【作者】 张东声；

【导师】 吴敏；

【作者基本信息】 浙江大学 ， 微生物， 2011， 博士

【摘要】 长江是我国流入东海的最大河流,平均年入海径流量为9.28×1011m3,占流入东海总径流量的84.4%,其中75%的径流量在4-9月丰水期时注入东海,并向东呈扇形扩展。长江口及其邻近海域在长江巨量径流、复杂流系结构和特殊的地形的共同影响下呈现出独特的“冲淡水转向”、“上升流”、“锋面迁移”等诸多现象,这些海流和水团又直接或间接的影响该海域温度、盐度、营养盐等理化因子,形成独特的生态环境特征。微生物即是生产者又是分解者,在海洋生态系统扮演重要角色,在生物地球化学循环中也具有重要意义。本论文针对长江口海域这一典型的河口生态系统,将微生物学、分子生物学和生态学等研究手段相结合,研究该海域微生物的时空分布规律、多样性,并根据多项分类学原则对具有代表性的微生物菌种进行详细研究。首先,长江口及其邻近海域水体细菌丰度具有明显的季节变化,平均丰度为春季>秋季>夏季>冬季。各个季节细菌丰度呈现出不同的水平和垂直分布特征：水平方面,春、秋季由长江口向外海逐渐升高,夏季南北两侧细菌丰度较高、中部海区较低,且底层具有大面积的低值区,冬季细菌丰度高值区位于舟山群岛东北；垂直方面、春季、秋季和冬季细菌丰度垂直分布较均匀,而夏季层化现象明显。病毒丰度也具有明显的季节变化,但各个水深的季节变化并不一致,病毒的水平特征为春、秋季由河口向外海升高,夏、冬季由河口向外海降低,垂直分布与细菌一致。从各环境因子与细菌、病毒的相关分析来看,温度、溶解氧和营养盐等环境因子与细菌丰度均没有明显的相关性,盐度在春季和秋季与细菌丰度之间呈显著正相关,可能对细菌分布有一定影响。此外病毒与细菌具有极其显著的正相关性,细菌丰度对病毒丰度可能有较强的影响。沉积物细菌丰度的季节变化为秋季>春季>夏季>冬季,水平分布方面春、冬季河口近岸区较高,夏、秋季外海陆架区较高。沉积物中的有机物含量和沉积物底质是影响细菌丰度的主要原因。其次,长江口及其邻近海域沉积物中的细菌具有较高的多样性,16SrRNA基因分析表明主要包括变形菌(Proteobacteria)、酸杆菌门(Acidobacteria)、硬壁菌门(Firmicutes)、放线菌门(Actinobacteria)、硝化螺旋菌门(Nitrospirae)、拟杆菌门(Bacteroidetes)、疣微菌门(Verrucomicrobia)、浮霉菌门(Planctomycetes)、绿弯菌门(Chloroflexi)、异常球菌-栖热菌门(Deinococcus-Thermus)和热袍菌门(Thermotogae),变形菌是该海域沉积物细菌的优势类群。不同环境沉积物细菌的多样性和群落结构有明显差异,长江河口内以陆源或淡水生境的细菌种类为主,东海陆架区则以海洋环境的种类为主,长江口门区则同时包含了海-陆(咸-淡水)两类环境的细菌16SrRNA基因序列。最后,从浙江近海沉积物中分离到两株嗜盐疑似新种Y215T和Y226T,并进行了多相分类学研究。结果表明,这两株菌株细菌为革兰氏阴性细菌,无鞭毛,在不同的培养条件下表现出不同的形态特征,主要脂肪酸成分分别为菌株Y215T：iso-C15：0,iso-C17：1ω9C,iso-C17：0,iso-C11：03-OH,C16：0,iso-C11：0和C18：1ω7c；菌株Y226T：iso-C15：0,iso-C11：03-OH,iso-C17：1ω9c,iso-C11：0和iso-C17：0；G+C mol%分别为54%和56.7%,与16S rRNA基因相似性最高的标准菌株杂交复兴率均显著低于70%这一微生物新种准则,系统发育分析则显示在Microbulbifer世系中分别处于不同的分支上。建议定义上述两株菌株为产微球茎菌属(Microbulbifer)的两个新的分类单元,命名为：海洋微球茎菌Microbulbifer marinus (ma.ri’nus. L. masc. adj. marinus, of the sea, marine)和乐清湾微球茎菌Microbulbifer yueqingensis (yue.qin.gen’sis. N.L. masc. adj. yueqingensis, belonging to Yueqing bay, the Chinese name of the Yueqing bay).更多还原

