NON-SPREADING CYTOPHAGAS IN ACTIVATED SLUDGE

Abstract

Spreading and non-spreading colonies of yellow pigmented, flexirubin- positive bacteria were observed regularly on agar plates inoculated with samples from different activated sludge and trickling filter sources. One part of the non-spreading colonies formed spreading colonies after transfer to more suitable growth media. The other part was never observed to form spreading colonies on various growth media tested. However, when examined microscopically in wet mount preparations most of the non-spreading isolates showed the same type of gliding motility as the spreading isolates. In order to test the taxonomic homogeneity as well as possible relationships to "classical" cytophagas, 25 non-spreading isolates were examined for 41 morphological and physiological characteristics. Of the strains tested, 19 had more than 80 % of the characteristics in common. Besides their deviating colony growth, the isolates differed from "classical" cytophagas by their more complex growth requirements and by a less wide spectrum of degradation capacities. It is concluded that the nonspreading isolates represent a distinct cluster within a Cytophaga group comprising all strains with gliding motility, flexirubin pigmentation and a G + C base ratio in the range of 32 - 36 %