M Kesik1, S Blagodatsky, H Papen, K Butterbach-Bahl. 1. Karlsruhe Research Centre, Institute for Meteorology and Climate Research, Atmospheric Environmental Research, IMK-IFU, Garmisch-Partenkirchen, Germany.
Abstract
AIMS: To study the effect of pH, temperature and substrate on the magnitude of N(2)O and NO production by heterotrophic nitrifiers. METHODS AND RESULTS: The change in N(2)O 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. N(2)O, NO and CO(2) production increased with temperature between 4 and 32 degrees C. For N(2)O an optimum temperature of 28 degrees C was observed. No optimum temperature was found for NO. Highest N(2)O and CO(2) productions were observed at a pH of 7.0. However, besides having an optimum at pH 7.0, especially NO production but also N(2)O production increased significantly at pH <or= 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 N(2)O). Furthermore, we could demonstrate that substrate quality significantly affects N(2)O, NO and CO(2) production. N(2)O 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. CONCLUSIONS: The results indicate that heterotrophic nitrifiers are suitable model organisms to study the influence of environmental factors on microbial N trace gas production. SIGNIFICANCE IMPACT OF THE STUDY: 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.
AIMS: To study the effect of pH, temperature and substrate on the magnitude of N(2)O and NO production by heterotrophic nitrifiers. METHODS AND RESULTS: The change in N(2)O 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. N(2)O, NO and CO(2) production increased with temperature between 4 and 32 degrees C. For N(2)O an optimum temperature of 28 degrees C was observed. No optimum temperature was found for NO. Highest N(2)O and CO(2) productions were observed at a pH of 7.0. However, besides having an optimum at pH 7.0, especially NO production but also N(2)O production increased significantly at pH <or= 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 N(2)O). Furthermore, we could demonstrate that substrate quality significantly affects N(2)O, NO and CO(2) production. N(2)O 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. CONCLUSIONS: The results indicate that heterotrophic nitrifiers are suitable model organisms to study the influence of environmental factors on microbial N trace gas production. SIGNIFICANCE IMPACT OF THE STUDY: 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.