Abstract：
Methylobacterium extorquens is a facultative methylotrophic Gram-negative bacterium, often associated with plants, that exhibits a unique ability to grow in the presence of high methanol concentrations, which serves as a single carbon energy source. We found that M. extorquens strain PA1 secretes a mixture of different exopolysaccharides (EPSs) when grown in reference medium or in presence of methanol, that induces the secretion of a peculiar and heterogenous mixture of EPSs, with different structure, composition, repeating units, bulk and a variable degree of methylation. These factors influenced 3D structure and supramolecular assets, diffusion properties and hydrodynamic radius, and likely contribute to increase methanol tolerance and cell stability. No direct methanol involvement in the EPSs solvation shell was detected, indicating that the polymer exposure to methanol is water mediated. The presence of methanol induces no changes in size and shape of the polymer chains, highlighting how water-methanol mixtures are a good solvent for refEPS and metEPS.
摘要：
甲基杆菌是兼性甲基营养革兰氏阴性细菌，通常与植物有关，在高甲醇浓度下表现出独特的生长能力，作为单一的碳能源。我们发现，当在参考培养基中或在甲醇存在下生长时，M.extorquens菌株PA1分泌不同胞外多糖（EPS）的混合物，诱导分泌特殊和异质的EPS混合物，具有不同的结构，composition,重复单位,批量和可变程度的甲基化。这些因素影响了3D结构和超分子资产，扩散特性和流体动力学半径，并可能有助于增加甲醇耐受性和细胞稳定性。未检测到甲醇直接参与EPS溶剂化外壳，这表明聚合物暴露于甲醇是水介导的。甲醇的存在不会引起聚合物链的大小和形状的变化，强调水-甲醇混合物是refEPS和metEPS的良好溶剂。
