| ZENG Yinxin. 2019. Phylogenetic diversity of dimethylsulfoniopropionate-dependent demethylase gene dmdA in distantly related bacteria isolated from Arctic and Antarctic marine environments. Acta Oceanologica Sinica, 38(8):64－71 |
| Phylogenetic diversity of dimethylsulfoniopropionate-dependent demethylase gene dmdA in distantly related bacteria isolated from Arctic and Antarctic marine environments |
| 南、北极海洋不同种类细菌分离株中DMSP-依赖型脱甲基酶基因dmdA的系统发育多样性 |
| Received:February 23, 2018 |
| DOI：10.1007/s13131-019-1393-7 |
| Key words:dimethylsulfoniopropionate-dependent demethylase gene (dmdA) horizontal gene transfer marine bacteria Arctic Antarctic |
| 中文关键词: DMSP-依赖型脱甲基酶基因（dmdA） 水平基因转移 海洋细菌 北极 南极 |
| 基金项目:The National Natural Science Foundation of China under contract No. 41476171; the Chinese Polar Environment Comprehensive Investigation and Assessment Program under contract No. CHINARE04-01. |
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| Abstract: |
| Dimethylsulfoniopropionate (DMSP) is mainly produced by marine phytoplankton as an osmolyte, antioxidant, predator deterrent, or cryoprotectant. DMSP is also an important carbon and sulfur source for marine bacteria. Bacteria may metabolize DMSP via the demethylation pathway involving the DMSP demethylase gene (dmdA) or the cleavage pathway involving several different DMSP lyase genes. Most DMSP released into seawater is degraded by bacteria via demethylation. To test a hypothesis that the high gene frequency of dmdA among major marine taxa results in part from horizontal gene transfer (HGT) events, a total of thirty-one bacterial strains were isolated from Arctic Kongsfjorden seawater in this study. Analysis of 16S rRNA gene sequences showed that, except for strains BSw22118, BSw22131 and BSw22132 belonging to the genera Colwellia, Pseudomonas and Glaciecola, respectively, all bacteria fell into the genus Pseudoalteromonas. DmdA genes were detected in five distantly related bacterial strains, including four Arctic strains (Pseudoalteromonas sp. BSw22112, Colwellia sp. BSw22118, Pseudomonas sp. BSw22131 and Glaciecola sp. BSw22132) and one Antarctic strain (Roseicitreum antarcticum ZS2–28). Their dmdA genes showed significant similarities (97.7%-98.3%) to that of Ruegeria pomeroyi DSS–3, which was originally isolated from temperate coastal seawater. In addition, the sequence of the gene transfer agent (GTA) capsid protein gene (g5) detected in Antarctic strain ZS2–28 exhibited a genetically closely related to that of Ruegeria pomeroyi DSS–3. Among the five tested strains, only Pseudomonas sp. BSw22131 could grow using DMSP as the sole carbon source. The results of this study support the hypothesis of HGT for dmdA among taxonomically heterogeneous bacterioplankton, and suggest a wide distribution of functional gene (i.e., dmdA) in global marine environments. |
| 中文摘要: |
| 二甲基巯基丙酸内盐（DMSP）主要是由海洋浮游植物生成，可作为胞内渗透调节剂、抗氧化剂、捕食者威慑物、或抗冻剂。DMSP对于海洋细菌而言也是一种重要的碳源和硫源。细菌可以通过涉及DMSP脱甲基酶基因（dmdA）的脱甲基途径、或涉及7种DMSP裂解酶基因的裂解途径对DMSP进行分解代谢。释放到海水中的大多数DMSP是被细菌通过脱甲基途径降解。在主要的海洋细菌种类中存在着较高的dmdA基因频率，这可能部分归功于该基因的水平基因转移（HGT）行为。为了验证这一假设，课题组从北极王湾分离获得了31株细菌。16S rRNA基因序列分析结果表明，除了菌株BSw22118、BSw22131、以及BSw22132分别属于科尔韦尔氏菌属、假单胞菌属、以及冰川菌属之外，其余细菌都属于假交替单胞菌属。在5株亲缘关系较远的不同细菌株中，包括分离自北极的假交替单胞菌BSw22112、科尔韦尔氏菌BSw22118、假单胞菌BSw22131、冰川菌BSw22132和分离自南极的玫瑰柠檬形菌ZS2-28，均检测到dmdA基因。这些dmdA基因与来自温带近岸海水中的鲁杰氏菌DSS-3的dmdA基因具有很高的序列相似性（97.7 %–98.3 %）。此外，在南极玫瑰柠檬形菌ZS2-28中检测到的基因转移因子（GTA）核衣壳蛋白基因g5与鲁杰氏菌DSS-3的g5基因也具有很近的亲缘关系。在这5株极地分离菌中，只有假单胞菌BSw22131能够以DMSP作为唯一碳源进行生长。本次研究的结果支持了不同种类的浮游细菌中存在dmdA基因的水平基因转移这一假说，同时也表明在全球海洋环境中存在如dmdA等功能基因的广泛分布。 |
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