Purpose of study Biological foaming is one of the major separation problems encountered in biological wastewater treatment plants (WWTPs). Mycolata are branched taxa, such as Gordonia, Nocardia, Skermania and Rhodococcus, which are known to form foam in activated sludge wastewater treatment plants preventing the solid separation and reducing the effluent quality. This foam can block the scum removal systems and may contain up to 40% of the total solids plants. Many filamentous bacteria can now be detected in activated sludge or foam using 16S or 23S rRNA gene-targeted oligonucleotide probes designed for Fluorescence in situ hybridisation (FISH). There is considerable interest in identifying the filamentous bacteria in WWTPs and characterizing their in situ physiologic properties, in order to develop specific control strategies to suppress their growth. The objectives of our study were to monitor the mycolata in a number of WWTPs, in an attempt to identify them by FISH and to study their phosphatase and glucuronidase exo-enzyme activities using ELF substrates. Methods Activated sludge and scum samples were taken from the aeration tanks of two municipal WWTPs with scum problems. The plants were repeatedly sampled over a period of seven months. FISH was performed on fixed activated sludge as specified by Schade and Lemmer . The oligonucleotide probes used for FISH in this study were, Myc657 (mycolata) and Gor0596 (Gordonia genus). The presence of exo-enzyme activity was determined using ELF (ELF-97ïŸ…, Molecular Probes; www.probes.invitrogen.com), as described by Schade and Lemmer . The following enzymes were evaluated: ELF-97ïŸ… Î²-D-glucuronidase (ELF-97ïŸ… Î²-D-glucuronide) and ELF-97ïŸ… phosphatase (ELF-97ïŸ… endogenous phosphatase detection kit). If any exo-enzymatic activity was expressed, the nonfluorescent substrate was cleaved, and fluorescent crystals (yellow) precipitated directly on the bacterial surface; these were visible by epifluorescence microscopy. Results and Conclusions Mycolata were shown to yield positive results with group-specific probe Myc657 detecting mycolic acid-containing actinomycetes. Besides the filamentous morphotype, Gordonia amarae-like organisms (GALO) were found in the samples investigated of the two WWTPs with the Gor0596 probe. Activity assignment proved numerous GALO to show clear activites for phosphatase and glucuronidase as described by Schade and Lemmer . The in situ activities of mycolata involved in scum problems are shown in Figure 1. In situ activities in scum were equal, compared to activated sludge for the mycolata investigated. However, because of their higher bacteria numbers in scum their activity increases in the floated sludge fraction as compared to activated sludge. Kragelund et al.  investigated the viability of mycolata, and suggested that their survival is presumably due to storage reserves (PHA) and consumption of extracellular material facilitated by expression of exo-enzymes.
|Publication status||Published - 2009|
|Event||15th International Symposium on the Biology of Actinomycetes, Shanghai International Convention Centre - Shanghai, China|
Duration: 1 Jan 2009 → …
|Conference||15th International Symposium on the Biology of Actinomycetes, Shanghai International Convention Centre|
|Period||1/01/09 → …|