The hzsB gene was identified as a proper biomarker to explore the anammox bacterial biodiversity and abundance in soil. The anammox bacteria were present throughout the soil core with the highest abundance of 2.7 × 106 hzsB copies g−1 dry soil at 40–50 cm and were not detectable below 70 cm. Sequences related to at least three species of known anammox bacteria, ‘Brocadia

anammoxidans’, ‘Brocadia fulgida’, and ‘Jettenia asiatica’ were detected. By combining the analysis of pmoA and 16S rRNA genes, the n-damo bacteria were observed to be present in 30–70 cm with abundance from Mitomycin C nmr 6.5 × 103 (60–70 cm) to 7.5 × 104 (30–40 cm) copies g−1 dry soil. The pmoA sequences retrieved from different depths closely related to each other and formed a unique clade. Our results showed that anammox and n-damo bacteria co-occurred in the paddy soil. Both of them were abundant in deep layers (30–60 cm) and the community structures changed along depths in the soil core. Ammonium () and methane (CH4) were previously assumed to be http://www.selleckchem.com/products/MDV3100.html inert under anoxic conditions

(Strous & Jetten, 2004; Jetten, 2008). This understanding was gradually changed by the discoveries of anaerobic ammonium oxidation (anammox) (Van de Graaf et al., 1995; Strous et al., 1999) and nitrite-dependent anaerobic methane oxidation (n-damo) (Raghoebarsing et al., 2006; Ettwig et al., 2009, 2010) in which and CH4 were oxidized anaerobically using nitrite as the electron acceptor. With the development of Forskolin mw molecular biomarkers (Kuypers et al., 2003; Schmid et al., 2005, 2008; Li et al., 2010, 2011; Li & Gu, 2011), anammox bacteria have been detected in many marine ecosystems (Kuypers et al., 2003; Byrne et al., 2009), freshwater ecosystems (Zhang et al., 2007; Zhu et al., 2010), and man-made environments (Quan et al., 2008; Zhu et al., 2011a). Using the isotopic pairing technology, anammox has been identified as an important process in the aquatic nitrogen

cycle, accounting for as much as 13% of N2 production in freshwater Lake Tanganyika (Schubert et al., 2006) and 67% in marine environments (Thamdrup & Dalsgaard, 2002). Although recently anammox bacteria were enriched from a peat soil (Hu et al., 2011), relative little is known about the distribution of anammox bacteria in soil ecosystems because of the lack of suitable primers for quantitative PCR assays and high interfering background in fluorescence in situ hybridization (FISH) analyses by soil matrix components. Hydrazine synthase is a key enzyme in the anammox metabolism, consisting of three subunits encoded by the genes hzsA, hzsB, and hzsC (Strous et al., 2006; Kartal et al., 2011; Harhangi et al., 2012), responsible for the synthesis of hydrazine from nitric oxide and ammonium (Kartal et al., 2011). Previously, the hzsA gene was used as an anammox phylomarker (Harhangi et al., 2012).