Download poster «Identification and abundance of Thiothrix in WWTPs treating domestic wastewater using FISH»
Bacteria that belong to the genus Thiothrix are characterized by distinctive morphological features, such as filamentous growth and accumulation of sulphur granule when incubated in the presence of sulphide or thiosulphate.
The Thiothrix morphotypes occur in municipal and industrial WWTPs with and without nutrient removal. Traditionally, the problems of biological bulking have been monitored by classical microscopy such as morphological observation and polychromatic staining. Few works have been carried out for the detection of Thiothrix in WWTP samples with molecular procedures such as the fluorescence in situ hybridization (FISH) technique. In this study, we investigated several Spanish WWTPs with the FISH technique to analyze the composition of Thiothix species and their relathionships with physico-chemical and operational parameters. Samples of activated sludge were collected from four Spanish WWTPs and analyzed by light microscopy and quantitative FISH. In the FISH analysis a set of 10 rRNA-targeted nucleic acid FISH probes covering Thiothrix genus and species were used. The abundance of filamentous bacteria in the 139 activated sludge samples was measured according to the subjective scoring method of Eikelboom (2000) where observations are rated on scale from 0 (none) to 5 (extensive growth). Thiothrix filaments were present in the four WWTP analyzed. In 92 (66,2 %) of the samples, Thiothrix filaments were observed with the probe G123T. It was evident that mixed populations of Thiothrix spp. were present in the activated sludge samples investigated, the observed differences were in the relative abundance of the various groups. These findings were supported by the results obtained using conventional microscopy. T. eikelbomii, T. nivea and T. fructosivorans were common (FI>3) in two of the four WWTP analyzed. No fluorescence signal was detected with the probes G1B (T. disciformis), G3M (T. flexilis) and Meg1028+Meg 983 (Meganema perideroedes). Redundancy analysis (RDA) ordination diagram (biplot) suggested different behaviour among species within genus Thiothrix. T. eikelbomii showed a positive relationship with the reactor temperature (Tr). Conversely, T. fructosivorans was negatively related with Tr. T. nivea and T. fructosivorans were associated with high sludge retention time (SRT) values and low values of organic loading rate (OLR). T. nivea showed a positive relationship with the hydraulic retention time (HRT) and negative with the influent carbohydrates and proteins. T. eikelbomii and T. nivea were associated with nitrogen and phosphorus deficit (BOD5/TN/TP).
Romero, V., Zornoza, A., Alonso, J.L. (2012) V International Conference on Environmental, Industrial and Applied Microbiology – BiomicroWorld 2013. Madrid, Spain.