Abstract: Eukaryota, bacteria and archaea are the three domains of life. As the third domain of life, archaea has been found not only in extreme environments such as high-temperature, high-saline, and extremely acid habitats, but also in moderate environments including ocean, lake and soil, which implies that archaea may contribute greatly to various ecosystems. By targeting the 16S rRNA gene with real-time PCR approaches, this paper studied the abundance of archaea, crenarchaea and bacteria from two agricultural soil profiles and two long-term fertilization stations Qiyang (QY) and Fengqiu (FQ). The 16S rRNA gene copy number of crenarchaea was 1-2 orders of magnitude lower than that of archaea, and the order of these three groups was crenarchaea < archaea < bacteria. The ratios of both archaea and crenarchaea to bacteria increased with soil depth. The abundance of archaea and  crenarchaea had significantly different responses to different fertilization treatments. In QY station, the copy numbers of archaeal and bacterial 16S rRNA gene had significant positive correlations with soil pH (r=0.850, P<0.01 and r=0.676, P<0.05, respectively); in FQ station, all the 16S rRNA gene copy numbers of archaea, crenarchaea and bacteria had no significant correlations with soil pH, but significantly correlated with soil organic matter (r=0.783, P<0.05;r=0.827,P<0.05;r=0.767, P<0.05, respectively). To understand the distribution of archaea and crenarchaea in agricultural soil could provide important information to evaluate their ecological functions in soil ecosystem and element cycling.

Key words: archaea, crenarchaeota, soil profile, fertilization, real-time PCR