ULTRASTRUCTURE OF MICROTHRIX-PARVICELLA FROM ACTIVATED-SLUDGE

Filaments of Microthrix pasvicella grow Very poorly in pure culture an d have a characteristic uneven appearance containing large numbers of distinctive spherical swollen cells. This feature was only rarely seen with filaments of this organism in activated sludge biomass samples. Ultrastructurally, these spherical swollen cells do not appear to be b acterial endospores or cysts, but do show features that are consistent with them being some form of resting structure. Their production coul d be a response of M. parvicella to environmental stress, an explanati on proposed because of their relative predominance in pure cultures of M. parvicella compared to their infrequent occurrence in filaments of this bacterium observed in activated sludge biomass.