One of Everything

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Science  18 Aug 2006:
Vol. 313, Issue 5789, pp. 893
DOI: 10.1126/science.313.5789.893a

Recent molecular analyses of marine microbes (see, for example, DeLong et al. Reports, 27 January 2006, p. 496) have documented how the environmental pressures of living in the ocean at depths down to several kilometers are reflected in the corresponding genomic complements. Derelle et al. provide the genome sequence of Ostreococcus tauri, a green alga of extraordinarily small size (about 1 μm in diameter) and remarkably high gene density. This picoeukaryote achieves the feat of packing over 8000 genes into less than 13 Mb by making the average gene just slightly longer than 1.2 kb and reducing the intergene distance to 0.2 kb. Nevertheless, it still contains entire plantlike metabolic pathways, such as the enzymes for C4 photosynthesis (an evolutionary adaptation to low CO2 levels) and for storing glucose as one large starch granule within the single chloroplast. Also appearing in only one copy each are the mitochondrion, a Golgi body, and the nuclear pore, which presumably reflect the physical advantages of small intracellular distances and a high surface-to-volume ratio. — GJC

Proc. Natl. Acad. Sci. U.S.A. 103, 11647 (2006).

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