NUMERICAL TAXONOMY OF SKERMANIA-PINIFORMIS AND RELATED ISOLATES FROM ACTIVATED-SLUDGE

The microscopic morphology of nocardioforms causing foaming problems i n activated sludge usually consists of filaments with branches at eith er right angles (Nocardia amarae-Like Organisms, NALO) or acute angles (Pine Tree-Like Organisms, PTLO). Fifty-nine nocardioforms, mainly wi th PTLO morphology, isolated from mixed liquor and foam samples from A ustralian activated sludge plants, and 39 reference strains of nocardi oforms, including type strains, were characterized using 109 morpholog ical and physiological characters. Cluster Analysis and Principal Comp onent Analysis showed that the activated sludge isolates clustered in six groups. All isolates that had typical PTLO morphology clustered un ambiguously with the Skermania piniformis type strain (formerly called Nocardia pinensis) showing that, unlike NALO, reliable unequivocal id entification of S. piniformis, based on microscopic morphology in acti vated sludge, was possible. Other foam isolates whose morphology consi sted of branches with both acute angles and right angles clustered as two separate groups, probably representing new species. These could no t be confused microscopically with S. piniformis, despite some branche s showing acute angles. The remaining three groups had typical NALO mo rphology. One of these groups did not cluster with any reference cultu res and may be a new species or genus.