Pharmaceutical Biotechnology, Ernst-Moritz-Arndt-University, Greifswald, Germany.
Institute for Microbiology, Ernst-Moritz-Arndt-University, Greifswald, Germany.
ISME J. 2014 Jul;8(7):1492-502. doi: 10.1038/ismej.2014.4. Epub 2014 Feb 13.
Members of the phylum Bacteroidetes are abundant in many marine ecosystems and are known to have a pivotal role in the mineralization of complex organic substrates such as polysaccharides and proteins. We studied the decomposition of the algal glycans laminarin and alginate by 'Gramella forsetii' KT0803, a bacteroidetal isolate from North Sea surface waters. A combined application of isotope labeling, subcellular protein fractionation and quantitative proteomics revealed two large polysaccharide utilization loci (PULs) that were specifically induced, one by alginate and the other by laminarin. These regulons comprised genes of surface-exposed proteins such as oligomer transporters, substrate-binding proteins, carbohydrate-active enzymes and hypothetical proteins. Besides, several glycan-specific TonB-dependent receptors and SusD-like substrate-binding proteins were expressed also in the absence of polysaccharide substrates, suggesting an anticipatory sensing function. Genes for the utilization of the beta-1,3-glucan laminarin were found to be co-regulated with genes for glucose and alpha-1,4-glucan utilization, which was not the case for the non-glucan alginate. Strong syntenies of the PULs of 'G. forsetii' with similar loci in other Bacteroidetes indicate that the specific response mechanisms of 'G. forsetii' to changes in polysaccharide availability likely apply to other Bacteroidetes. Our results can thus contribute to an improved understanding of the ecological niches of marine Bacteroidetes and their roles in the polysaccharide decomposition part of carbon cycling in marine ecosystems.
门杆菌的成员在许多海洋生态系统中大量存在，已知在多糖和蛋白质等复杂有机基质的矿化中起着关键作用。我们研究了来自北海表面水的杆菌属分离株“Gramella forsetii”KT0803 对藻类糖醛酸海藻酸盐和褐藻糖胶的分解作用。同位素标记、亚细胞蛋白分级分离和定量蛋白质组学的综合应用揭示了两个被特异性诱导的大型多糖利用基因座（PUL），一个由海藻酸盐诱导，另一个由褐藻糖胶诱导。这些调控子包含表面暴露蛋白的基因，如寡聚物转运蛋白、底物结合蛋白、碳水化合物活性酶和假设蛋白。此外，一些糖特异性 TonB 依赖性受体和 SusD 样底物结合蛋白也在没有多糖底物的情况下表达，这表明它们具有预期的传感功能。利用β-1,3-葡聚糖褐藻糖胶的基因与葡萄糖和α-1,4-葡聚糖利用的基因共同调控，但非葡聚糖海藻酸盐则不然。“G. forsetii”的 PUL 与其他杆菌中的类似基因座具有很强的同线性，这表明“G. forsetii”对多糖可用性变化的特定响应机制可能适用于其他杆菌。因此，我们的研究结果有助于更好地理解海洋杆菌的生态位及其在海洋生态系统多糖分解部分的碳循环中的作用。
