实验海洋生物学重点实验室知识库

    极端生存环境使深海热液区微生物具有十分独特的生理生化特征和能量代谢途径，这些微生物不仅是巨大的新型功能基因和新型生物活性物质资源库，同时也对深海生物地球化学过程有着巨大的影响，因此对深海热液微生物的研究十分必要。本文的第一部分对来自冲绳海槽热液区的一株细菌 Exiguobacterium sp.HVEsp1进行了研究。HVEsp1分离自冲绳海槽深海热液沉积物，能在 50 ℃生长，游动能力强，具有多种重金属和抗生素抗性。HVEsp1 的基因组大小为 2838499 bp，G+C 含量为 48.2%，包含 2948 个编码序列。基因组序列分析显示了大量与细胞运动、重金属抗性、抗生素抗性和耐热相关基因。通过与其亲缘关系最近的菌株Exiguobacterium sp. AT1b 进行比较基因组分析发现，HVEsp1 的基因组中移动元件数量丰富，它们可能在细菌通过基因水平转移获得有利基因的过程中发挥重要作用。这些结果加深了我们对深海热液细菌适应极端环境机制的了解，也为以后的深入研究奠定了基础。

    在本文第二部分中， 我们从分离自热液沉积物和大型生物样品的细菌中筛选了出一株致病菌株Bacillus sp. SR-52。 分析发现， SR-52 对大菱鲆和小鼠有较高致死率。进一步研究发现 SR-52 在大菱鲆血清和小鼠血清中具高存活率，与 SR-52孵育后的大菱鲆血清溶血活性和杀菌活性均显著降低，说明 SR-52 能激活宿主血清中的补体系统， 同时也能够抵抗补体的杀伤作用。大菱鲆体内感染实验表明，SR-52 能侵入肝、脾和肾， 且随感染时间延长组织中细菌数量增加， 说明细菌能在宿主组织内繁殖。 这些研究结果对于深海致病菌的致病机制研究奠定了基础，也为深海开采活动提了指导。

    Extreme environmental conditions support a variety of microbes which are characterized with unique physiological and biochemical properties and energy metabolisms. These microbes are not only huge reservoirs for novel functional genes and bioactive substances, but of vital importance in deep-sea biogeochemical process. Therefore, it’s necessary to do researches on deep-sea hydrothermal microbes. Studies on microbial adaption mechanisms to deep-sea hydrothermal vent environments are rare. In this study, we studied a bacteria strain, named Exiguobacterium sp. HVEsp1, isolated from an active hydrothermal vent at Okinawa Trough. HVEsp1 grew at 50 °C and exhibited a strong swimming capacity and resistance against multiple heavy metals and antibiotics. The high-quality draft genome sequence indicated that the genome of HVEsp1 is 2838499 bp with an average G+C content of 48.2% and contains 2948 predicted coding sequences. The genome is abundant with genes associated with cell motility, heavy metal resistance, drug resistance and thermo-tolerance. By comparing with the genome of its closest relative Exiguobacterium sp. AT1b, HVEsp1 was found to possess large amounts of mobile elements, which can enable the bacteria to gain favorable genes by horizontal gene transfer. These results shed light on the mechanism of bacterial adaption to the extreme environment in deep-sea hydrothermal vent.
     In the second part of this study, we screened a pathogenic strain Bacillus sp. SR-52 from bacteria isolated from deep-sea hydrothermal vent samples. The results showed that SR-52 could induce mortality in turbot (Scophthalmus maximus) and mice (Mus musculus). When incubated with turbot and mouse sera, SR-52 exhibited high survival rates (96.15% and 72.05 %, respectively). SR-52-incubated turbot serum exhibited significance reduced hemolytic activity and bactericidal activity. These results indicated that SR-52 could activate the complement in turbot serum, but it could also resist the killing effect of the serum. In vivo infection experiment showed that SR-52 could disseminate and colonized in liver, spleen and kidney of turbots. These results provided a basis for further study of the pathogenicity of deep-sea bacterial pathogens.