The in situ physiology of pine tree like organisms (PTLO) in activated sludge foams

Abstract

The in situ physiology of filamentous bacteria with acute angle branching, or Pine tree like organisms (PTLO), from activated sludge foams was investigated with a focus on its response to hydrophobic substrates. Microautoradiographic studies revealed that PTLO are very selective in their substrate utilization in foams, only taking up oleic acid among many substrates tested, but carrying this out under aerobic, anaerobic, and anoxic conditions. Data from applying a combination of in situ techniques indicated that a high proportion of the PTLO were metabolically inactive in the foam. Most showed only low respiratory activity as detected with the redox dye CTC and low intensity signals from FISH probing with 16S rRNA targeted probes. A strong correlation was noticed between their accumulation of storage material in the form of polyhydroxyalkanoates and their intensity of fluorescent FISH signals. In situ surface properties of these PTLO as visualized by the adhesion of fluorescent hydrophobic spheres to individual filaments suggest that their relative hydrophobicities reflected their in situ cell viability. Active ectoenzyme activity was detected in many filaments but this activity did not correspond to the substrate uptake data.