IDENTIFICATION AND IN-SITU DETECTION OF GRAM-NEGATIVE FILAMENTOUS BACTERIA IN ACTIVATED-SLUDGE

Gram-negative filamentous bacteria are commonly observed in activated sludge and contribute to poor settlement of activated sludge flocs in secondary sedimentation tanks, a problem referred to as activated slud ge bulking. However, the standard morphological identification system is of limited value for a high resolution, rapid monitoring of these b acteria. Therefore, specific 16S rRNA-targeted oligonucleotide probes were developed for Haliscomenobacter spp., Sphaerotilus spp., Leptothh ix spp., Thiothrix spp., Leucothrix mucor and bacteria of the Eikelboo m type 021N. Probe specificities were evaluated by nonisotopic dot blo t hybridization to 145 reference strains representing a diverse collec tion of taxa. In situ hybridization with fluorescent probe derivatives was combined with scanning confocal laser microscopy (SCLM) for analy zing the three dimensional localization of the filaments inside the sl udge flocs. Filaments could be localized even in the center of fixed f locs at a high resolution undisturbed by problems like autofluorescenc e.