ACTIVATED-SLUDGE FOAMING - THE TRUE EXTENT OF ACTINOMYCETE DIVERSITY

Isolates from activated sludge foam were provisionally assigned to the genera Gordona and Tsukamurella on the basis of colony morphology and pigmentation. Representatives of the first group were compared with m arker strains of validly described species of Gordona by using Curie-p oint pyrolysis mass spectrometry. Most of the isolates fell into a num ber of taxa which were equated with groups of marker strains which cor responded to the known Gordona species. In a corresponding experiment the activated sludge isolates, which were provisionally labelled ''Tsu kamurella spumae'' formed a group which was well separated from the ma rker strains of the genus. Representatives of the isolates were found to have chemical properties consistent with their classification in th e genus Tsukamurella. 16S rDNA sequence data, when taken with previous DNA:DNA relatedness results, suggest that Tsukamurella paurometabola is heterogeneous. Similarly, the sequence data provide some evidence t hat ''Tsukamurella spumae'' may merit recognition as a novel species. (C) 1998 IAWQ. Published by Elsevier Science Ltd.