title: Ammonia-limited conditions cause of Thaumarchaeal dominance in volcanic grassland soil.
abstract: The first step of nitrification is carried out by ammonia-oxidizing bacteria (AOB) and archaea (AOA). It is largely unknown, by which mechanisms these microbes are capable of coexistence and how their respective contribution to ammonia oxidation may differ with varying soil characteristics. To determine how different levels of ammonium availability influence the extent of archaeal and bacterial contributions to ammonia oxidation, microcosm incubations with controlled ammonium levels were conducted. Net nitrification was monitored and ammonia-oxidizer communities were quantified. Additionally, the nitrification inhibitor allylthiourea (ATU) was applied to discriminate between archaeal and bacterial contributions to soil ammonia oxidation. Thaumarchaeota, which were the only ammonia oxidizers detectable at the start of the incubation, grew in all microcosms, but AOB later became detectable in ammonium amended microcosms. Low and high additions of ammonium increasingly stimulated AOB growth, while AOA were only stimulated by the low addition. Treatment with ATU had no effect on net nitrification and sizes of ammonia-oxidizing communities suggesting that the effective concentration of ATU to discriminate between archaeal and bacterial ammonia oxidation is not the same in different soils. Our results support the niche-differentiating potential of ammonium concentration for AOA and AOB, and we conclude that ammonium limitation can be a major reason for absence of detectable AOB in soil.
authors.affiliation: Department of Microbial Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen 6708 PB, the Netherlands Institute of Environmental Biology, University of Utrecht, 3584 CH, Utrecht, the Netherlands daebeler@microbial-ecology.net.
authors.forename: Anne
authors.initials: A
authors.lastname: Daebeler
authors.affiliation: Department of Microbial Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen 6708 PB, the Netherlands.
authors.forename: Paul L E
authors.initials: PL
authors.lastname: Bodelier
authors.affiliation: Institute of Environmental Biology, University of Utrecht, 3584 CH, Utrecht, the Netherlands.
authors.forename: Mariet M
authors.initials: MM
authors.lastname: Hefting
authors.affiliation: Department of Microbial Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen 6708 PB, the Netherlands Institute of Environmental Biology, University of Utrecht, 3584 CH, Utrecht, the Netherlands.
authors.forename: Hendrikus J
authors.initials: HJ
authors.lastname: Laanbroek
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D064751:Ammonium Compounds / Q000378:metabolism; D001105:Archaea / Q000378:metabolism*; D001419:Bacteria / Q000378:metabolism*; D065948:Grassland; D058465:Nitrification / Q000502:physiology*; D010084:Oxidation-Reduction; D012987:Soil; D012988:Soil Microbiology; D013890:Thiourea / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D064751:Ammonium Compounds; D012987:Soil; C009842:allylthiourea; D000641:Ammonia; D013890:Thiourea
keywords: allylthiourea; ammonia-oxidizing archaea; ammonia-oxidizing bacteria; ammonium; nitrification