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Agreement between theory and measurement in quantification of ammonia-oxidizing bacteria

Lookup NU author(s): Gulnur Coskuner, Stuart Ballinger, Professor Russell DavenportORCiD, Rheanne Pickering, Dr Rosario Solera Del Rio, Professor Ian Head, Professor Thomas CurtisORCiD


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Autotrophic ammonia-oxidizing bacteria (AOB) are of vital importance to wastewater treatment plants (WWTP), as well as being an intriguing group of microorganisms in their own right. To date, corroboration of quantitative measurements of AOB by fluorescence in situ hybridization (FISH) has relied on assessment of the ammonia oxidation rate per cell, relative to published values for cultured AOB. Validation of cell counts on the basis of substrate transformation rates is problematic, however, because published cell-specific ammonia oxidation rates vary by over two orders of magnitude. We present a method that uses FISH in conjunction with confocal scanning laser microscopy to quantify AOB in WWTP, where AOB are typically observed as microcolonies. The method is comparatively simple, requiring neither detailed cell counts or image analysis, and yet it can give estimates of either cell numbers or biomass. Microcolony volume and diameter were found to have a log-normal distribution. We were able to show that virtually all (> 96%) of the AOB biomass occurred as microcolonies. Counts of microcolony abundance and measurement of their diameter coupled with a calibration of microcolony dimensions against cell numbers or AOB biomass were used to determine AOB cell numbers and biomass in WWTP. Cell-specific ammonia oxidation rates varied between plants by over three orders of magnitude, suggesting that cell-specific ammonia oxidation is an important process variable. Moreover, when measured AOB biomass was compared with process-based estimates of AOB biomass, the two values were in agreement.

Publication metadata

Author(s): Coskuner G, Ballinger SJ, Davenport RJ, Pickering RL, Solera R, Head IM, Curtis TP

Publication type: Article

Publication status: Published

Journal: Applied and Environmental Microbiology

Year: 2005

Volume: 71

Issue: 10

Pages: 6325-6334

ISSN (print): 0099-2240

ISSN (electronic): 1098-5336

Publisher: American Society for Microbiology


DOI: 10.1128/AEM.71.10.6325-6334.2005


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