Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, Curitiba, Paraná, Brazil.
FEMS Microbiol Lett. 2011 Aug;321(1):50-7. doi: 10.1111/j.1574-6968.2011.02309.x. Epub 2011 May 31.
The main α-glucan synthesized by lichens of the genera Ramalina in the symbiotic state is isolichenan. This polysaccharide was not found in the aposymbiotically cultivated symbionts. It is still unknown if this glucan is produced by the mycobiont only in the presence of a photobiont, in a lichen thallus, or if the isolichenan suppression is influenced by the composition of culture medium used in its aposymbiotic cultive. Consequently, the latter hypothesis is tested in this study. Cultures of the mycobiont Ramalina complanata were obtained from germinated ascospores and cultivated on 4% glucose Lilly and Barnett medium. Freeze-dried colonies were defatted and their carbohydrates extracted successively with hot water and aqueous 10% KOH, each at 100 °C. The polysaccharides nigeran, laminaran and galactomannan were liberated, along with a lentinan-type β-glucan and a heteropolysaccharide (Man : Gal : Glc, 21 : 28 : 51). Nevertheless, the α-glucan isolichenan was not found in the extracts. It follows that it was probably a symbiotic product, synthesized by the mycobiont only in this particular microenvironment, in the presence of the photobiont in the lichen thallus. A discussion about polysaccharides found in the symbiotic thallus as well as in other aposymbiotic cultivated Ramalina mycobionts is also included.
地衣的共生状态下产生的主要α-葡聚糖是异层地衣聚糖。这种多糖在无共生状态下培养的共生体中未被发现。目前还不清楚这种葡聚糖是否仅在有光共生体存在的情况下由菌共生体产生，还是在lichen 地衣体中，或者异层地衣聚糖的抑制是否受到用于无共生培养的培养基组成的影响。因此，本研究检验了后一种假设。从萌发的子囊孢子中获得菌共生体 Ramalina complanata 的培养物，并在 4%葡萄糖 Lilly 和 Barnett 培养基上培养。冻干的菌落脱脂，然后分别用热水和 10%KOH 水溶液（均在 100°C）提取碳水化合物。释放出黑兰聚糖、昆布多糖和半乳甘露聚糖，以及一种香菇型β-葡聚糖和一种杂多糖（Man:Gal:Glc，21:28:51）。然而，提取物中未发现α-葡聚糖异层地衣聚糖。因此，它可能是一种共生产物，仅由菌共生体在这种特定的微环境中，在lichen 地衣体中的光共生体存在下合成。还包括了对共生地衣体以及其他无共生培养的 Ramalina 菌共生体中发现的多糖的讨论。
