Universität Rostock, Institut für Biowissenschaften, Abt. Pflanzenphysiologie, Einsteinstrasse 3, D-18059 Rostock, Germany.
Environ Microbiol. 2010 Jan;12(1):83-94. doi: 10.1111/j.1462-2920.2009.02045.x. Epub 2009 Sep 4.
The synthesis and accumulation of compatible solutes represent an essential part of the salt acclimation strategy of microorganisms. Glucosylglycerol is considered to be the typical compatible solute among marine cyanobacteria. However, genes that encode enzymes for the synthesis of glucosylglycerol were not detected in the genome sequences of marine picoplanktonic Prochlorococcus strains. Instead, we noticed the presence of genes that putatively encode for glucosylglycerate (GGA) synthesis among Prochlorococcus and most other closely related marine picocyanobacteria. Recombinant proteins from Prochlorococcus marinus SS120 and Synechococcus sp. PCC 7002 exhibited glucosyl-phosphoglycerate synthase (GpgS) activity, and GpgS is a key enzyme of GGA synthesis. GGA accumulation was found to be salt- as well as nitrogen-regulated in the coastal strain Synechococcus sp. PCC 7002. Moreover, GGA was also detected in all picoplanktonic Prochlorococcus and Synechococcus strains harbouring gpgS genes, especially under N-limiting conditions. These results suggest that marine picocyanobacteria acquired the capacity to synthesize the negatively charged compound GGA during their evolution. Our results establish GGA as the fifth most widespread compatible solute among cyanobacteria. Additionally, GGA appears to replace glutamate as an anion to counter monovalent cations in marine picocyanobacteria from N-poor environments.
相容溶质的合成和积累是微生物盐适应策略的重要组成部分。葡萄糖基甘油被认为是海洋蓝细菌中典型的相容溶质。然而，在海洋微微型浮游植物原绿球藻菌株的基因组序列中并未检测到编码葡萄糖基甘油合成酶的基因。相反，我们注意到在原绿球藻和大多数其他密切相关的海洋微微型蓝细菌中存在推测编码葡萄糖基甘油酸（GGA）合成的基因。来自海洋原绿球藻 SS120 和聚球藻 PCC 7002 的重组蛋白表现出葡萄糖基磷酸甘油酸合酶（GpgS）活性，而 GpgS 是 GGA 合成的关键酶。在沿海的聚球藻 PCC 7002 中发现 GGA 的积累既受盐度调控又受氮调控。此外，在携带 gpgS 基因的所有微微型原绿球藻和聚球藻菌株中都检测到了 GGA，尤其是在氮限制条件下。这些结果表明，海洋微微型蓝细菌在进化过程中获得了合成带负电荷化合物 GGA 的能力。我们的研究结果确立了 GGA 是蓝细菌中第五种广泛存在的相容溶质。此外，在氮缺乏环境中的海洋微微型蓝细菌中，GGA 似乎取代谷氨酸作为阴离子来抗衡单价阳离子。
