Summary Proteorhodopsin (PR) is a light‐driven proton pump that has been found in a variety of marine bacteria, including Pelagibacter ubique , a member of the ubiquitous SAR11 clade. The goals of this study were to explore the diversity of PR genes and to estimate their abundance in the North Atlantic Ocean using quantitative polymerase chain reaction (QPCR). We found that PR genes in the western portion of the Sargasso Sea c...

Summary To determine whether metagenomic libraries sample adequately the dominant bacteria in aquatic environments, we examined the phylogenetic make‐up of a large insert metagenomic library constructed with bacterial DNA from the Delaware River, a polymerase chain reaction (PCR) library of 16S rRNA genes, and community structure determined by fluorescence in situ hybridization (FISH). The composition of the libraries and comm...