Influence of temperature on the composition and activity of denitrifying soil communities.

The impacts of temperature on the activity and on the size as well as on the community composition of denitrifiers in an agricultural soil were studied in a controlled laboratory experiment. Soil slurries were incubated at different temperatures (4, 15, 20, 25, and 37 degrees C) under nonlimiting substrate conditions for 3 weeks. The abundance of the nitrate-reducer community in general was determined using the most probable number (MPN) technique; denitrifier activity and community composition were assessed by measuring potential denitrifier enzyme activity and by terminal restriction fragment length polymorphisms as well as by phylogenetic analysis of nitrite reductase gene amplicons (nirK and nirS). Increasing incubation temperatures resulted in gradually enhanced denitrification activity, but also in higher abundance of nitrate reducers and in different denitrifier community compositions. Genetic and physiological characterization of isolates purified from the highest dilution of the MPN series emphasized community differences. Overall, temperature apparently not only affected process rates but also resulted in the enrichment of denitrifiers and shifts in the community composition.