Bacterial dual phototrophy was demystified.

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.