A culture-independent approach for studying microbial diversity in aerobic granules

This study reports the use of ribosomal-based molecular techniques to study the microbial diversity in aerobic granules. Aerobic granules at different growth stages (young, mature and old) were obtained from a laboratory scale sequential aerobic sludge blanket (SASB) bioreactor fed with glucose as the main source of carbon and energy. Deoxyribonucleic acid (DNA) was extracted from the young, mature and old granules. The polymerase chain reaction (PCR) was used to amplify the Eubacterial 16S ribosomal DNA (rDNA) and three clone libraries were constructed, corresponding to each of the three growth stages. The microbial diversity in each clone library was assessed by amplified ribosomal DNA restriction analysis (ARDRA). The results reveal that there was considerable diversity in each clone library and there were variations in microbial diversity among the three different clone libraries. This suggests a shift in the composition of the microbial communities. Microorganisms associated with 5 restriction fragment length polymorphism (RFLP) types (A, B, C, D and E) appear to play an important role in the development of aerobic granules.