Bacterial activity and community composition in stream water and biofilm from an urban river determined by fluorescent in situ hybridization and DGGE analysis

Physiologic activity and community structure of planktonic and biofilm microbial communities in an urban river were analyzed using 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) staining, fluorescent in situ hybridization (FISH) and denaturing gradient gel electrophoresis (DGGE) analysis of polymerase chain reaction (PCR)-amplified 16S rDNA fragments. Respiring bacteria estimated by CTC reduction were higher in biofilms (20%) than in stream water samples (12%). FISH analysis revealed that bacterial populations in both stream water and biofilms were dominated by beta-Proteobacteria and Cytophaga-Flavobacterium cluster. Microbial community changes determined by multidimensional scaling analysis from DGGE patterns showed that microbial community structures in biofilms matured within 3-7 days of their formation and did not change further, while those in stream water changed continuously.