16S RIBOSOMAL-RNA ANALYSIS OF ISOLATES OBTAINED FROM GRAM-NEGATIVE, FILAMENTOUS BACTERIA MICROMANIPULATED FROM ACTIVATED-SLUDGE

Individual filaments of the Gram negative, bulking filamentous morphot ypes Eikelboom Type 0092, Type 0411, TT;pe 0803 and Herpetosiphon sp. were identified in activated sludge mixed liquors and specifically iso lated by micromanipulation. Although their isolation and partial pheno typic description have previously been reported, we sought them to det ermine their phylogenetic position and to compare our data with the pr evious descriptions. Direct cell lysis procedures and the polymerase c hain reaction were used to obtain their 16S rRNA genes, These were seq uenced and the data were analysed to phylogenetically place the filame nts into their respective lines of descent in the domain Bacteria. Typ e 0803 is a member of the Rubrivivax subgroup of the beta proteobacter ial subclass; Herpetosiphon sp. belongs in the Chloroflexus subdivisio n of the green non-sulfur lineage and its sequence is most similar to that of H. aurantiacus; while Type 0092 and Type 0411 belong in the Fl exibacter-Cytophaga-Bacteroides phylum. The contemporary ''identificat ion'' of these organisms is ambiguous and relies on subjective morphol ogical criteria and staining reactions. However, the sequence data rep orted here are being examined for morphotype-specific regions to be ex ploited for RNA-directed, DNA probes for rapid, unequivocal, in situ i dentification of each filament type.