Difference in bacterial floras among different size fractions of suspended particles in a hypertrophic pond.

The bacterial floras in four size fractions (>35 m, 35-5 m, 5-1 m, and < 1 m) of suspended particles separated by size fractionation from the surface water of Himon-ya Pond, a Hypertrophic pond in Tokyo, were investigated from August 1978 to January 1979. The bacterial flora in the >35 m fraction (bacteria associated mainly with the mucilage of Microcystis colonies) showed a simple generic composition during the Micro-cystis bloom, and was almost dominated by the bacteria tentatively identified as Pseudomonas-like, which were Gram-negative, strictly aerobic, catalase weakly positive, oxidase negative, colorless or pinkish pigmented, and slightly irregular rods with a single polar flagellum. In the 35-5 m and 5-1 m fractions (bacteria associated with various kinds of phytoplankton, detritus, and clay particles), bacterial populations showed a more diversified bacterial flora than that in the >35 m fraction. The bacterial flora in the <1 m fraction (free-living bacteria) was dominated by one or two genera such as Pseudomonas, Flavobacterium, Moraxella, Caulobacter, and Acinetobacter at each sampling time. These results suggest the existence of different bacterial floras among different size fractions of suspended particles in the pond water.