BETWEEN-SITE COMPARISON OF FRESH-WATER BACTERIOPLANKTON BY DNA HYBRIDIZATION

Natural assemblages of freshwater bacterioplankton in enriched lowland rivers had greater cell-specific metabolic activity than those in gra vel-pit ponds. Similarly, cell-specific activity and mean cell size in calcareous headstreams tended to be greater than in intermittently-ac id headstreams on millstone grit. DNA was extracted and purified from bacterioplankton assemblages, and between-site comparisons were made i n terms of percentage similarity as indicated by DNA hybridization. Cl uster analysis, using percentage-similarity matrices, placed bacteriop lankton assemblages from different site types into distinct groups. Th is suggested that between-site physiological differences were related to intrinsically different bacterial composition rather than to differ ent physiological response to different environmental conditions by es sentially similar bacterial assemblages.