【Abstract】 The Changjiang River (historically called the Yangtze River) is the third-largest river in the world, with a huge water discharge of9.28x1011m3per year, equivalent to84.4%of the total riverine discharge of the East China Sea. The Changjiang estuary, which is located offshore from the mouth of the Changjiang River, is an area where freshwater, Changjiang Diluted Water (CDW), is mixed with the Taiwan Warm Current (TWC) from the south and Yellow Sea Coastal Water (YSCW) from the north. Because it is the interface of land, freshwater and marine environments, this region is extremely complicated and dynamic. Bacteria, producer and decomposer, plays an important role in marine ecosystem and are recognized as important agents in biogeochemical processes in the earth. In this thesis, we aimed to study distribution and diversity of marine bacteria in the Changjiang Estuary and adjacent areas.Firstly, we studied temporal and spatial distribution of bacteria and virus in the Changjiang estuary and adjacent areas. Bacteria abundance in seawater showed a clearly seasonal variability, with an order of spring> autumn> summer> winter for average bacteria abundance. Horizontal distributions were different in the four seasons. In spring and autumn, bacteria abundance was low in river mouth and coastal areas but higher in offshore areas. In summer, bacteria abundance were higher in north and south areas, but lower in central part, furthermore, there was a large low abundance areas in bottom in south of31°N. In winter, bacteria abundance were higher in east of Zhoushan Islands. Vertical distribution were similar in spring, autumn and winter, that bacteria abundance in all depth(surface,10m, bottom) were quite similar, however, in summer, bacteria abundance decreased with depth which indicated a strong stratification. Virus abundance also had a seasonally variability, despite which were not the same in different depth. There were two opposite horizontal distribution styles for virus abundance, in spring and autumn, virus abundance were lower in river mouth and coastal areas but higher in offshore, while in summer and winter, virus abundance were higher in river mouth and coastal areas but lower in offshore. A positive relationship was found between salinity and bacteria abundance in spring and autumn, but no obvious correlation between other environmental factors (eg. temperature, dissolved oxygen, nutrients) and bacteria abundance were found. Furthermore, virus abundance showed a significant positive relationship with bacteria abundance. The order of sedimentary heterobacteria abundance in the four seasons was autumn> spring> summer> winter. In spring and winter, sedimentary heterobacteria abundance was higher in coastal areas, while in summer and autumn, it was higher in offshore areas. Concentration of organic matter and substrate of sediment could be the two main factors influencing distribution of sedimentary heterobacteria abundance.Secondly, diversity of bacteria in the Changjiang estuary and adjacent areas sediment were studied. Phylogenetic analyses were performed on the prokaryotic community and diversity based on the16S rRNA, bacterial phyla detected included the Proteobacteria, Acidobacteria, Firmicutes, Actinobacteria, Bacteroidetes, Planctomycetes, Nitrospirae, Chloroflexi, Verrucomicrobia, Deinococcus-Thermus, Thermotogae. Proteobacteria was the dominant group in study area. However, community structure was quite different in all three kinds of sediment environments. Most clones obtained from the inlet of the Changjiang river related to uncultured bacteria from terrestrial and freshwater environment, clones obtained from East China Sea shelf related to uncultured bacteria from marine environment. Site in river mouth showed a higher diversity than the other two sites and a more compatible environment resource including both marine and terrestrial16S rRNA sequences.Finally, a systematic study had been conducted on the taxonomy of two strains isolated from coastal sediment of Zhejiang province in accordance with the principle of polyphasic taxonomy. The results showed that both the two strains were gram-negative and non-motile, they showed different cell form in different culture conditions. The predominant cellular fatty acids are iso-C15:0, iso-C17:1ω9c, iso-C17:0, iso-C11:0.3-OH, C16:0, iso-C11:0and C18:1ω7c for strain Y215T and iso-C15:0, iso-C11:03-OH, iso-C17:1ω9c, iso-C11:0and iso-C17:0for strain Y226T. The G+C content was54mol%and56.7%, respectively. The DNA-DNA relatedness between the two strains and type strains were significantly lower than that accepted as the phylogenetic definition of a species. On the basis of their distinct taxonomic characteristics, the two isolated strains represent two novel species of the genus Microbulbifer, for which the names Microbulbifer marinus sp. nov. and Microbulbifer yueqingensis sp. nov. are proposed. The type strains are Y215T (=CGMCC1.10657T=JCM17211T) and Y226T (=CGMCC1.10658T=JCM17212T), respectively.更多还原