A novel exopolysaccharide pathway from a freshwater Sphingomonas isolate.
A novel exopolysaccharide pathway from a freshwater Sphingomonas isolate.
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来自淡水鞘氨醇单胞菌分离物的新型胞外多糖途径。
DOI：
10.1101/2023.11.03.565537
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发表时间：
2023
期刊：
影响因子：
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通讯作者：
Hershey,DavidM
中科院分区：
文献类型：
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作者：
Goetsch,AlexandraG;Ufearo,Daniel;Keiser,Griffin;Heiss,Christian;Azadi,Parastoo;Hershey,DavidM
细菌用各种特殊的多糖修饰它们的细胞包膜。这些聚糖的生物合成途径很复杂，最终产物在化学结构、物理性质和生物活性方面差异很大。这种巨大的多样性来自于将复杂的单糖结构单元集合排列成具有许多可能的连接构型的聚合物的能力。由于细菌聚糖的复杂化学性质，很少有生物合成途径被详细定义。为了更好地了解多糖生产在自然界中的广度，我们从密歇根湖分离出一种称为鞘氨醇单胞菌属LM 7的细菌，其精通胞外多糖（EPS）生产。我们通过筛选转座子突变体文库，确定了有助于LM 7中EPS生物合成的基因，以获得显示改变的菌落形态的菌落。一个基因簇被确定，似乎编码一个完整的wzy/wzx依赖的多糖组装途径。删除该簇中的单个基因导致非粘液样表型和相应的EPS分泌损失，证实LM 7组装了一种新的wzy/wzx依赖性多糖。我们从LM 7培养物中提取EPS，结果表明它含有3-和4-连接的葡萄糖，半乳糖和葡萄糖醛酸残基的线性链。最后，我们发现，我们确定的EPS途径偏离那些粘性多糖，如holdfast是保守的更高的α-变形菌。我们的方法，表征完整的生物合成途径的工程具有宝贵的特性的多糖的承诺。
Bacteria embellish their cell envelopes with a variety of specialized polysaccharides. Biosynthesis pathways for these glycans are complex, and final products vary greatly in their chemical structures, physical properties and biological activities. This tremendous diversity comes from the ability to arrange complex pools of monosaccharide building blocks into polymers with many possible linkage configurations. Due to the complex chemistry of bacterial glycans, very few biosynthetic pathways have been defined in detail. To better understand the breadth of polysaccharide production in nature we isolated a bacterium from Lake Michigan called Sphingomonas sp. LM7 that is proficient in exopolysaccharide (EPS) production. We identified genes that contribute to EPS biosynthesis in LM7 by screening a transposon mutant library for colonies displaying altered colony morphology. A gene cluster was identified that appears to encode a complete wzy/wzx-dependent polysaccharide assembly pathway. Deleting individual genes in this cluster caused a non-mucoid phenotype and a corresponding loss of EPS secretion, confirming that LM7 assembles a novel wzy/wzx-dependent polysaccharide. We extracted EPS from LM7 cultures and showed that it contains a linear chain of 3- and 4- linked glucose, galactose, and glucuronic acid residues. Finally, we found that the EPS pathway we identified diverges from those of adhesive polysaccharides such as the holdfast that are conserved in higher Alphaproteobacteria. Our approach of characterizing complete biosynthetic pathways holds promise for engineering of polysaccharides with valuable properties.