DYNAMICS OF DETRITUS-ATTACHED AND FREE-LIVING BACTERIA DURING DECOMPOSITION OF PHRAGMITES COMMUNIS POWDER IN SEAWATER

Abstract

To clarify the ecological characteristics of detritus-attached bacteria as compared with free-living bacteria, a model system consisted of seawater, powder of Phragmites communis as detrital particles, and natural bacterial population was incubated for 116 days. Fractionation of deteritus-attached and free-living bacteria was made by filtration through a Nuclepore filter with 5 μm porosity. Loosely detritus sorbed bacteria were separated from detritus by treatment with a Wahring blender before the filtration and included in free-living bacteria. All number ratios of glucose, cellobiose-, starch- and casein-decomposing bacteria to viable heterotrophic bacteria were higher for attached bacteria than those for free-living bacteria during almost all incubation period. The composition of colony types was different between attached and free-living bacteria. These results suggest that the flora and abilities to decompose organic substances were different between these two bacterial populations. The number ratio of free-living bacteria to attached bacteria for each colony type was markedly different between two dominant colony types. Pure culture experiments using the two bacterial species isolated from above two colony types indicated that this difference may be due to the difference in their intrinsic attachment properties to detritus.