Elucidation of the microbial community structure within a laboratory-scale activated sludge process using molecular techniques

Abstract

Microbial community structures were analysed in activated sludge samples from the anoxic and aerobic zones of a labora tory-scale modified Ludzack-Ettinger (MLE) system. Analyses were performed using fluorescent in situ hybridisation (FISH) and denaturing gradient gel electrophoresis (DGGE). The r-RNA targeted oligonucleotide probes used for FISH targeted the alpha, beta and gamma subclasses of the gram-negative family Proteobacteria , the high G+C content gram-positive bacterium of the actinomycetes branch and the total Eubacteria present. It was found that approximately 75 to 80% of total cells were detected with the DNA specific fluorochrome DAPI, hybridised with a specific eubacterial probe for the anoxic and aerobic zones. Results confirmed the dominance of the alpha and gamma subclasses of the Proteobacteria in the anoxic zone whilst the aerobic zone was dominated with the beta subclass of the Proteobacteria . The high G+C content bacterium represented the least dominant species present within each of the two zones.

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