The chlorophyl pigments have long been believed to be the basis for all autotrophy/phototrophy on earth, and these pigments therefore pretty much prop up the rest of the food chain (including yours truly). We know eukaryotic algae have a range of ‘helper pigments’ – this is why red algae are red, and not (usually!) green, but these transfer energy to the chlorophyl system, rather than drive metabolic pathways directly.

In 2000 a new group of membrane based proteins the proteorhodopsins were discovered in some cyanobacteria (blue green algae). These were shown to have the ability to drive a trans-membrane proton pump using only sunlight. Initially believed to have a sensory function, the latest work published in PLoS Biology indicates that the proton gradient created by the pump can drive the ADP-ATP conversion, and so be used as a general energy source for the cell. The long and the short of it is that cyanobacteria that have proteorhodopsin survive starvation in sunlight better than those that don’t, implying strongly that the proteorhodopsin generates real nutritional value for the bacterium.

This paper reinforces my prejudice that the prokaryotes are advanced organisms. These little guys might not have gone in for massive cellular machinery, but the chemistry they can do is really top notch!

Gómez-Consarnau L, Akram N, Lindell K, Pedersen A, Neutze R, et al. (2010) Proteorhodopsin Phototrophy Promotes Survival of Marine Bacteria during Starvation.
PLoS Biol 8(4): e1000358.doi:10.1371/journal.pbio.1000358