METAGENOMICS REVEALS PHYLOGENETIC DIVERSITY AND DEPTH STRATIFICATION OF UNIQUE PROTEORHODOPSIN GENES IN SHALLOW VERSUS DEEP OCEAN WATERS AT STATION ALOHA
Proteorhodopsins (PRs) are light activated retinal-containing proton pumps highly expressed in marine bacterial communities. These molecules are globally distributed in the ocean’s photic zone and used for energy production, thus challenging our understanding of the contribution of heterotrophic bacteria to carbon cycling and energy flux in the sea. Here we investigate the phylogenetic diversity, distribution, and abundance of PR groups in the waters at station ALOHA. We utilize metagenomic data sets collected at multiple depths up to 1000 meters over one and a half years. PRs were identified at all depths but were most abundant at depths above 200 meters. The majority of PR gene sequences belong to SAR11. Several additional taxa including SAR324, Actinobacteria, Bacteroidetes, and giant viruses also possess PRs. We observed multiple variations in the conserved residues involved in ion pumping and spectral tuning, although two variations, predominantly from SAR11, were the most abundant. The DTE-Q motif, believed to be blue light activated proton pump associated, was found predominantly at depths of 200m and above. DTT-T on the other hand, is of unknown function and was found at depths of 200 meters and below. Additional variations were identified, often taxon specific, while others appear to cross taxonomic boundaries, likely due to horizontal gene transfer. Our data highlight the broader organismal distribution of different PR types as well as the within-taxon variability. These data provide the framework to understand the physiological relevance of unique PR sequences necessary to elucidate the details of energy flux by heterotrophic bacteria at station ALOHA.
Olson, D. K., University of Hawaii, USA, firstname.lastname@example.org
Mende, D. R., University of Hawaii, USA, email@example.com
Aylward, F. O., University of Hawaii, USA, firstname.lastname@example.org
DeLong, E. F., University of Hawaii, USA, email@example.com
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