Center for Neuroscience and Cell Biology, University of Coimbra, 3004-517 Coimbra, Portugal.
Environ Microbiol. 2011 Aug;13(8):2056-77. doi: 10.1111/j.1462-2920.2010.02390.x. Epub 2010 Dec 22.
A decade ago the compatible solutes mannosylglycerate (MG) and glucosylglycerate (GG) were considered to be rare in nature. Apart from two species of thermophilic bacteria, Thermus thermophilus and Rhodothermus marinus, and a restricted group of hyperthermophilic archaea, the Thermococcales, MG had only been identified in a few red algae. Glucosylglycerate was considered to be even rarer and had only been detected as an insignificant solute in two halophilic microorganisms, a cyanobacterium, as a component of a polysaccharide and of a glycolipid in two actinobacteria. Unlike the hyper/thermophilic MG-accumulating microorganisms, branching close to the root of the Tree of Life, those harbouring GG shared a mesophilic lifestyle. Exceptionally, the thermophilic bacterium Persephonella marina was reported to accumulate GG. However, and especially owing to the identification of the key-genes for MG and GG synthesis and to the escalating numbers of genomes available, a plethora of new organisms with the resources to synthesize these solutes has been recognized. The accumulation of GG as an 'emergency' compatible solute under combined salt stress and nitrogen-deficient conditions now seems to be a disseminated survival strategy from enterobacteria to marine cyanobacteria. In contrast, the thermophilic and extremely radiation-resistant bacterium Rubrobacter xylanophilus is the only actinobacterium known to accumulate MG, and under all growth conditions tested. This review addresses the environmental factors underlying the accumulation of MG, GG and derivatives in bacteria and archaea and their roles during stress adaptation or as precursors for more elaborated macromolecules. The diversity of pathways for MG and GG synthesis as well as those for some of their derivatives is also discussed. The importance of glycerate-derived organic solutes in the microbial world is only now being recognized. Their stress-dependent accumulation and the molecular aspects of their interactions with biomolecules have already fuelled several emerging applications in biotechnology and biomedicine.
十年前，相容溶质甘露糖甘油酯（MG）和葡萄糖甘油酯（GG）被认为在自然界中很少见。除了两种嗜热细菌，Thermus thermophilus 和 Rhodothermus marinus，以及少数超嗜热古菌 Thermococcales 之外，MG 只在少数红藻中被鉴定出来。葡萄糖甘油酯被认为更为罕见，仅在两种嗜盐微生物中作为一种不重要的溶质被检测到，一种蓝细菌作为多糖的成分，两种放线菌作为糖脂的成分。与积累高/嗜热 MG 的微生物不同，它们与生命之树的根部接近，那些积累 GG 的微生物具有中温生活方式。例外的是，嗜热细菌 Persephonella marina 被报道积累 GG。然而，特别是由于 MG 和 GG 合成的关键基因的鉴定以及可用基因组数量的增加，已经认识到具有合成这些溶质资源的大量新生物体。现在看来，在盐胁迫和氮缺乏条件下积累 GG 作为一种“紧急”相容溶质是从肠杆菌到海洋蓝细菌传播的生存策略。相比之下，嗜热和极耐辐射的细菌 Rubrobacter xylanophilus 是唯一已知积累 MG 的放线菌，并且在所有测试的生长条件下都是如此。本综述探讨了细菌和古菌中 MG、GG 和衍生物积累的环境因素及其在应激适应或作为更复杂大分子前体中的作用。还讨论了 MG 和 GG 合成以及它们一些衍生物的途径的多样性。甘油酸盐衍生的有机溶质在微生物世界中的重要性才刚刚被认识到。它们在应激条件下的积累以及它们与生物分子相互作用的分子方面已经为生物技术和生物医学中的几个新兴应用提供了动力。
