The maximum ammonia oxidation potential (AOP) of a topsoil in Langhovde, East Antarctica was 22.1 +/- 2.4 ng N g(-1) dry soil h(-1) (2 mM ammonium, 10 degrees C, n=3). This topsoil exhibited twin AOP peaks (1 and 2 mM ammonium) at 10 degrees C, but not at 20 degrees C. Six and ten operational taxonomic units (OTUs) were identified for ammonia-oxidizing bacteria (AOB) and archaea (AOA) amoA, respectively. AOB were classified into Nitrosospira: the two dominant OTUs corresponded to the Mount Everest cluster. AOA were classified into time clusters; Nitrososphaera and Nitrosocosmicus were the two dominant clusters.