title: High diversity of ammonia-oxidizing archaea in permanent and seasonal oxygen-deficient waters of the eastern South Pacific.
abstract: The community structure of putative aerobic ammonia-oxidizing archaea (AOA) was explored in two oxygen-deficient ecosystems of the eastern South Pacific: the oxygen minimum zone off Peru and northern Chile (11°S-20°S), where permanent suboxic and low-ammonium conditions are found at intermediate depths, and the continental shelf off central Chile (36°S), where seasonal oxygen-deficient and relatively high-ammonium conditions develop in the water column, particularly during the upwelling season. The AOA community composition based on the ammonia monooxygenase subunit A (amoA) genes changed according to the oxygen concentration in the water column and the ecosystem studied, showing a higher diversity in the seasonal low-oxygen waters. The majority of the archaeal amoA genotypes was affiliated to the uncultured clusters A (64%) and B (35%), with Cluster A AOA being mainly associated with higher oxygen and ammonium concentrations and Cluster B AOA with permanent oxygen- and ammonium-poor waters. Q-PCR assays revealed that AOA are an abundant community (up to 10(5) amoA copies ml(-1) ), while bacterial amoA genes from β proteobacteria were undetected. Our results thus suggest that a diverse uncultured AOA community, for which, therefore, we do not have any physiological information, to date, is an important component of the nitrifying community in oxygen-deficient marine ecosystems, and particularly in rich coastal upwelling ones.
authors.affiliation: Departamento de Oceanografía and Centro de Investigación Oceanográfica en el Pacífico Sudoriental, Universidad de Concepción, Casilla 160-C, Concepción, Chile. vemolina@udec.cl
authors.forename: Verónica
authors.initials: V
authors.lastname: Molina
authors.forename: Lucy
authors.initials: L
authors.lastname: Belmar
authors.forename: Osvaldo
authors.initials: O
authors.lastname: Ulloa
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D001105:Archaea / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D020562:Betaproteobacteria / Q000235:genetics; D002677:Chile; D019641:DNA, Archaeal / Q000235:genetics; D019766:Genes, Archaeal; D005838:Genotype; D009584:Nitrogen / Q000032:analysis; D010088:Oxidoreductases / Q000235:genetics; D010100:Oxygen / Q000032:analysis; D010140:Pacific Ocean; D010568:Peru; D010802:Phylogeny; D012623:Seawater / Q000032:analysis / Q000382:microbiology*; D014871:Water Microbiology
chemical_list: D019641:DNA, Archaeal; D000641:Ammonia; D010088:Oxidoreductases; C045582:ammonia monooxygenase; D009584:Nitrogen; D010100:Oxygen