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Ammonia‐oxidizing B acteria of the N itrosospira cluster 1 dominate over ammonia‐oxidizing A rchaea in oligotrophic surface sediments near the S outh A tlantic G yre

2015; Wiley; Volume: 7; Issue: 3 Linguagem: Inglês

10.1111/1758-2229.12264

1758-2229

Lorenzo Lagostina, Tobias Goldhammer, Hans Røy, T. Evans, Mark A. Lever, Bo Barker Jørgensen, Dorthe Groth Petersen, Andreas Schramm, Lars Schreiber,

Methane Hydrates and Related Phenomena

Summary Sediments across the N amibian continental margin feature a strong microbial activity gradient at their surface. This is reflected in ammonium concentrations of < 10 μM in oligotrophic abyssal plain sediments near the S outh A tlantic G yre compared with ammonium concentrations of > 700 μM in upwelling areas near the coast. Here we address changes in apparent abundance and structure of ammonia‐oxidizing archaeal and bacterial communities ( AOA and AOB ) along a transect of seven sediment stations across the N amibian shelf by analysing their respective ammonia monooxygenase genes ( amoA ). The relative abundance of archaeal and bacterial amoA (g −1 DNA ) decreased with increasing ammonium concentrations, and bacterial amoA frequently outnumbered archaeal amoA at the sediment–water interface [0–1 cm below seafloor (cmbsf)]. In contrast, AOA were apparently as abundant as AOB or dominated in several deeper (> 10 cmbsf), anoxic sediment layers. Phylogenetic analyses showed a change within the AOA community along the transect, from two clusters without cultured representatives at the gyre to N itrososphaera and N itrosopumilus clusters in the upwelling region. AOB almost exclusively belonged to the N itrosospira cluster 1. Our results suggest that this predominantly marine AOB lineage without cultured representatives can thrive at low ammonium concentrations and is active in the marine nitrogen cycle.