Structural characterization and ecological roles of a novel exopolysaccharide from the deep-sea psychrotolerant bacterium Pseudoalteromonas sp SM9913
Structural characterization and ecological roles of a novel exopolysaccharide from the deep-sea psychrotolerant bacterium Pseudoalteromonas sp SM9913
复制标题
深海耐冷细菌假交替单胞菌 SM9913 的新型胞外多糖的结构特征和生态作用
DOI：
10.1099/mic.0.2006/003327-0
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发表时间：
2007-05-01
期刊：
影响因子：
2.8
通讯作者：
Zhang, Yuzhong
中科院分区：
文献类型：
--
作者：
Qin, Guokui;Zhu, Lizhi;Zhang, Yuzhong
假交替单胞菌属(Pseudoternomonas sp.)SM9913是从深海沉积物中分离到的一株耐冷菌。本工作对该菌株分泌的胞外多糖(EPS)的结构特征及其生态作用进行了研究。在30~10℃范围内，随着培养温度的降低，胞外多糖产量增加，在最适培养条件下(15℃，52h)，胞外多糖产量可达5.25g L(-1)(干重)。对EPS组分进行了纯化，并结合核磁共振光谱、高分辨质谱分析和甲基化分析鉴定了其结构。糖基、乙酰基和乙氧基的比例接近4：5：1。EPS的主要糖基是6-连接葡萄糖(61.8%)，其他糖基单元包括末端阿拉伯呋喃葡萄糖(11.0%)和吡喃葡萄糖(11.2%)残基以及少量其他糖衍生物。其结构与已报道的其他海洋细菌的EPSS不同。除阐明EPS的结构外，还研究了EPS的生态作用。该EPS可以通过抑制MCP-01的自溶来提高该菌株分泌的耐冷蛋白酶MCP-01的稳定性。它能与多种金属离子结合，包括Fe2+、Zn2+、Cu2+、Co2+。它也是一种很好的絮凝剂，可以凝聚胶体和悬浮颗粒。这些结果表明，SM9913菌株分泌的EPS可能有助于该菌株丰富深海环境中的蛋白质颗粒和痕量金属，稳定分泌的冷适应蛋白酶，避免其扩散。这被认为是首次关于深海耐冷细菌分泌的EPS的结构及其生态作用的报道。根据这些结果和其他研究，提出了深海耐冷菌株SM9913的生活方式示意图。
Pseudoalteromonas sp. SM9913 is a psychrotolerant bacterium isolated from deep-sea sediment. The structural characterization and ecological roles of the exopolysaccharide (EPS) secreted by this strain were studied in this work. The yield of the EPS increased as the culture temperature decreased in the range 30-10 degrees C, and it reached 5.25 g l(-1) (dry weight) under optimal growth conditions (15 degrees C, 52 h). EPS fraction was purified and its structure was identified by the combination of NMR spectra, high-resolution mass spectrometry (HRMS) analysis and methylation analysis. The ratio of the sugar units, the acetyl group and the ethoxyl group was close to 4: 5: 1. The major sugar unit of the EPS was 6-linked glucose (61.8 %); other sugar units present included terminal arabinofuranosyl (11.0 %) and glucopyranosyl (11.2 %) residues and a small amount of other sugar derivatives. Its structure was different from EPSs reported for other marine bacteria. Besides the structural elucidation of the EPS, its ecological roles were studied. This EPS could enhance the stability of the cold-adapted protease MCP-01 secreted by the same strain through preventing its autolysis. It could bind many metal ions, including Fe2+, Zn2+, Cu2+, Co2+. It was also a very good flocculating agent and could conglomerate colloidal and suspended particles. These results indicated that the EPS secreted by strain SM9913 might help this strain enrich the proteinaceous particles and the trace metals in the deep-sea environment, stabilize the secreted cold-adapted proteases and avoid its diffusion. This is believed to be the first report on the structure of the EPS secreted by a deep-sea psychrotolerant bacterium and its ecological roles. According to these results and other studies, a schematic diagram of the lifestyle of the deep-sea psychrotolerant strain SM9913 is suggested.