title: Nitrification of archaeal ammonia oxidizers in acid soils is supported by hydrolysis of urea.
abstract: The hydrolysis of urea as a source of ammonia has been proposed as a mechanism for the nitrification of ammonia-oxidizing bacteria (AOB) in acidic soil. The growth of Nitrososphaera viennensis on urea suggests that the ureolysis of ammonia-oxidizing archaea (AOA) might occur in natural environments. In this study, (15)N isotope tracing indicates that ammonia oxidation occurred upon the addition of urea at a concentration similar to the in situ ammonium content of tea orchard soil (pH 3.75) and forest soil (pH 5.4) and was inhibited by acetylene. Nitrification activity was significantly stimulated by urea fertilization and coupled well with abundance changes in archaeal amoA genes in acidic soils. Pyrosequencing of 16S rRNA genes at whole microbial community level demonstrates the active growth of AOA in urea-amended soils. Molecular fingerprinting further shows that changes in denaturing gradient gel electrophoresis fingerprint patterns of archaeal amoA genes are paralleled by nitrification activity changes. However, bacterial amoA and 16S rRNA genes of AOB were not detected. The results strongly suggest that archaeal ammonia oxidation is supported by hydrolysis of urea and that AOA, from the marine Group 1.1a-associated lineage, dominate nitrification in two acidic soils tested.
authors.affiliation: State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, Jiangsu Province, China.
authors.forename: Lu
authors.initials: L
authors.lastname: Lu
authors.forename: Wenyan
authors.initials: W
authors.lastname: Han
authors.forename: Jinbo
authors.initials: J
authors.lastname: Zhang
authors.forename: Yucheng
authors.initials: Y
authors.lastname: Wu
authors.forename: Baozhan
authors.initials: B
authors.lastname: Wang
authors.forename: Xiangui
authors.initials: X
authors.lastname: Lin
authors.forename: Jianguo
authors.initials: J
authors.lastname: Zhu
authors.forename: Zucong
authors.initials: Z
authors.lastname: Cai
authors.forename: Zhongjun
authors.initials: Z
authors.lastname: Jia
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D001105:Archaea / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D058645:Denaturing Gradient Gel Electrophoresis; D019766:Genes, Archaeal; D020459:Genes, rRNA; D006868:Hydrolysis; D058465:Nitrification; D009587:Nitrogen Isotopes / Q000032:analysis; D010084:Oxidation-Reduction; D010802:Phylogeny; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology; D014197:Trees / Q000382:microbiology; D014508:Urea / Q000378:metabolism*
chemical_list: D009587:Nitrogen Isotopes; D012987:Soil; D000641:Ammonia; D014508:Urea