Verrucomicrobia use hundreds of enzymes to digest the algal polysaccharide fucoidan
Verrucomicrobia use hundreds of enzymes to digest the algal polysaccharide fucoidan
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DOI：
10.1038/s41564-020-0720-2
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发表时间：
2020-05-25
影响因子：
28.3
通讯作者：
Hehemann, Jan-Hendrik
中科院分区：
文献类型：
--
作者：
Sichert, Andreas;Corzett, Christopher H.;Hehemann, Jan-Hendrik
褐藻是全球碳循环中的重要参与者，每年将二氧化碳固定到1 Gt的生物质中，但岩藻聚糖-它们的主要细胞壁多糖-的命运仍然知之甚少。岩藻聚糖的微生物降解比其他多糖慢，表明岩藻聚糖更难降解，并可能在海洋中螯合碳。这可能是由于岩藻聚糖的复杂、分支和高度硫酸化的结构，这在褐藻物种之间也有所不同。在这里，我们表明，'慢单胞菌'属。CC 4，属于Verrucomicrobia，获得了一个非常复杂的机械降解六种不同的岩藻聚糖。该菌株积累了284个推定的岩藻聚糖酶，包括糖苷水解酶，硫酸酯酶和碳水化合物酯酶，主要位于0.89兆碱基对质粒上。蛋白质组学表明，这些酶组装成底物特异性途径，需要约100个酶，每个岩藻多糖从不同种类的褐藻。这些酶将岩藻依聚糖降解为岩藻糖，岩藻糖在蛋白质组昂贵的细菌微区室中代谢，该微区室在空间上限制有毒中间体乳醛的代谢。海洋宏基因组和微生物基因组表明，包括“慢单胞菌”在内的疣微菌属是岩藻聚糖和其他复杂多糖的丰富和高度专业化的降解菌。总的来说，这些途径的复杂性强调了为什么岩藻聚糖可能是不稳定的，降解速度更慢，因为只有高度专业化的生物才能在海洋中有效地降解它们。“慢单胞菌”--一种来自疣微菌门的海洋微生物--具有>200种不同的糖苷水解酶和硫酸酯酶，能够消化藻类多糖岩藻依聚糖，其被认为是我们海洋中的一种可降解的碳源。
Brown algae are important players in the global carbon cycle by fixing carbon dioxide into 1 Gt of biomass annually, yet the fate of fucoidan-their major cell wall polysaccharide-remains poorly understood. Microbial degradation of fucoidans is slower than that of other polysaccharides, suggesting that fucoidans are more recalcitrant and may sequester carbon in the ocean. This may be due to the complex, branched and highly sulfated structure of fucoidans, which also varies among species of brown algae. Here, we show that 'Lentimonas' sp. CC4, belonging to the Verrucomicrobia, acquired a remarkably complex machinery for the degradation of six different fucoidans. The strain accumulated 284 putative fucoidanases, including glycoside hydrolases, sulfatases and carbohydrate esterases, which are primarily located on a 0.89-megabase pair plasmid. Proteomics reveals that these enzymes assemble into substrate-specific pathways requiring about 100 enzymes per fucoidan from different species of brown algae. These enzymes depolymerize fucoidan into fucose, which is metabolized in a proteome-costly bacterial microcompartment that spatially constrains the metabolism of the toxic intermediate lactaldehyde. Marine metagenomes and microbial genomes show that Verrucomicrobia including 'Lentimonas' are abundant and highly specialized degraders of fucoidans and other complex polysaccharides. Overall, the complexity of the pathways underscores why fucoidans are probably recalcitrant and more slowly degraded, since only highly specialized organisms can effectively degrade them in the ocean.'Lentimonas'-a marine microorganism from the Verrucomicrobia phylum-has >200 different glycoside hydrolase and sulfatase enzymes enabling digestion of the algal polysaccharide fucoidan, which was thought to be a recalcitrant source of carbon in our oceans.