Analysis at the genomospecies level of microbial populations changes in activated sludge: the case of Aeromonas

To study how microbial populations in activated sludge change over time, an analysis of Aeromonas populations from a municipal activated sludge plant was carried out at two different periods: the first was characterized by low influent biochemical oxygen demand (BOD), chemical oxygen demand (COD), NH+4 and PO3−4, and the other by high values. Aeromonas strains were isolated on 10 μg/l of C-glucose in starch glutamate ampicillin penicillin (SGAP-10C) medium and classified into 12 DNA hybridization groups (DHG), using biochemical tests and numerical identification. Strains not differentiated by this method were ribotyped. Results revealed a difference in composition of Aeromonas DHGs: in the period characterized by high values of the parameters measured, the activated sludge displayed a wide diversity, whereas the period with low values showed reduced diversity and a modification of the dominant DHGs.