Department of Marine Chemistry, Zhejiang Ocean University, Zhoushan, China.
ABI Group of GPM Project, Zhejiang Ocean University, Zhoushan, China.
Antonie Van Leeuwenhoek. 2021 Jul;114(7):1091-1106. doi: 10.1007/s10482-021-01580-0. Epub 2021 Apr 24.
Marine phycosphere harbors unique cross-kingdom associations with enormous ecological significance in aquatic ecosystems as well as relevance for algal biotechnology industry. During our investigating the microbial composition and bioactivity of marine phycosphere microbiota (PM), a novel lightly yellowish and versatile bacterium designated strain AM1-D1 was isolated from cultivable PM of marine dinoflagellate Alexandrium minutum amtk4 that produces high levels of paralytic shellfish poisoning toxins (PSTs). Strain AM1-D1 demonstrates notable bioflocculanting bioactivity with bacterial exopolysaccharides (EPS), and microalgae growth-promoting (MGP) potential toward its algal host. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain AM1-D1 was affiliated to the members of genus Sulfitobacter within the family Rhodobacteraceae, showing the highest sequence similarity of 97.9% with Sulfitobacter noctilucae NB-68, and below 97.8% with other type strains. The complete genome of strain AM1-D1 consisted of a circular 3.84-Mb chromosome and five circular plasmids (185, 95, 15, 205 and 348 Kb, respectively) with the G+C content of 64.6%. Low values obtained by phylogenomic calculations on the average nucleotide identity (ANI, 77.2%), average amino acid identity (AAI, 74.7%) and digital DNA-DNA hybridization (dDDH, 18.6%) unequivocally separated strain AM1-D1 from its closest relative. The main polar lipids were identified as phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, diphosphatidylglycerol, one unidentified phospholipid and one unidentified lipid. The predominant fatty acids (> 10%) were C ω7c, C cyclo ω8c and C. The respiratory quinone was Q-10. The genome of strain AM1-D1 was predicted to encode series of gene clusters responsible for sulfur oxidation (sox) and utilization of dissolved organic sulfur exometabolites from marine dinoflagellates, taurine (tau) and dimethylsulfoniopropionate (DMSP) (dmd), as well as supplementary vitamin B (cob), photosynthesis carotenoids (crt) which are pivotal components during algae-bacteria interactions. Based on the evidences by the polyphasic characterizations, strain AM1-D1 represents a novel species of the genus Sulfitobacter, for which the name Sulfitobacter alexandrii sp. nov. is proposed. The type strain is AM1-D1 (= CCTCC 2017277T = KCTC 62491).
海洋菌席与水生生态系统中具有巨大生态意义的跨界共生体有关，同时也与藻类生物技术产业相关。在研究海洋菌席微生物群落（PM）的微生物组成和生物活性时，我们从能够产生高水平麻痹性贝类毒素（PSTs）的海洋甲藻亚历山大藻 amtk4 的可培养 PM 中分离出一种新型的浅黄色多功能细菌，命名为菌株 AM1-D1。菌株 AM1-D1 具有显著的细菌胞外多糖（EPS）絮凝活性和促进微藻生长（MGP）的潜力，可促进其藻类宿主的生长。基于 16S rRNA 基因序列的系统发育分析表明，菌株 AM1-D1 属于红杆菌科硫杆菌属的成员，与硫杆菌属 noctilucae NB-68 的序列相似性最高，为 97.9%，与其他模式菌株的序列相似性低于 97.8%。菌株 AM1-D1 的全基因组由一个 3.84-Mb 的环状染色体和五个环状质粒（分别为 185、95、15、205 和 348 Kb）组成，GC 含量为 64.6%。基于平均核苷酸同一性（ANI，77.2%）、平均氨基酸同一性（AAI，74.7%）和数字 DNA-DNA 杂交（dDDH，18.6%）的系统基因组计算得出的低值，明确将菌株 AM1-D1 与其最接近的亲缘关系区分开来。主要的极性脂为磷脂酰甘油、磷脂酰乙醇胺、磷脂酰胆碱、双磷脂酰甘油、一种未鉴定的磷脂和一种未鉴定的脂。主要脂肪酸（>10%）为 C ω7c、C 环 ω8c 和 C。呼吸醌为 Q-10。菌株 AM1-D1 的基因组预测编码一系列基因簇，负责海洋甲藻硫氧化（sox）和利用溶解有机硫外代谢物（如牛磺酸（tau）和二甲基磺丙酯（DMSP）（dmd）），以及补充维生素 B（cob）、光合作用类胡萝卜素（crt），这些都是藻类-细菌相互作用的关键组成部分。基于多相特征的证据，菌株 AM1-D1 代表硫杆菌属的一个新种，因此提议将其命名为亚历山大硫杆菌（Sulfitobacter alexandrii）。模式菌株为 AM1-D1（=CCTCC 2017277T=KCTC 62491）。
