COMPARISON OF PARTIAL 16S RIBOSOMAL-RNA GENE-SEQUENCES OBTAINED FROM ACTIVATED-SLUDGE BACTERIA

The cultivated and uncultivated bacterial communities of an activated sludge plant were studied. Two samples were taken and a total of 516 b acterial isolates were classified into groups using their whole-cell p rotein patterns. The distribution of bacteria into protein-pattern gro ups differed significantly between tl-le two samples, suggesting varia tion in culturable bacterial flora. Partial 16S rRNA gene sequences we re determined for representatives of the commonest protein-pattern gro ups. Most of the sequences obtained were previously unknown, but relat ively closely related to known sequences of organisms belonging to the alpha, beta or gamma subclasses of the proteobacteria, the first two subclasses being predominant. This classification of bacteria isolated on a diluted nutrient-rich medium differed from recent culture-depend ent studies using nutrient-rich media. The uncultivated bacterial comm unity was studied by analyzing ten partial 16S rRNA gene sequences clo ned directly from activated sludge. None of the cloned sequences was i dentical to those determined for culturable organisms; or to those in the GenBank database. They were, however, related to the alpha or beta subclasses of the proteobacteria, or to the gram-positive bacteria wi th a high G + C DNA content.