中文摘要：

于2005年2月在太湖不同营养水平湖区采集水样,直接提取水样的总DNA,以细菌16SrDNA通用引物进行V3区PCR扩增,产物经DGGE（变性凝胶梯度电泳）分离后,获得水体细菌群落的16SrDNA指纹图谱;并运用FDC（表面荧光直接计数）方法对细菌丰度进行了测定.结果表明,水体中细菌的群落结构随着水体富营养化程度的改变产生明显变化,细菌数量呈现随水体营养水平增加而上升的趋势,营养水平较低的湖心区细菌数量仅为2.87×10^6cells·mL^-1,超富营养化的五里湖区水体中,细菌数量高达5.92×10^6cells·mL^-1;细菌群落多样性随水体营养水平增加呈现显著的下降趋势,在超富营养化的1#、2#采样位点,细菌DGGE主要条带数量仅为23条,在沉水植物丰富区（贡湖湾）细菌DGGE主要条带数量达33条.PCA（主成分分析）的聚类结果表明,太湖水体中不同营养水平下的细菌群落多样性可大致归为3种类型,超富营养化的五里湖区水体细菌群落结构与梅梁湾及汞湖湾存在明显不同,可以大体归为超富营养类型、藻型湖区及草型湖区类型3种.此结果反映了水体富营养化过程中,由于营养物质的增加,促进了某些类群微生物的大量繁殖,水体中微生物的生物量显著增加;生态环境条件的恶化,造成了微生物多样性的下降,这可能导致原本稳定的水生态系统脆弱化.

英文摘要：

Water samples from the algal bloom area to the macrophyte-dominated area of Lake Taihu were collected in Feb. 2005. Culture-independent 16S rDNA-DGGE fingerprinting and FDC methods were used to reveal the community structure and changing quantities of the bacteria in the eutruphying lake. The results showed that the bacterial community structure changed with different nutrition levels. The bacterial abundance increased with nutrition levels. In water samples from the center of Lake Taihu, there were only about 2.87 ×10^6cells, mL · ^-1, while at stations 1 ^# , 2^# , near the northeast shore, the bacteria increased to about 5.92 ×10^6 cells· mL^-1. However, the number of DGGE bands in the water samples declined with the increase of the nutrition level. A total of 23 major bands were found at stations 1^# in the algal bloom area, while 33 major bands were recorded at stations 7^# , 8^# in the macrophyte-dominated area. PCA analysis of the DGGE profiles showed that the bacteria in the eight water samples belonged to three groups. The bacterial community structure was dependent on the location and the nutrient level. This study demonstrated that with the increase of water eutrophication, the biomass of bacteria increased and the diversity of the bacterial community decreased.