Colony Organization in the Green Alga Botryococcus braunii (Race B) Is Specified by a Complex Extracellular Matrix
Colony Organization in the Green Alga Botryococcus braunii (Race B) Is Specified by a Complex Extracellular Matrix
复制标题
DOI：
10.1128/ec.00184-12
复制
发表时间：
2012-12-01
期刊：
影响因子：
--
通讯作者：
Goodenough, Ursula
中科院分区：
文献类型：
--
作者：
Weiss, Taylor L.;Roth, Robyn;Goodenough, Ursula
布氏芽孢杆菌是一种群体绿藻，其细胞通过复杂的细胞外基质(ECM)结合，并产生大量的液态碳氢化合物，这些液体碳氢化合物很容易转化为传统的内燃机燃料。我们使用快速冷冻深蚀刻电子显微镜和生化/组织化学分析来阐明布氏芽孢杆菌细胞/集落组织和组成的许多新特征。细胞内的脂体与叶绿体和内质网(ER)联系在一起，但没有证据表明是分泌的。内质网显示出明显的窗口，形成一个与细胞膜直接接触的连续的皮质下系统。ECM有三个截然不同的组成部分。(I)每个细胞被含有β-1，4-和/或β-1，3-葡聚糖的纤维状细胞壁包围。(2)管腔内的ECM空间充满了渗入液态碳氢化合物的交联烃网络。(Iii)菌落被封闭在挡土墙中，挡土墙上覆盖着以阿拉伯糖-半乳糖多糖为主的纤维鞘，阿拉伯糖-半乳糖多糖隔离ECM液体碳氢化合物。每个细胞顶端与挡土墙相连，并参与其合成。挡土墙结构域也在细胞之间形成“窗帘”，一些结构域自己折叠起来，穿透母殖民地的碳氢化合物内部，将其划分为子殖民地。我们认为挡墙成分是在顶端高尔基体中合成的，被输送到顶端的内质网开窗，并组装在顶端细胞壁的表面，在顶端细胞壁上，一层蛋白质颗粒层显然参与了纤维的形态发生。我们进一步认为，碳氢化合物是由非尖端内质网产生的，直接输送到连续的细胞膜，并穿过非顶端细胞壁进入基于碳氢化合物的ECM。
Botryococcus braunii is a colonial green alga whose cells associate via a complex extracellular matrix (ECM) and produce prodigious amounts of liquid hydrocarbons that can be readily converted into conventional combustion engine fuels. We used quick-freeze deep-etch electron microscopy and biochemical/histochemical analysis to elucidate many new features of B. braunii cell/colony organization and composition. Intracellular lipid bodies associate with the chloroplast and endoplasmic reticulum (ER) but show no evidence of being secreted. The ER displays striking fenestrations and forms a continuous subcortical system in direct contact with the cell membrane. The ECM has three distinct components. (i) Each cell is surrounded by a fibrous beta-1, 4- and/or beta-1, 3-glucan-containing cell wall. (ii) The intracolonial ECM space is filled with a cross-linked hydrocarbon network permeated with liquid hydrocarbons. (iii) Colonies are enclosed in a retaining wall festooned with a fibrillar sheath dominated by arabinose-galactose polysaccharides, which sequesters ECM liquid hydrocarbons. Each cell apex associates with the retaining wall and contributes to its synthesis. Retaining-wall domains also form "drapes" between cells, with some folding in on themselves and penetrating the hydrocarbon interior of a mother colony, partitioning it into daughter colonies. We propose that retaining-wall components are synthesized in the apical Golgi apparatus, delivered to apical ER fenestrations, and assembled on the surfaces of apical cell walls, where a proteinaceous granular layer apparently participates in fibril morphogenesis. We further propose that hydrocarbons are produced by the nonapical ER, directly delivered to the contiguous cell membrane, and pass across the nonapical cell wall into the hydrocarbon-based ECM.