title: PCR profiling of ammonia-oxidizer communities in acidic soils subjected to nitrogen and sulphur deposition.
abstract: Communities of ammonia-oxidizing bacteria (AOB) were characterized in two acidic soil sites experimentally subjected to varying levels of nitrogen and sulphur deposition. The sites were an acidic spruce forest soil in Deepsyke, Southern Scotland, with low background deposition, and a nitrogen-saturated upland grass heath in Pwllpeiran, North Wales. Betaproteobacterial ammonia-oxidizer 16S rRNA and ammonia monooxygenase (amoA) genes were analysed by cloning, sequencing and denaturing gradient gel electrophoresis (DGGE). DGGE profiles of amoA and 16S rRNA gene fragments from Deepsyke soil in 2002 indicated no effect of nitrogen deposition on AOB communities, which contained both Nitrosomonas europaea and Nitrosospira. In 2003, only Nitrosospira could be detected, and no amoA sequences could be retrieved. These results indicate a decrease in the relative abundance of AOB from the year 2002 to 2003 in Deepsyke soil, which may be the result of the exceptionally low rainfall in spring 2003. Nitrosospira-related sequences from Deepsyke soil grouped in all clusters, including cluster 1, which typically contains only sequences from marine environments. In Pwllpeiran soil, 16S rRNA gene libraries were dominated by nonammonia oxidizers and no amoA sequences were detectable. This indicates that autotrophic AOB play only a minor role in these soils even at high nitrogen deposition.
authors.affiliation: School of Biological Sciences, University of Aberdeen, Aberdeen, UK. c.schmidt@abdn.ac.uk
authors.forename: Christoph Stephan
authors.initials: CS
authors.lastname: Schmidt
authors.forename: Kristine A
authors.initials: KA
authors.lastname: Hultman
authors.forename: David
authors.initials: D
authors.lastname: Robinson
authors.forename: Ken
authors.initials: K
authors.lastname: Killham
authors.forename: James I
authors.initials: JI
authors.lastname: Prosser
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000145:classification; D009584:Nitrogen / Q000494:pharmacology*; D043369:Nitrosomonadaceae / Q000145:classification / Q000187:drug effects / Q000378:metabolism*; D043370:Nitrosomonas europaea / Q000145:classification / Q000187:drug effects / Q000378:metabolism; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry / Q000145:classification; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012336:RNA, Ribosomal, 16S / Q000737:chemistry / Q000145:classification; D012606:Scotland; D012988:Soil Microbiology; D013455:Sulfur / Q000494:pharmacology*; D014852:Wales
chemical_list: D001426:Bacterial Proteins; D012336:RNA, Ribosomal, 16S; D013455:Sulfur; D000641:Ammonia; D010088:Oxidoreductases; C045582:ammonia monooxygenase; D009584:Nitrogen