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A flow cytometry method for bacterial quantification and biomass estimates in activated sludge

Lookup NU author(s): Dr Mathew Brown, Catherine Hands, Tamara Coello Garcia, Badruddeen Sani, Dr Amelie Ott, Sarah Smith, Professor Russell DavenportORCiD



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


© 2019 The Authors Absolute bacterial quantification receives little serious attention in the literature compared to sequencing, conceivably because it is considered unimportant and facile, or because existing methods are tedious, laborious and/or biased in nature. This is particularly true in engineered systems, including activated sludge, where such information underpins their design and operation. To overcome these limitations we built upon existing work and optimised and comprehensively validated, through comparison with epifluorescence microscopy (EFM), a rapid and precise flow cytometric protocol to enumerate total bacterial numbers in activated sludge. Insights into potential biases were evaluated using appropriate statistical analyses on this comparison, which spanned four orders of magnitude, as well as comparing volatile suspended solid (VSS) concentrations. The results suggest flow cytometry (FCM) is a rapid, reproducible and economical technique for quantifying total bacterial numbers and biomass concentrations in activated sludge, despite within order of magnitude discrepancies with EFM counts, which had inherent and evidently greater errors and biases than FCM. The use of FCM for routine monitoring over both EFM and VSS should help further understanding of the microbial ecology in, and the operation of, engineered systems.

Publication metadata

Author(s): Brown MR, Hands CL, Coello-Garcia T, Sani BS, Ott AIG, Smith SJ, Davenport RJ

Publication type: Article

Publication status: Published

Journal: Journal of Microbiological Methods

Year: 2019

Volume: 160

Pages: 73-83

Online publication date: 26/03/2019

Acceptance date: 25/03/2019

Date deposited: 08/04/2019

ISSN (print): 0167-7012

ISSN (electronic): 1872-8359

Publisher: Elsevier B.V.


DOI: 10.1016/j.mimet.2019.03.022


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