抄録
Bacterial numbers and floras in the water and sediment of subtropical Lakes Phewa, Begnas, and Rupa in the Pokhara Valley, Nepal, were surveyed in late monsoon season. In the water column at the deepest part of Lakes Phewa, Begnas, and Rupa, total bacteria estimated by the acridine orange direct count (AODC) method changed in the range of 1.1-2.4×106, 1.7-2.4×106, and 3.2-3.5×106 cells/ml, respectively, and heterotrophic bacteria estimated by the spread plate method changed in the range of 2.5-18×103, 2.0-4.0×103, and 6.9-14×103 CFU (colony-forming units)/ml, respectively. The distribution pattern of free-living and attached heterotrophic bacteria, size-fractionated with a 3.0μm Nuclepore filter, throughout the water column differed among the three lakes. The total and heterotrophic bacteria in the water at inlet were in the orders of 104-105cells/ml and 103CFU/ml, respectively, and those in the water at outlet showed a similar number to those in the surface water at each deepest part. The number of heterotrophic bacteria in the sediment at the deepest part was not different among the lakes and in the range of 5.9-8.9×105 CFU/cm3 of wet sediment. All of 178 isolates purified from the three lakes, 64 from the water and 114 from the sediment, were identified to generic level. Only 20% of bacteria isolated from the water were purified, and most of those isolates belonged to Pseudomonas, Flavobacterium, and coryneforms. On the other hand, the bacterial floras in the sediment of the three lakes were dominated by Bacillus.
