Full Sequence Ahead

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Science  27 Jan 2012:
Vol. 335, Issue 6067, pp. 382
DOI: 10.1126/science.335.6067.382-b

Some of the most abundant microorganisms in surface ocean communities are resistant to cultivation in the laboratory. Metagenome sequencing can reveal insights into the metabolism and physiology of such microbes, but the other ∼200 fully sequenced marine microbial genomes to date remain poor references for useful comparisons. To provide a better genomic context for uncultivated microbes, Dupont et al. used metagenomic reconstructions of Global Ocean Survey samples to generate two nearly complete genomes of SAR86 bacteria, a clade of ubiquitous nonphotosynthetic γ-proteobacteria. The authors also sequenced two partial genomes of single cells within the SAR86 lineage collected off the coast of San Diego, USA. The reconstructed genomes and single-cell genomes all suggest that SAR86 bacteria have stream-lined metabolisms: They cannot synthesize all of their required vitamins or amino acids and rely on specialized carbon sources. All four genomes also contain at least one gene encoding green light–tuned proteorhodopsin, which suggests that the organisms generate ATP via light-sensitive enzymes. The genomes vary significantly according to biogeography (i.e., sample locations and water temperatures), implying physiological differences. This broader genomic context may aid in future cultivation efforts.

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