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Environ Microbiol. 2010 Sep;12(9):2450-65. doi: 10.1111/j.1462-2920.2010.02218.x. Epub 2010 Apr 19.

High diversity of ammonia-oxidizing archaea in permanent and seasonal oxygen-deficient waters of the eastern South Pacific.

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1
Departamento de Oceanografía and Centro de Investigación Oceanográfica en el Pacífico Sudoriental, Universidad de Concepción, Casilla 160-C, Concepción, Chile. vemolina@udec.cl

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.

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