IN-SITU IDENTIFICATION OF NOCARDIOFORM ACTINOMYCETES IN ACTIVATED-SLUDGE USING FLUORESCENT RIBOSOMAL-RNA-TARGETED OLIGONUCLEOTIDE PROBES

Hitherto, few environmental samples have been investigated by a 'full cycle rRNA analysis'. Here the results of in situ hybridization experi ments with specific rRNA-targeted oligonucleotide probes developed on the basis of new sequences derived from a previously described compara tive 165 rRNA analysis of nocardioform actinomycetes in activated slud ge are reported. Application of the specific probes enabled identifica tion and discrimination of the distinct populations of nocardioform ac tinomycetes in activated sludge. One of the specific probes (DLP) dete cted rod-shaped bacteria which were found in 13 of the 16 investigated sludge samples from various wastewater treatment plants, suggesting t heir importance in the wastewater treatment process. Another probe (GL P2) hybridized with typically branched filaments of nocardioforms main ly found in samples from enhanced biological phosphorus removal plants , suggesting that these bacteria are involved in sludge foaming. The c ombination of in situ hybridization with fluorescently labelled rRNA-t argeted oligonucleotide probes and confocal laser scanning microscopy improved the detection of nocardioform actinomycetes, which often show ed only weak signals inside the activated-sludge flocs.