title: Nitric oxide scavengers differentially inhibit ammonia oxidation in ammonia-oxidizing archaea and bacteria.
abstract: Differential inhibitors are important for measuring the relative contributions of microbial groups, such as ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA), to biogeochemical processes in environmental samples. In particular, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO) represents a nitric oxide scavenger used for the specific inhibition of AOA, implicating nitric oxide as an intermediate of thaumarchaeotal ammonia oxidation. This study investigated four alternative nitric oxide scavengers for their ability to differentially inhibit AOA and AOB in comparison to PTIO. Caffeic acid, curcumin, methylene blue hydrate and trolox were tested onNitrosopumilus maritimus, two unpublished AOA representatives (AOA-6f and AOA-G6) as well as the AOB representative Nitrosomonas europaea All four scavengers inhibited ammonia oxidation by AOA at lower concentrations than for AOB. In particular, differential inhibition of AOA and AOB by caffeic acid (100 μM) and methylene blue hydrate (3 μM) was comparable to carboxy-PTIO (100 μM) in pure and enrichment culture incubations. However, when added to aquarium sponge biofilm microcosms, both scavengers were unable to inhibit ammonia oxidation consistently, likely due to degradation of the inhibitors themselves. This study provides evidence that a variety of nitric oxide scavengers result in differential inhibition of ammonia oxidation in AOA and AOB, and provides support to the proposed role of nitric oxide as a key intermediate in the thaumarchaeotal ammonia oxidation pathway.
authors.affiliation: Department of Biology, University of Waterloo, 200 University Ave. W. Waterloo, ON N2L 3G1, Canada.
authors.forename: Laura A
authors.initials: LA
authors.lastname: Sauder
authors.affiliation: Department of Biology, University of Waterloo, 200 University Ave. W. Waterloo, ON N2L 3G1, Canada.
authors.forename: Ashley A
authors.initials: AA
authors.lastname: Ross
authors.affiliation: Department of Biology, University of Waterloo, 200 University Ave. W. Waterloo, ON N2L 3G1, Canada jneufeld@uwaterloo.ca.
authors.forename: Josh D
authors.initials: JD
authors.lastname: Neufeld
mesh_terms: D000641:Ammonia / Q000037:antagonists & inhibitors / Q000378:metabolism*; D001105:Archaea / Q000187:drug effects* / Q000378:metabolism*; D001419:Bacteria / Q000187:drug effects* / Q000378:metabolism*; D001557:Benzenesulfonates / Q000494:pharmacology; D001565:Benzoates / Q000494:pharmacology; D020562:Betaproteobacteria / Q000187:drug effects / Q000378:metabolism; D002109:Caffeic Acids / Q000494:pharmacology; D002839:Chromans / Q000494:pharmacology; D003474:Curcumin / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D058465:Nitrification; D043370:Nitrosomonas europaea / Q000187:drug effects / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D010802:Phylogeny; D012988:Soil Microbiology
chemical_list: D001557:Benzenesulfonates; D001565:Benzoates; D002109:Caffeic Acids; D002839:Chromans; D007093:Imidazoles; C079393:1,3-dihydroxy-4,4,5,5-tetramethyl-2-(4-carboxyphenyl)tetrahydroimidazole; D009569:Nitric Oxide; D000641:Ammonia; C414357:Methyl Blue; D003474:Curcumin; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid; C040048:caffeic acid
keywords: ammonia-oxidizing archaea; ammonia-oxidizing bacteria; nitric oxide; nitrification inhibitors