Abstract The heterocyte (heterocyst) glycolipid (HG) content of heterocytous (heterocystous) cyanobacteria can principally be separated into two different types. In the first type, the aglycone moiety attached to the sugar headgroup exclusively contains hydroxyl functionalities resulting in the formation of HG diols and HG triols. In the second type, one of the hydroxyl groups is replaced by a ketone functionality giving rise to HG keto-ols and HG keto-diols. In the N2-fixing heterocytous cyanobacterium Microchaete sp. PCC 7126 both types of HGs were dominant and consisted primarily of two structural isomers each of the HG28 diol and HG28 keto-ol. In addition to these well-characterized HGs, Microchaete sp. PCC 7126 also contained a yet undescribed type of HG that based on comparison of retention times, molecular weight and mass spectrometry consisted of a hexose headgroup attached to an aglycone moiety with 28 carbon atoms at which two instead of one ketone functionalities were attached. Hence, the novel HG structure was identified as HG28 diketone. This study thus provides further evidence for the large structural diversity of HGs, which allows chemotaxonomic profiling of heterocytous cyanobacteria and in turn studying the community composition of these important diazotrophs in the geological rock record.

中文翻译：

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杂细胞糖脂二酮：一种新型的 N2 固定异细胞蓝藻微毛虫的生物标志物

摘要 异细胞（heterocystous）蓝藻的异细胞（heterocyst）糖脂（HG）含量主要可分为两种不同的类型。在第一种类型中，与糖头基相连的糖苷配基部分仅包含羟基官能团，导致形成 HG 二醇和 HG 三醇。在第二种类型中，羟基之一被酮官能团取代，产生 HG 酮醇和 HG 酮二醇。在固定 N2 的异细胞蓝藻 Microchaete sp. 中。PCC 7126 两种类型的 HG 均占主导地位，主要由 HG28 二醇和 HG28 酮醇的两种结构异构体组成。除了这些特征明确的 HG 外，微毛纲物种。PCC 7126 还包含一种尚未描述的基于保留时间比较的 HG，分子量和质谱由连接到具有 28 个碳原子的糖苷配基部分的己糖头基组成，在该部分连接了两个而不是一个酮官能团。因此，新的 HG 结构被鉴定为 HG28 二酮。因此，这项研究为 HG 的大量结构多样性提供了进一步的证据，这允许对异细胞蓝藻进行化学分类学分析，进而研究地质岩石记录中这些重要固氮菌的群落组成。