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| Titel |
Does the source of carbon influence the abundance of nirK, nirS and nosZ functional genes in laboratory denitrification bioreactors? |
| VerfasserIn |
Maria Barrett, Owen Fenton, Tristan G Ibrahim, Vincent O'Flaherty, Mark G. Healey |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250093259
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| Publikation (Nr.) |
 EGU/EGU2014-7836.pdf |
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| Zusammenfassung |
| Biological denitrification in soil is the main producer of nitrous oxide (N2O) emissions.
Denitrifying soil microbes are capable of reducing nitrate (NO3-) to nitrite (NO2-) to N2O
and di-nitrogen gas (N2). One third of these denitrifers possess a truncated functional gene
pathway, which may lack the nosZ gene and emit N2O as a final emission product instead of
the more benign N2. A carbon rich environment, specific to certain types of carbon sources,
has been shown to foster an anaerobic environment, which positively impacts microbial
denitrification rates. The present study examined the effect of varying carbon sources in
laboratory-scale denitrification bioreactors on NO3- removal and also correlated
performance with the abundance of the denitrifying microbial consortia possessing the
denitrifying functional genes nirK, nirS and nosZ in each bioreactor. The bioreactors
comprised either lodgepole pine woodchips (LPW), lodgepole pine needles (LPN),
barley straw (BBS), or cardboard (CCB), each mixed with soil in a 1:1 ratio (by
volume) and subject to sequentially increasing hydraulic loading rates of 3, 5 and
10 cm d-1 for a total operation period of up to 744 days. A reactor containing
soil only (CSO) was used as the study control. The abundance of denitrifers was
determined by targeting nirK, nirS, nosZ functional genes and the overall microbial
population was determined by targeting bacterial and archaeal 16sRNA genes.
Nitrate removal from all bioreactors was > 99.7%, but when pollution swapping was
considered, this ranged from 67% for LPW to 95% for the CCB ; this was also mirrored
in the average nirk/nirS/nosZ gene abundance (CCB, c. 94% (c. 108); LPN, 75%
(c. 107); BBS, c. 74% (c. 106/107); LPW, 70% (c. 105). Bacterial 16sRNA gene
abundance was similar in all reactors including the control (P=0.0362). The abundance
of nosZ genes and the genetic potential for N2 emissions varied in all reactors in
comparison to the control CSO, BBS (P=0.0051); CCB (P=0.0171); LPN (P= 0.0049)
and LPW (P= 0.0008). Interestingly, nirS gene abundance was on average much
higher than that of nirK and nosZ in the LPN and LPW reactors compared to the
CSO, BBS and CCB reactors, indicating a habitat/carbon source preference for
denitrifying organisms. Indeed, the high abundance of nir genes in comparison to the total
bacterial abundance indicates the possible denitrifying role of fungal and archaeal
organisms, which warrants further investigation. The addition of carbon had a direct
impact on denitrifer abundance (CSO-104/105; CCB/BBS/LPN/LPW- 107/108). |
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