Abstract
Microbial oxidation of ammonia controls the rate of nitrification in the majority of soils. Both nitrification rate and the composition of communities of ammonia oxidising archaea (AOA) and ammonia oxidising bacteria (AOB) are influenced by drought, with evidence that AOA are more sensitive to periods of drought than AOB. This has been explained by greater sensitivity of AOA to ammonia concentration, which will increase in soil solution during drought, but an alternative, previously unexplored explanation, is greater sensitivity of AOA to matric and/or osmotic stress. A soil microcosm experiment was designed to distinguish these different explanations in which AOA and AOB abundances (amoA abundance) and nitrification rate were measured over 28 days in nine treatments corresponding to all combinations of three soil matric potentials and three initial ammonia concentrations. Comparison of amoA abundance dynamics suggested that AOA were more susceptible to reduced matric potential than AOB, irrespective of soil ammonia concentration. The greater sensitivity of soil AOA to osmotic stress was also tested in 10-day cultures of representative strains of AOA and AOB in liquid medium containing different concentrations of NaCl and sorbitol as osmo-inducer. AOA were significantly more sensitive to osmotic stress than AOB. These results provide evidence for greater sensitivity of AOA than AOB to both components of water stress, matric and osmotic potential, representing an additional niche differentiation between these two essential groups of ammonia oxidisers.
Original language | English |
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Pages (from-to) | 184-190 |
Number of pages | 7 |
Journal | Soil Biology and Biochemistry |
Volume | 129 |
Early online date | 17 Nov 2018 |
DOIs | |
Publication status | Published - 1 Feb 2019 |
Bibliographical note
MOB was supported by a University of Aberdeen Elphinstone Scholarship and by TETFund through Adekunle Ajasin University Akungba (AAUA) Nigeria. CGR was funded by a Royal Society University Research Fellowship (UF150571) and CT by the Natural Environment Research Council (NERC, NE/L006286/1) and AXA Chair in Ecosystem Engineering and Microbial Ecology.Keywords
- Ammonia oxidising archaea
- Ammonia oxidising bacteria
- Drought
- Matric potential
- Osmotic potential
- Soil nitrification