Introduction:Biological soil crusts(BSCs)can dominate surface cover in dry lands worldwide,playing an integral role in arid land biogeochemistry,particularly in N fertilization through fixation and cycling.Nitrificati...Introduction:Biological soil crusts(BSCs)can dominate surface cover in dry lands worldwide,playing an integral role in arid land biogeochemistry,particularly in N fertilization through fixation and cycling.Nitrification is a characteristic and universal N transformation in BSCs that becomes important for the export of N beyond the microscopic bounds of the crust itself.The contribution of ammonia-oxidizing bacteria(AOB)in BSCs has been shown,but the role and extent of the recently discovered ammonia-oxidizing archaea(AOA)have not.Methods:We sampled various types of crusts in four desert regions across the western United States and characterized the composition and size of ammonia-oxidizing communities using clone libraries and quantitative PCR targeting the amoA gene,which codes for the ammonia monooxygenase enzyme,universally present in ammonia-oxidizing microbes.Results:All archaeal amoA sequences retrieved from BSCs belonged to the Thaumarchaeota(Nitrososphaera associated Group I.1b).Sequences from the Sonoran Desert,Colorado Plateau,and Great Basin were indistinguishable from each other but distinct from those of the Chihuahuan Desert.Based on amoA gene abundances,archaeal and bacterial ammonia oxidizers were ubiquitous in our survey,but the ratios of archaeal to bacterial ammonia oxidizers shifted from bacterially dominated in northern,cooler deserts to archaeally dominated in southern,warmer deserts.Conclusions:Archaea are shown to be potentially important biogeochemical agents of biological soil crust N cycling.Conditions associated with different types of BSCs and biogeographical factors reveal a niche differentiation between AOA and AOB,possibly driven by temperature.展开更多
基金We thank Moria Nagy and G.S.N.Reddy for sharing their experiences with crust archaea.We are grateful to the staff of Sevilleta and Jornada LTER sites as well as the National Park Service(Canyonlands N.P.and Organ Pipe N.M.)for providing sampling permits,guidance,and hospitality.Finally,we thank Scott Bingham for assistance with qPCR and sequencing.This research was funded by an NSF grant from the Biodiversity Surveys and Inventories Program and by a USDA grant from the Soil Processes Program to FGP.
文摘Introduction:Biological soil crusts(BSCs)can dominate surface cover in dry lands worldwide,playing an integral role in arid land biogeochemistry,particularly in N fertilization through fixation and cycling.Nitrification is a characteristic and universal N transformation in BSCs that becomes important for the export of N beyond the microscopic bounds of the crust itself.The contribution of ammonia-oxidizing bacteria(AOB)in BSCs has been shown,but the role and extent of the recently discovered ammonia-oxidizing archaea(AOA)have not.Methods:We sampled various types of crusts in four desert regions across the western United States and characterized the composition and size of ammonia-oxidizing communities using clone libraries and quantitative PCR targeting the amoA gene,which codes for the ammonia monooxygenase enzyme,universally present in ammonia-oxidizing microbes.Results:All archaeal amoA sequences retrieved from BSCs belonged to the Thaumarchaeota(Nitrososphaera associated Group I.1b).Sequences from the Sonoran Desert,Colorado Plateau,and Great Basin were indistinguishable from each other but distinct from those of the Chihuahuan Desert.Based on amoA gene abundances,archaeal and bacterial ammonia oxidizers were ubiquitous in our survey,but the ratios of archaeal to bacterial ammonia oxidizers shifted from bacterially dominated in northern,cooler deserts to archaeally dominated in southern,warmer deserts.Conclusions:Archaea are shown to be potentially important biogeochemical agents of biological soil crust N cycling.Conditions associated with different types of BSCs and biogeographical factors reveal a niche differentiation between AOA and AOB,possibly driven by temperature.
