Molecular and isotopic evidence of the distribution of nitrogen-cycling microbial communities in the oxygen minimum zone of the Tropical Mexican Pacific

ABSTRACT Microbial communities play a central role in the N cycle of oceanic oxygen minimum zones (OMZs), such as in the Eastern Tropical North Pacific (ETNP). We explored the spatial distribution of the genetic potential for ammonia oxidation (amoA gene for bacteria and archaea), denitrification (n...

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Bibliographic Details
Published in:FEMS microbiology ecology 2019-10, Vol.95 (10), p.1
Main Authors: Pajares, Silvia, Soto-Jiménez, Martín F, Merino-Ibarra, Martín
Format: Article
Language:English
Subjects:
Abundance
Ammonia
Ammonium
AmoA gene
Archaea
Composition
Cycles
Denitrification
Distribution
Ecology
Genes
Hydrology
Isotopes
Microbial activity
Microbial colonies
Microbiology
Microbiomes
Microorganisms
NirK protein
Nitrate reduction
Nitrates
Nitrification
Nitrogen
Oxidation
Oxygen
Reduction
Spatial distribution
Upwelling
Water circulation
Water column
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Summary:ABSTRACT Microbial communities play a central role in the N cycle of oceanic oxygen minimum zones (OMZs), such as in the Eastern Tropical North Pacific (ETNP). We explored the spatial distribution of the genetic potential for ammonia oxidation (amoA gene for bacteria and archaea), denitrification (nirS and nirK), anaerobic ammonium oxidation (anammox) (hzo) and dissimilarity nitrate reduction to ammonia (DNRA) (nrfA) and their relationships with the hydrological variables and isotopic composition of nitrate in the ETNP off Mexico. Oxygen concentration, the availability of N chemical forms and the upwelling shaped the distribution of N cycling genes along the water column. The high abundance of N genes and the isotopic composition of nitrate suggest the N cycling is very dynamic in the OMZ core. The accumulation of nitrite, the high abundance of archaeal amoA genes, and the deviation of the N and O isotopes of nitrate from the expected 1:1 ratio for nitrate reduction in the upper portion of this OMZ indicate that nitrification is a relevant process that fuels the denitrifier community. Conversely, the high abundances of nitrate, ammonium and nrfA genes in the deeper layer indicate that DNRA is a crucial process enhancing anammox there. These results show the need for more detailed studies of the N processes in OMZs. The accumulation of nitrite, the high abundance of N cycling genes and the isotopic composition of nitrate indicate a very dynamic N cycling in the Mexican Pacific OMZ core.
ISSN:0168-6496
1574-6941
DOI:10.1093/femsec/fiz143