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:: Reference
1: FEMS Microbiol Ecol. 2008 Oct;66(1):167-80. Epub 2008 Jun 8.
Functional robustness and gene pools of a wastewater nitrification reactor:
comparison of dispersed and intact biofilms when stressed by low oxygen and low
pH.
Mao Y, Bakken LR, Zhao L, Frostegard A.
Department of Chemistry, Biotechnology and Food Science, Norwegian University of
Life Sciences, Aas, Norway. stone-raining@sjtu.edu.cn
The functional robustness of biofilms in a wastewater nitrification reactor, and
the gene pools therein, were investigated. Nitrosomonas and Nitrosospira spp.
were present in similar amounts (cloning-sequencing of ammonia-oxidizing
bacteria 16S rRNA gene), and their estimated abundance (1.1 x 10(9) cells g(-1)
carrier material, based on amoA gene real-time PCR) was sufficient to explain
the observed nitrification rates. The biofilm also had a diverse community of
heterotrophic denitrifying bacteria (cloning-sequencing of nirK). Anammox 16S
rRNA genes were detected, but not archaeal amoA. Dispersed biofilms (DB) and
intact biofilms (IB) were incubated in gas-tight reactors at different pH levels
(4.5 and 5.5 vs. 6.5) while monitoring O(2) depletion and concentrations of NO,
N(2)O and N(2) in the headspace. Nitrification was severely reduced by
suboptimal O(2) concentrations (10-100 microM) and low pH (IB was more acid
tolerant than DB), but the N(2)O/NO(3)(-) product ratio of nitrification
remained low (<10(-3)). The NO(2)(-) concentrations during nitrification were
generally 10 times higher in DB than in IB. Transient NO and N(2)O accumulation
at the onset of denitrification was 10-10(3) times higher in DB than in IB
(depending on the pH). The contrasting performance of DB and IB suggests that
the biofilm structure, with anoxic/micro-oxic zones, helps to stabilize
functions during anoxic spells and low pH.
Publication Types:
Comparative Study
PMID: 18616585 [PubMed - indexed for MEDLINE]
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