title: Marine ammonia-oxidizing archaeal isolates display obligate mixotrophy and wide ecotypic variation.
abstract: Ammonia-oxidizing archaea (AOA) are now implicated in exerting significant control over the form and availability of reactive nitrogen species in marine environments. Detailed studies of specific metabolic traits and physicochemical factors controlling their activities and distribution have not been well constrained in part due to the scarcity of isolated AOA strains. Here, we report the isolation of two new coastal marine AOA, strains PS0 and HCA1. Comparison of the new strains to Nitrosopumilus maritimus strain SCM1, the only marine AOA in pure culture thus far, demonstrated distinct adaptations to pH, salinity, organic carbon, temperature, and light. Strain PS0 sustained nearly 80% of ammonia oxidation activity at a pH as low as 5.9, indicating that coastal strains may be less sensitive to the ongoing reduction in ocean pH. Notably, the two novel isolates are obligate mixotrophs that rely on uptake and assimilation of organic carbon compounds, suggesting a direct coupling between chemolithotrophy and organic matter assimilation in marine food webs. All three isolates showed only minor photoinhibition at 15 µE ⋅ m(-2) ⋅ s(-1) and rapid recovery of ammonia oxidation in the dark, consistent with an AOA contribution to the primary nitrite maximum and the plausibility of a diurnal cycle of archaeal ammonia oxidation activity in the euphotic zone. Together, these findings highlight an unexpected adaptive capacity within closely related marine group I Archaea and provide new understanding of the physiological basis of the remarkable ecological success reflected by their generally high abundance in marine environments.
authors.affiliation: Department of Civil and Environmental Engineering and.
authors.forename: Wei
authors.initials: W
authors.lastname: Qin
authors.affiliation: School of Oceanography, University of Washington, Seattle, WA 98195;
authors.forename: Shady A
authors.initials: SA
authors.lastname: Amin
authors.affiliation: Department of Civil and Environmental Engineering and.
authors.forename: Willm
authors.initials: W
authors.lastname: Martens-Habbena
authors.affiliation: Department of Civil and Environmental Engineering and.
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Walker
authors.affiliation: Department of Marine and Ecological Sciences, Florida Gulf Coast University, Fort Myers, FL 33965; and.
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Urakawa
authors.affiliation: School of Oceanography, University of Washington, Seattle, WA 98195;
authors.forename: Allan H
authors.initials: AH
authors.lastname: Devol
authors.affiliation: School of Oceanography, University of Washington, Seattle, WA 98195;
authors.forename: Anitra E
authors.initials: AE
authors.lastname: Ingalls
authors.affiliation: Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089.
authors.forename: James W
authors.initials: JW
authors.lastname: Moffett
authors.affiliation: School of Oceanography, University of Washington, Seattle, WA 98195;
authors.forename: E Virginia
authors.initials: EV
authors.lastname: Armbrust
authors.affiliation: Department of Civil and Environmental Engineering and dastahl@u.washington.edu.
authors.forename: David A
authors.initials: DA
authors.lastname: Stahl
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D001105:Archaea / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D017753:Ecosystem; D006863:Hydrogen-Ion Concentration; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010802:Phylogeny; D019642:RNA, Archaeal / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D054712:Salinity; D012623:Seawater / Q000382:microbiology; D013696:Temperature
chemical_list: D019642:RNA, Archaeal; D012336:RNA, Ribosomal, 16S; D000641:Ammonia
keywords: ecophysiology; marine ammonia-oxidizing archaea; urea utilization
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