Use of silica microspheres having refractive index similar to bacteria for conversion of flow cytometric forward light scatter into biovolume.

This research describes an alternative approach for the rapid conversion of flow cytometric Forward Angle Light Scattering (FALS) into bacterial biovolume. The Rayleigh-Gans theory was considered for explaining the main parameters affecting FALS intensity: sensitivity analysis of the model was carried out, taking into account the parameters characteristic of bacterial cells and characteristics of the flow cytometer. For particles with size in the typical range of bacteria, the FALS intensity is affected mainly by volume and refractive index of bacterial cells and is approximately independent of the shape of the cells.

Effects of sonication on bacteria viability in wastewater treatment plants evaluated by flow cytometry--fecal indicators, wastewater and activated sludge.

The application of sonication to wastewater or sludge contributes to the dispersion of aggregates, the solubilisation of particulate matter with an increase in its biodegradability, the damage of microorganisms due to the loss of cellular membrane integrity. This research is aimed at investigating the effects of sonication at 20kHz frequency on viability of microorganisms present in raw wastewater and activated sludge taken from a municipal wastewater treatment plant, as well as pure strains of Escherichia coli and E. faecalis.

Effects of the metalloid oxyanion tellurite (TeO32-) on growth characteristics of the phototrophic bacterium Rhodobacter capsulatus.

This work examines the effects of potassium tellurite (K2TeO3) on the cell viability of the facultative phototroph Rhodobacter capsulatus. There was a growth mode-dependent response in which cultures anaerobically grown in the light tolerate the presence of up to 250 to 300 microg of tellurite (TeO3(2-)) per ml, while dark-grown aerobic cells were inhibited at tellurite levels as low as 2 microg/ml. The tellurite sensitivity of aerobic cultures was evident only for growth on minimal salt medium, whereas it was not seen during growth on complex medium.

Assessment of activated sludge viability with flow cytometry.

The aim of the study was to evaluate the applicability of fluorescent dyes and multiparameter flow cytometry for the rapid and direct viability/activity assessment of activated sludge samples taken from wastewater treatment plants. Viability and activity of the biomass were estimated respectively through cellular membrane integrity, staining with SYBR Green I and Propidium Iodide, and through fluorogenic dyes capable of detecting enzymatic activity, as FDA and BCECF-AM. A procedure has been developed to disaggregate sludge flocs before dyes staining and cytometric analysis.