摘要 : This study focuses on the community structure of aggregated bacteria in Lake Baikal and relationships with free-living bacteria. Fluorescent in situ hybridization (FISH) methods were used in samples of bacteria taken in April, 200... 展开 This study focuses on the community structure of aggregated bacteria in Lake Baikal and relationships with free-living bacteria. Fluorescent in situ hybridization (FISH) methods were used in samples of bacteria taken in April, 2001. Bacterial counts of free-living bacteria by DAPI staining ranged from 0.2 x 10 super(6) to 3.2 x 10 super(6) cells . ml super(-1), decreasing with depth, whereas aggregated bacterial numbers dramatically increased with depth, ranging from 0.4 to 3.3 x 10 super(4) cells ml super(-1). Ratios of EUB probe binding cells to DAPI counts ranged from 52.3 to 74.1% in free-living bacteria, and from 39.6 to 66.7% in aggregated bacteria, respectively. Community composition of aggregated bacteria was very different from free-living bacteria, especially at the 25 m depth where highest phytoplankton numbers were observed. The vertical profile of aggregated bacteria community was very characteristic. beta -Proteobacteria increased with depth down to 100 m. At 250 m, gamma -Proteobacteria was 44% of DAPI bound cells, while other groups were less than 1%. We conclude that community structures of free-living and aggregated bacteria were different, and they may sustain the ecosystem in independent ways. 收起