IngentaConnect Comparison between Direct Microscopy and Flow Cytometry for rRNA-...

Authors: Perez-Feito, Rafael; Peccia, Jordan; Noguera, Daniel R

Source: Water Environment Research, Volume 78, Number 2, February 2006 , pp. 181-188(8)

Publisher: Water Environment Federation

Abstract:

A comparison of the quantification of a specific microbial group in activated sludge by fluorescent in-situ hybridization, coupled with either direct microscopic counting or flow cytometry, was performed using an enhanced-biological-phosphorus-removal, sequencing-batch reactor. The population dynamics of Candidatus Accumulibacter phosphatis ( Cand. A. phosphatis) was evaluated during two separate runs of the reactor. With the operational conditions used, Cand. A. phosphatis was enriched until a failure in the pH controller eliminated its ecological advantage. As a result, the comparison of quantification techniques included Cand. A. phosphatis concentrations as low as 11% and as high as 96% of the total cells in the samples. The analysis demonstrated that, regardless of the particular limitations of each technique, both provided similar results when the activated-sludge flocs were easily dispersed. However, when the activated-sludge samples contained flocs that were difficult to disperse, flow cytometry failed to provide quantitative results.

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Comparison between Direct Microscopy and Flow Cytometry for rRNA-Based Quantification of Candidatus Accumulibacter phosphatis in Activated Sludge