Pacific Northwest marine sediments contain ammonia-oxidizing bacteria in the beta subdivision of the Proteobacteria

Abstract

The diversity of ammonia-oxidizing bacteria in aquatic sediments was studied by retrieving ammonia monooxygenase and methane monooxygenase gene sequences. Methanotrophs dominated freshwater sediments, while beta-proteobacterial ammonia oxidizers dominated marine sediments. These results suggest that gamma-proteobacteria such as Nitrosococcus oceani are minor members of marine sediment ammonia-oxidizing communities.

FIG. 1

Abundance of RFLP types in Puget Sound (A) and Wintergreen Lake (B) sediment clone libraries. Representative sequence types appear above each bar, and the phylogenetic affiliations and functional gene types are shown.

FIG. 2

Neighbor-joining phylogenetic tree of derived amoA and pmoA amino acid sequences. Major proteobacterial lineages are denoted. Trees are based on comparison of 163 amino acids. This figure also contains sequences from clone libraries constructed from sediment samples collected from the Washington continental margin. Bootstrap values from 100 resamplings are shown, except for those nodes with values below 50 or where branching orders between the consensus tree and this tree were inconsistent.