Growth of an activated sludge foam-forming bacterium, Nocardia pinensis, on hydrophobic substrates

Nocardia pinensis is a very slow-growing organism in pure culture, yet grows well enough to cause serious foaming problems in activated sludge plants. On hydrophobic substrates like olive oil and Tween 80, it produced more biomass, and grew much faster, than on a simple hydrophilic substrate like glucose. On olive oil it also grew as compact clumps of branching filaments which attached to the oil droplets, suggesting a possible mechanism for competing with other less hydrophobic, but faster growing, organisms. These results are discussed in relation to ecological strategies of the organism in activated sludge plants.