Despite solid, growing genomic evidence for bacteria practicing bacteriochlorophyll and rhodopsin-based dual phototrophy, direct physiological proof has been lacking for over a decade until Kopejtka et al. recently solved the puzzle in an Alpine psychrophilic bacterium. Here, I highlight conceptual developments and address an overlooked, ecologically important phototrophic byproduct - heat.
Keywords: bacteriochlorophyll; extreme environments; heat production; light-harvesting; phototrophic bacteria; xanthorhodopsin.
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