MICROBIOLOGICAL DIVERSITY OF THE BIOFILM GROWTH IN WASTEWATER TREATMENT PONDS

The study aimed to find out the diversity of microbes and the communities changing in the multispecies anaerobic biofilm developed on glass slides of a laboratory scale wastewater treatment pond. The microbial ecology methods, such as polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE), scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) combined with fluorescence in situ hybridization (FISH) were applied to analyze microbial community. The biofilm development could be roughly divided into three stages: an initial attachment phase characterized by random adhesion of the cells to the surface; a consolidation phase defined by the appearance of microcolonies; and maturation phase. During the consolidation period, proteobacteria with broad metabolic capabilities, mainly represented by members of alpha-Proteobacteria class (Oleomonas, Azospirillum), predominated. Archaea first appeared during the consolidation period. A Methanospirillum-like methanogen was detected after 36 h, and this was followed by the detection of Methanosarcina, after 4 days of biofilm development. The mature biofilm displayed a hill and valley topography with cells embedded in a matrix of exopolymer where the spatial distribution of the microorganisms became well-established. Compared to the earlier phases, the biodiversity had greatly increased. Within the domain Archaea, the acetoclastic methanogen Methanosaeta concilii become dominant. This study provides insights on the trophic web and the shifts in population during biofilm development in a laboratory scale wastewater treatment pond.