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Relative abundance and diversity of ammonia‐oxidizing archaea and bacteria in the San Francisco Bay estuary

2008; Wiley; Volume: 10; Issue: 11 Linguagem: Inglês

10.1111/j.1462-2920.2008.01764.x

1462-2920

Annika C. Mosier, Christopher Francis,

Marine and coastal ecosystems

Summary Ammonia oxidation in marine and estuarine sediments plays a pivotal role in the cycling and removal of nitrogen. Recent reports have shown that the newly discovered ammonia‐oxidizing archaea can be both abundant and diverse in aquatic and terrestrial ecosystems. In this study, we examined the abundance and diversity of ammonia‐oxidizing archaea (AOA) and betaproteobacteria (β‐AOB) across physicochemical gradients in San Francisco Bay – the largest estuary on the west coast of the USA. In contrast to reports that AOA are far more abundant than β‐AOB in both terrestrial and marine systems, our quantitative PCR estimates indicated that β‐AOB amoA (encoding ammonia monooxygenase subunit A) copy numbers were greater than AOA amoA in most of the estuary. Ammonia‐oxidizing archaea were only more pervasive than β‐AOB in the low‐salinity region of the estuary. Both AOA and β‐AOB communities exhibited distinct spatial structure within the estuary. AOA amoA sequences from the north part of the estuary formed a large and distinct low‐salinity phylogenetic group. The majority of the β‐AOB sequences were closely related to other marine/estuarine Nitrosomonas ‐like and Nitrosospira ‐like sequences. Both ammonia‐oxidizer community composition and abundance were strongly correlated with salinity. Ammonia‐oxidizing enrichment cultures contained AOA and β‐AOB amoA sequences with high similarity to environmental sequences. Overall, this study significantly enhances our understanding of estuarine ammonia‐oxidizing microbial communities and highlights the environmental conditions and niches under which different AOA and β‐AOB phylotypes may thrive.