Substrate uptake by Gordonia amarae in activated sludge foams by FISH-MAR.

Gordonia amarae is a right-angled branching filament belonging to the mycolic acid-containing Actinobacteria which is commonly found in many foaming activated sludge wastewater treatment plants. Although studies on different substrates as sole carbon sources by pure cultures of G. amarae have been carried out, none have examined substrate uptake by this organism in situ. Uptake of several hydrophilic and hydrophobic substrates by G. amarae was evaluated in situ using a combination of fluorescence in situ hybridization and microautoradiography. G. amarae could assimilate a range of both hydrophilic and hydrophobic substrates. From the data, G. amarae appears to be physiologically active under aerobic, anaerobic and anoxic condition (NO2 and NO3) for some substrates. This might explain why attempts to control foaming caused by G. amarae using anoxic and anaerobic selectors have been unsuccessful. This study emphasizes that bacteria can behave differently in situ to pure cultures and that it is important to evaluate the in situ physiology of these bacteria if we are to better understand their role in the wastewater treatment process.

The in situ physiology of "Nostocoida limicola" II, a filamentous bacterial morphotype in bulking activated sludge, using fluorescence in situ hybridization and microautoradiography.

The in situ physiology of the actinobacterial bulking and foaming filamentous bacterium "Nostocoida limicola" II was studied by fluorescence in situ hybridization/microautoradiography. Substrate assimilation patterns of pure cultures of this bacterium were different to those seen in activated sludge biomass samples. There was no evidence to suggest that "N. limicola" II preferred hydrophobic substrates, but evidence was produced to support the view that it is metabolically active under anaerobic conditions in activated sludge.

Effects of culture conditions on the mycolic acid composition of isolates of Rhodococcus spp. from activated sludgefoams.

The influence of two different carbon sources and three incubation temperatures on the mycolic acid compositions of three Rhodococcus isolates from activated sludge was examined using Selective Ion Monitoring (SIM) gas chromatography-mass spectrometry (GC-MS). Considerable qualitative and quantitative differences were detected in the mycolic acid compositions of the three very closely related isolates grown under the same conditions. Culture age also affected both the chain lengths and proportions of saturated mycolic acids detected in cell extracts, but not in the same manner for each isolate. Mycolic acids generally were of shorter chain lengths in cells grown with Tween 80 compared to glucose grown cells in strain 11R but the opposite situation occurred with strains A7 and D5. In all three, the proportion of unsaturated mycolic acids decreased with increasing growth temperatures. The taxonomic relevance of these observations and possible explanations for the observed changes in mycolic acid composition under various culture conditions are discussed.