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Presence and activity of ammonia-oxidising bacteria detected amongst the overall bacterial diversity along a physico-chemical gradient of a nitrifying wastewater treatment plant

Lookup NU author(s): Dr Michael Milner, Professor Thomas CurtisORCiD, Professor Russell DavenportORCiD

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Abstract

We wished to discover if we could gain greater insights into how biological treatment plants function by contrasting the presence and activity of the most abundant Bacteria in plug flow and completely mixed activated sludge plants. Presence was assessed by amplifying 16S rRNA gene fragments (using PCR) and activity by amplifying native 16S rRNA, using reverse-transcriptase PCR (RT-PCR), using Bacteria-specific primers. The amplified sequences were compared using denaturing gradient gel electrophoresis (DGGE). The plug flow plant exhibited a strong physico-chemical gradient with an initial anoxic zone, whilst the two completely mixed reactors did not. Similarities were observed between the profile of the banding pattern for presence and activity. However, in the plug flow reactor one prominent band was detected in the active population (16S rRNA) but was absent from the corresponding profile of the 16S rRNA gene. Sequencing of this band revealed its identity as a Nitrosomonas-like sequence. The intensity of the 16S rRNA sequenced varied along the physico-chemical gradient of the plug-flow reactor in a manner that coincided with the growth of ammonia-oxidising bacteria (AOB) and the loss of ammonia. This band was also absent from the completely mixed reactors, although significant numbers of AOB were detected in all systems (∼106-108 cells ml-1) by fluorescence in situ hybridisation (FISH). An abundant and highly active AOB population was present in the anoxic zone of the plug-flow reactor where up to 60% of the total ammonia was removed. An examination of nitrogen removal/production rates, together with the above data, reveal that complex nitrogen removal processes occur in this system. These data also enabled the calculation of a specific in situ growth rate for the AOB as 0.12 h-1. © 2008 Elsevier Ltd. All rights reserved.

Publication metadata

Author(s): Milner MG, Curtis TP, Davenport RJ

Publication type: Article

Publication status: Published

Journal: Water Research

Year: 2008

Volume: 42

Issue: 12

Pages: 2863-2872

ISSN (print): 0043-1354

ISSN (electronic): 1879-2448

Publisher: Pergamon

URL: http://dx.doi.org/10.1016/j.watres.2008.02.019

DOI: 10.1016/j.watres.2008.02.019

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