Bacterial–algal interactions strongly influence marine ecosystems. Bacterial communities in cultured dinoflagellates of the family Symbiodiniaceae have been characterized by metagenomics. However, little is known about whole‐genome analysis of marine bacteria associated with these dinoflagellates. We performed in silico analysis of four bacterial genomes from cultures of four dinoflagellates of the genera Symbiodinium, Breviolum, Cladocopium and Durusdinium. Comparative analysis showed that the former three contain the alphaproteobacterial family Parvibaculaceae and that the Durusdinium culture includes the family Sphingomonadaceae. There were no large genomic reductions in the alphaproteobacteria with genome sizes of 2.9–3.9 Mb, implying they are not obligate intracellular bacteria. Genomic annotations of three Parvibaculaceae detected the gene for diacetylchitobiose deacetylase (Dac), which may be involved in the degradation of dinoflagellate cell surfaces. They also had metabolic genes for dissimilatory nitrate reduction to ammonium (DNRA) in the nitrogen (N) cycle and cobalamin (vitamin B12) biosynthetic genes in the salvage pathway. Those three characters were not found in the Sphingomonadaceae genome. Predicted biosynthetic gene clusters for secondary metabolites indicated that the Parvibaculaceae likely produce the same secondary metabolites. Our study suggests that the Parvibaculaceae is a major resident of Symbiodiniaceae cultures with antibiotics.

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共生科基因组组装中细菌基因组的功能分析

细菌-藻类相互作用强烈影响海洋生态系统。共生甲藻科培养的甲藻中的细菌群落已通过宏基因组学进行了表征。然而，人们对与这些甲藻相关的海洋细菌的全基因组分析知之甚少。我们对来自该属的四种甲藻培养物的四种细菌基因组进行了计算机分析共生藻属,短叶草属,枝叶属和杜鲁斯丁属。比较分析表明，前三者均含有α变形菌科Parvibaculaceae，且杜鲁斯丁属文化包括鞘氨醇单胞菌科。基因组大小为 2.9-3.9 Mb 的 α-变形菌没有大幅基因组减少，这意味着它们不是专性细胞内细菌。三种小杆科植物的基因组注释检测到二乙酰壳二糖脱乙酰酶 (Dac) 基因，该基因可能参与甲藻细胞表面的降解。它们还具有氮 (N) 循环中硝酸盐异化还原为铵 (DNRA) 和钴胺素（维生素 B）的代谢基因12）挽救途径中的生物合成基因。在鞘氨醇单胞菌科基因组中没有发现这三个特征。预测的次生代谢物生物合成基因簇表明，小杆科可能产生相同的次生代谢物。我们的研究表明，小杆科是抗生素共生科培养物的主要居民。