Coral reefs, colored food, and huge bacteria

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Science  08 Sep 2017:
Vol. 357, Issue 6355, pp. 1012-1013
DOI: 10.1126/science.357.6355.1012-a

Surgeonfishes harbor huge bacteria that help digest seaweed.


Healthy coral reefs depend on grazing fishes, such as surgeonfishes and tangs, to supress blanketing algal growth. These fishes host a diversity of enormous Epulopiscium bacteria, which are visible to the naked eye. Using single-cell genomics on these uncultured organisms, Ngugi et al. monitored the bacteria's metabolic contribution to their host fish. Surgeonfishes are specialist feeders—some enjoy brown algae, whereas others have a taste for reds and greens. The range of algal polysaccharides consumed by the surgeonfishes is reflected in the range of carbohydrate-active enzymes, agarases, and alginate lyases produced by their giant symbionts. Hence, dietary specialism among surgeonfishes appears to have coevolved with the digestive talents of the Epulopiscium spp. that they harbor and, in turn, is reflected in their feeding ecology.

Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1703070114 (2017).

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