Furusawa Go, Azami Nor Azura, Teh Aik-Hong
Centre for Chemical Biology, Universiti Sains Malaysia, Bayan Lepas, Penang, Malaysia.
PeerJ. 2021 Mar 9;9:e10929. doi: 10.7717/peerj.10929. eCollection 2021.
Oligosaccharides from polysaccharides containing uronic acids are known to have many useful bioactivities. Thus, polysaccharide lyases (PLs) and glycoside hydrolases (GHs) involved in producing the oligosaccharides have attracted interest in both medical and industrial settings. The numerous polysaccharide lyases and glycoside hydrolases involved in producing the oligosaccharides were isolated from soil and marine microorganisms. Our previous report demonstrated that an agar-degrading bacterium, sp. CCB-QB4, isolated from a coastal area of Penang, Malaysia, possessed 183 glycoside hydrolases and 43 polysaccharide lyases in the genome. We expected that the strain might degrade and use uronic acid-containing polysaccharides as a carbon source, indicating that the strain has a potential for a source of novel genes for degrading the polysaccharides.
To confirm the expectation, the QB4 cells were cultured in artificial seawater media with uronic acid-containing polysaccharides, namely alginate, pectin (and saturated galacturonate), ulvan, and gellan gum, and the growth was observed. The genes involved in degradation and utilization of uronic acid-containing polysaccharides were explored in the QB4 genome using CAZy analysis and BlastP analysis.
The QB4 cells were capable of using these polysaccharides as a carbon source, and especially, the cells exhibited a robust growth in the presence of alginate. 28 PLs and 22 GHs related to the degradation of these polysaccharides were found in the QB4 genome based on the CAZy database. Eleven polysaccharide lyases and 16 glycoside hydrolases contained lipobox motif, indicating that these enzymes play an important role in degrading the polysaccharides. Fourteen of 28 polysaccharide lyases were classified into ulvan lyase, and the QB4 genome possessed the most abundant ulvan lyase genes in the CAZy database. Besides, genes involved in uronic acid metabolisms were also present in the genome. These results were consistent with the cell growth. In the pectin metabolic pathway, the strain had genes for three different pathways. However, the growth experiment using saturated galacturonate exhibited that the strain can only use the pathway related to unsaturated galacturonate.
已知含有糖醛酸的多糖中的寡糖具有许多有用的生物活性。因此，参与生产寡糖的多糖裂解酶（PLs）和糖苷水解酶（GHs）在医学和工业领域都引起了人们的兴趣。众多参与生产寡糖的多糖裂解酶和糖苷水解酶是从土壤和海洋微生物中分离出来的。我们之前的报告表明，从马来西亚槟城沿海地区分离出的一种琼脂降解细菌，即CCB-QB4菌株，在基因组中拥有183种糖苷水解酶和43种多糖裂解酶。我们预计该菌株可能会降解并利用含糖醛酸的多糖作为碳源，这表明该菌株有潜力成为降解多糖的新基因来源。
为了证实这一预期，将QB4细胞在含有含糖醛酸多糖（即海藻酸盐、果胶（和饱和半乳糖醛酸）、岩藻聚糖和结冷胶）的人工海水培养基中培养，并观察其生长情况。使用CAZy分析和BlastP分析在QB4基因组中探索参与含糖醛酸多糖降解和利用的基因。
QB4细胞能够利用这些多糖作为碳源，特别是在海藻酸盐存在的情况下，细胞表现出强劲的生长。基于CAZy数据库，在QB4基因组中发现了28种与这些多糖降解相关的多糖裂解酶和22种糖苷水解酶。11种多糖裂解酶和16种糖苷水解酶含有脂质框基序，表明这些酶在多糖降解中起重要作用。28种多糖裂解酶中有14种被归类为岩藻聚糖裂解酶，并且QB4基因组在CAZy数据库中拥有最丰富的岩藻聚糖裂解酶基因。此外，基因组中还存在参与糖醛酸代谢的基因。这些结果与细胞生长情况一致。在果胶代谢途径中，该菌株具有三种不同途径的基因。然而，使用饱和半乳糖醛酸的生长实验表明，该菌株只能使用与不饱和半乳糖醛酸相关的途径。
