Activity, diversity and population size of ammonia-oxidising bacteria in oil-contaminated landfarming soil

Chemolithotrophic ammonia-oxidising bacteria (AOB) present in oil-contaminated landfarming soil were studied over two growing seasons in 1999 and 2000. The number of AOB (4-9 × 105 cells g−1 of dry soil) determined with the quantitative polymerase chain reaction (real-time PCR) and the rate of potential ammonium oxidation (0.05-0.28μgNO2--Ng-1ofdrysoilh-1) indicated the presence of stable AOB populations. Denaturing gradient gel electrophoresis (DGGE) profiling and sequence analysis of PCR-amplified AOB 16S rRNA genes showed dominance of Nitrosospira-like sequences in clusters 2 and 3. The present results from the chronically oil-contaminated landfarming soil support the suggested importance of Nitrosospira-like AOB in terrestrial environments.