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Effect of pH, temperature and substrate on N₂O, NO and CO₂ production by Alcaligenes faecalis p

Kesik, M., Blagodatsky, S., Papen, H., Butterbach-Bahl, K.
Journal of applied microbiology 2006 v.101 no.3 pp. 655-667
Alcaligenes faecalis, Paracoccus pantotrophus, carbon dioxide, citrates, environmental factors, gases, microorganisms, models, nitric oxide, nitrous oxide, pH, soil, temperature
To study the effect of pH, temperature and substrate on the magnitude of N₂O and NO production by heterotrophic nitrifiers. The change in N₂O and NO production by the heterotrophic nitrifiers Alcaligenes faecalis subsp. parafaecalis and Paracoccus pantotrophus because of variations in pH, temperature and substrate was studied in chemostat cultures under steady-state conditions. N₂O, NO and CO₂ production increased with temperature between 4 and 32°C. For N₂O an optimum temperature of 28°C was observed. No optimum temperature was found for NO. Highest N₂O and CO₂ productions were observed at a pH of 7·0. However, besides having an optimum at pH 7·0, especially NO production but also N₂O production increased significantly at pH <= 4·0. This increase in NO production under acidic conditions was partly because of chemo-denitrification, which contributed up to 62% of total NO production at pH 3·0 (0·8% for N₂O). Furthermore, we could demonstrate that substrate quality significantly affects N₂O, NO and CO₂ production. N₂O and especially NO production by A. faecalis p. was significantly lower on an ammonium citrate medium when compared with rates obtained for a peptone-meat extract medium. The results indicate that heterotrophic nitrifiers are suitable model organisms to study the influence of environmental factors on microbial N trace gas production. The results allow an improved description, e.g. of the pH dependency of N trace gas production by microbes and/or chemo-denitrification in process-oriented models describing the exchange of N trace gases between soils and the atmosphere.