Abundance and spatial organization of Gram-negative sulfate-reducing bacteria in activated sludge investigated by in situ probing with specific 16S rRNA targeted oligonucleotides

摘要

A comprehensive panel of ten 16S rRNA targeted oligonucleotides specific for mesophilic sulfate-reducing bacteria (SRB) within the delta-subclass of Proteobacteria was developed as a diagnostic tool and evaluated for its specificity and in situ applicability. Five probes (DSD131, DSBO224, DSV407, DSR651, DSS658) are specific on genus level and five probes identify distinct phylogenetic subbranches within the families Desulfobacteriaceae (DSMA488, DSB985) and Desulfovibrionaceae (DSV214, DSV698, DSV1292). All oligonucleotides were checked for their specificity by computer aided comparative sequence analysis, For in situ application optimal stringency conditions were adjusted for each fluorescence-labelled probe performing whole cell hybridizations using target and non-target organisms. Activated sludge flocs from different stages within the aeration rank of a large municipal wastewater treatment plant were examined by in situ hybridizations with the indocarbocyanine-(Cy3-) labelled SRB-specific probes. The relative abundance and the spatial organization of single SRB were monitored with epifluorescence and confocal laser scanning microscopy. Individual sulfate-reducing cells could be visualized and the number of cells ranged from 0.5 to 8% of the total cell counts within all stages of the activated sludge process and the final clarifier. Cells yielding strong fluorescence signals after hybridization with the newly developed probes were not restricted to anoxic and anaerobic compartments, but were also clearly detectable in the aeration zones of the treatment plant. (C) 1998 Federation of European Microbiological Societies. Published by Elsevier Science B.V. [References: 64]