| Abstract |
All cultivated ammonia-oxidizing archaea (AOA) within the Nitrososphaera cluster (former soil group 1.1b) are neutrophilic. Molecular survey also indicates broad existence of Nitrososphaera-like phylotype in acid soil, but its ecological role is poorly understood. In this study, we present molecular .. [more] evidences for chemolithoautotrophic growth of the Nitrososphaera-like AOA in an acid soil with pH 4.92 using DNA-based stable isotope probing (SIP). Soil microcosm incubations demonstrated that nitrification was stimulated by urea fertilization and accompanied by significant increase in abundance of AOA rather than ammonia-oxidizing bacteria (AOB). Real-time PCR analysis of amoA genes as a function of buoyant density of DNA gradient following ultracentrification of the total DNA extracted from SIP microcosms indicated substantial growth of soil AOA during nitrification. Pyrosequencing of the total 16S rRNA genes in the ‘heavy’ DNA fractions suggested that archaeal and nitrite-oxidizing bacterial communities were labeled to a much greater extent than soil AOB. Acetylene inhibition further showed that 13CO2 assimilation by nitrifying communities depended solely on ammonia oxidation activity, suggesting chemolithoautotrophic lifestyle. Sequencing analysis of both amoA and 16S rRNA genes revealed that the 13C-labeled AOA were phylogenetically closely related to neutrophilic strains Nitrososphaera viennensis EN76 and JG1 within the Nitrososphaera cluster. Our results provide strong evidence for the adaptative growth of Nitrososphaera-like AOA in acid soil, suggesting a greater metabolic versatility of soil AOA than previously appreciated. [less]
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FTP
