College of Food Science and Engineering, Ocean University of Chinagrid.4422.0, Qingdao, China.
Laboratory for Marine Drugs and Bioproducts of Qingdao National Laboratory for Marine Science and Technology, Qingdao, China.
Appl Environ Microbiol. 2022 Sep 22;88(18):e0110022. doi: 10.1128/aem.01100-22. Epub 2022 Aug 29.
Carbohydrate-active enzymes are important components of the polysaccharide metabolism system in marine bacteria. Carrageenase is indispensable for forming carrageenan catalytic pathways. Here, two GH16_13 carrageenases showed likely hydrolysis activities toward different types of carrageenans (e.g., κ-, hybrid β/κ, hybrid α/ι, and hybrid λ), which indicates that a novel pathway is present in the marine bacterium Flavobacterium algicola to use κ-carrageenan (KC), ι-carrageenan (IC), and λ-carrageenan (LC). A comparative study described the different features with another reported pathway based on the specific carrageenans (κ, ι, and λ) and expanded the carrageenan metabolic versatility in . A further comparative genomic analysis of carrageenan-degrading bacteria indicated different distributions of carrageenan metabolism-related genes in marine bacteria. The crucial core genes encoding the GH127 α-3,6-anhydro-d-galactosidase (ADAG) and 3,6-anhydro-d-galactose (d-AHG)-utilized cluster have been conserved during evolution. This analysis further revealed the horizontal gene transfer (HGT) phenomenon of the carrageenan polysaccharide utilization loci (CarPUL) from to other bacterial phyla, as well as the versatility of carrageenan catalytic activities in marine bacteria through different metabolic pathways. Based on the premise that the specific carrageenan-based pathway involved in carrageenan use by Flavobacterium algicola has been identified, another pathway was further analyzed, and it involved two GH16_13 carrageenases. Among all the characterized carrageenases, the members of GH16_13 accounted for only a small portion. Here, the functional analysis of two GH16_13 carrageenases suggested their hydrolysis effects on different types of carrageenans (e.g., κ, hybrid β/κ, hybrid α/ι-, and hybrid λ-), which led to the identification of another pathway. Further exploration enabled us to elucidate the novel pathway that metabolizes KC and IC in successfully. The coexistence of these two pathways may provide improved survivability by in the marine environment.
碳水化合物活性酶是海洋细菌多糖代谢系统的重要组成部分。卡拉胶酶对于形成卡拉胶催化途径是不可或缺的。在这里，两种 GH16_13 卡拉胶酶对不同类型的卡拉胶（例如 κ-、混合 β/κ-、混合 α/ι-和混合 λ-）表现出可能的水解活性，这表明海洋细菌 Algicola 中存在一种新的途径来利用 κ-卡拉胶（KC）、ι-卡拉胶（IC）和 λ-卡拉胶（LC）。一项比较研究描述了另一种基于特定卡拉胶（κ、ι 和 λ）的途径的不同特征，并扩展了卡拉胶代谢的多样性。对降解卡拉胶的细菌的进一步比较基因组分析表明，海洋细菌中卡拉胶代谢相关基因的分布不同。编码 GH127 α-3,6-脱水-d-半乳糖醛酸酶（ADAG）和 3,6-脱水-d-半乳糖（d-AHG）利用簇的关键核心基因在进化过程中得到了保守。这项分析进一步揭示了卡拉胶多糖利用基因座（CarPUL）从到其他细菌门的水平基因转移（HGT）现象，以及海洋细菌通过不同代谢途径对卡拉胶催化活性的多功能性。基于已确定的 Algicola 中涉及卡拉胶利用的特定卡拉胶途径的前提，进一步分析了另一种途径，该途径涉及两种 GH16_13 卡拉胶酶。在所有表征的卡拉胶酶中，GH16_13 的成员仅占很小一部分。在这里，两种 GH16_13 卡拉胶酶的功能分析表明它们对不同类型的卡拉胶（例如 κ-、混合 β/κ-、混合 α/ι-和混合 λ-）的水解作用，这导致了另一种途径的确定。进一步的探索使我们能够阐明成功代谢 KC 和 IC 的新途径。这两种途径的共存可能通过 Algicola 在海洋环境中的生存能力得到提高。
