CANDIDATUS-MICROTHRIX-PARVICELLA, A FILAMENTOUS BACTERIUM FROM ACTIVATED-SLUDGE SEWAGE-TREATMENT PLANTS

''Candidatus Microthrix parvicella'' is a filamentous bacterium that g rows with great difficulty in cultures from the mixed liquor of activa ted sludge sewage treatment plants. It is gram positive, and the ultra structure of its cell walls has been determined to be of the gram-posi tive type by electron microscopical examination. Phylogenetically, it is a deep-branching member of the subphylum actinomycetes within the g ram-positive phylum of the domain Bacterin. As for phenotypic features , it is known that the organism contains polyphosphate inclusions and that it is catalase positive. In mixed cultures in activated sludge pl ants and in pure culture in the laboratory, it has a characteristic an d distinctive winding filamentous morphology, with filaments hundreds of micrometers long.