PHYLOGENETIC PROBES FOR ANALYZING ABUNDANCE AND SPATIAL-ORGANIZATION OF NITRIFYING BACTERIA

A hierarchical set of five 16S rRNA-targeted oligonucleotide DNA probe s for phylogenetically defined groups of autotrophic ammonia and nitri te-oxidizing bacteria was developed for environmental and determinativ e studies. Hybridization conditions were established for each probe by using temperature dissociation profiles of target and closely related nontarget organisms to document specificity. Environmental applicatio n was demonstrated by quantitative slot blot hybridization and whole-c ell hybridization of nitrifying activated sludge and biofilm samples. Results obtained with both techniques suggested the occurrence of nove l populations of ammonia oxidizers. In situ hybridization experiments revealed that Nitrobacter and Nitrosomonas species occurred in cluster s and frequently were in contact with each other within sludge flocs.