Breedveld M W, Hadley J A, Miller K J
Department of Food Science, Pennsylvania State University, University Park 16802, USA.
J Bacteriol. 1995 Nov;177(22):6346-51. doi: 10.1128/jb.177.22.6346-6351.1995.
The periplasmic cyclic beta-1,2-glucans produced by bacteria within the Rhizobiaceae family provide functions during hypo-osmotic adaptation and plant infection. In Rhizobium meliloti, these molecules are highly modified with phosphoglycerol and succinyl substituents, and it is possible that the anionic character of these glucans is important for their functions. In the present study, we have used a thin-layer chromatographic screening method to identify a novel R. meliloti mutant specifically blocked in its ability to transfer phosphoglycerol substituents to the cyclic beta-1,2-glucan backbone. Further analysis revealed that the cyclic glucans produced by this mutant contained elevated levels of succinyl substituents. As a result, the overall anionic charge on the cyclic beta-1,2-glucans was found to be similar to that of wild-type cells. Despite this difference in cyclic beta-1,2-glucan structure, the mutant was shown to effectively nodulate alfalfa and to grow as well as wild-type cells in hypo-osmotic media.
根瘤菌科细菌产生的周质环状β-1,2-葡聚糖在低渗适应和植物感染过程中发挥作用。在苜蓿根瘤菌中，这些分子被磷酸甘油和琥珀酰取代基高度修饰，这些葡聚糖的阴离子特性可能对其功能很重要。在本研究中，我们使用了一种薄层色谱筛选方法来鉴定一种新型苜蓿根瘤菌突变体，该突变体在将磷酸甘油取代基转移到环状β-1,2-葡聚糖主链的能力上存在特异性缺陷。进一步分析表明，该突变体产生的环状葡聚糖含有更高水平的琥珀酰取代基。结果发现，环状β-1,2-葡聚糖上的总阴离子电荷与野生型细胞相似。尽管环状β-1,2-葡聚糖结构存在这种差异，但该突变体仍能有效地使苜蓿结瘤，并且在低渗培养基中与野生型细胞一样生长良好。
