S9). It is further confirmed by the coverage estimators of Chao1, which showed a high value of the hzsB clone library than that of the 16S rRNA gene (16.9 vs. 5). The Shannon (2.2 vs. 1.35) and Simpson (0.14 vs. 0.27) indices also implied a higher buy AZD6244 diversity of

anammox bacteria by amplifying the hzsB gene. Compared with primers targeting the hzsA subunits, similarly high specificities were observed that no false positives were detected in 92 (hzsB) and 46 (hzsA) clones. The primer pair of hzsB_396F and hzsB_742R was applied for the quantification of anammox bacterial abundance in the soil core. The copy number measured in the surface sample (0–10 cm) was 7.0 ± 0.3 × 105 copies g−1 dry soil and decreased slightly to 2.0 ± 0.9 × 105 copies g−1 dry soil at 20–30 cm depth as shown in Fig. 2a. Below this depth, hzsB gene copy numbers increased and peaked at 40–50 cm depth of 2.7 ± 1.3 × 106 copies g−1 dry soil,

which accounts for about 2.3% of total bacterial cells (Fig. 2c) assuming that the anammox bacteria contained one copy of the hzsCBA gene cluster (Strous et al., 2006; Kartal et al., 2011) and 3.8 copies of the 16S rRNA gene for all bacteria (Fogel et al., 1999). For the samples below 60 cm, the copy numbers decreased below the detection limit of the qPCR assay. The variety in anammox bacterial abundance in the soil core was more or less similar to the result based on 16S rRNA gene from the same site (Zhu et al., 2011b). Little significant correlation was observed between the abundance of anammox bacteria and see more environmental factors (Table 2). Similar to the anammox in stratified water columns and sediments where active anammox was restricted to specific layers (Dalsgaard et al., 2003, 2005), anammox bacteria seemed to prefer

selective niches at particular depths in soil (Humbert et al., 2010). Owing to the high interfering background in soil samples, only the primers targeting the 16S rRNA gene were capable for the in situ quantification of soil sample until now (Hamersley et al., 2007; Hu Lepirudin et al., 2011; Zhu et al., 2011b). As the specificity and sensitivity of 16S rRNA gene detection are highly dependent on the abundance of anammox bacteria in environmental samples (Song & Tobias, 2011), the hzsB gene would be a more precise biomarker for the quantification of anammox in soil. To analyze the community structure of n-damo bacteria on a functional level, primers targeting the pmoA gene were used in samples from representative depths (0–10, 20–30, 40–50, and 60–70 cm). The n-damo-specific pmoA primer A189_b was combined with the widely applied cmo682 primer (Holmes et al., 1995; Luesken et al., 2011c). Following by a nested PCR approach (cmo182-cmo568) (Luesken et al., 2011c), sequences clustering with the pmoA sequence present in the genome of M.