Emergency Lighting

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Science  04 Jun 2010:
Vol. 328, Issue 5983, pp. 1208
DOI: 10.1126/science.328.5983.1208-c

What happens when one's stores of energy run out? In vast and dilute oceans, high-energy nutrients can become quite scarce indeed, and many marine bacteria have the capacity to harvest energy directly from sunlight by means of light-activated proton pumps called proteorhodopsins. Nevertheless, the reasons for the widespread occurrence of proteorhodopsins and the fitness benefits of light-harvesting for bacteria have not been firmly established.

Gómez-Consarnau et al. cultured the Vibrio sp. AND4, knocked out its proteorhodopsin, starved it of organic detritus, and watched cell size shrink during the next 10 days. When the mutant was restocked with the missing gene and exposed to light again, it survived as well as the wild type, recovering to 3- to 6-fold higher cell densities than starved bacteria that had been left in the dark. It appears that proteorhodopsin fuels adaptive cell physiology and allows Vibrio to endure until more nourishment arrives. Although this study documents the evolutionary significance of bacterial proteorhodopsin, it does not yet explain the diversity of proteorhodopsins or their full ecological implications. More light is needed.

PLoS Biol. 8, e1000358 (2010).

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