycoprotein surface layers (S-layers) of hexagonal and linear (p2) symmetry were observed on the outer cell walls of M. alcaliphilus 20Z and M. modestohalophilus 10S. The S-layer in M alcaliphilus 20Z consisting of tightly packed, cup-shaped subunits was lost during growth at pH 7.2 (the lowest possible pH) in the absence of NaCl. Hence, osmoadaptation in the methanotrophs studied involves structure/function alterations of cell envelopes and changes in the chemical composition of membranes as well as de novo synthesis of compatible solutes.
通过使用氢-1（¹H）和碳-13（¹³C）核磁共振光谱法，在耐盐甲烷氧化菌嗜碱甲基杆菌20Z和适度嗜盐甲基杆菌10S中检测到蔗糖以及两种环状氨基酸（四氢嘧啶（1,4,5,6-四氢-2-甲基-4-嘧啶羧酸）和5-氧代脯氨酸（吡咯烷酮羧酸））的积累。发现随着氯化钠浓度的升高，有机溶质池会增加。在嗜碱甲基杆菌20Z中，总溶质的细胞内水平足以平衡培养基的渗透压，而在适度嗜盐甲基杆菌10S中，它们的含量要低几倍。此外，磷脂酰甘油和磷脂酰胆碱是适应盐环境的嗜碱甲基杆菌20Z中的主要细胞磷脂。然而，在适度嗜盐甲基杆菌10S中未发现磷脂酰胆碱，并且随着外部氯化钠浓度的升高，磷脂酰甘油的比例增加，而磷脂酰乙醇胺减少。在嗜碱甲基杆菌20Z和适度嗜盐甲基杆菌10S的外细胞壁上观察到具有六边形和线性（p2）对称性的规则排列的糖蛋白表面层（S层）。嗜碱甲基杆菌20Z中由紧密堆积的杯状亚基组成的S层在无氯化钠的pH 7.2（可能的最低pH）条件下生长时会丢失。因此，所研究的甲烷氧化菌中的渗透适应涉及细胞包膜的结构/功能改变、膜化学成分的变化以及相容性溶质的从头合成。
