The palirrhotrophic origin of energy metabolism.

It is proposed that the earliest cellular organisms relied upon a novel type of energy transduction termed palirrhotrophy, which generates a high-energy "currency" chemiosmotically by exploiting the rhythmic variations in salinity which occur in the estuarine environment. Calculations based on estimates of contemporary chemiosmotic transduction efficiency suggest that such a mechanism could produce usable energy in high yield. The minimum polypeptide requirement for palirrhotrophy compares favorably with that of a fermentative pathway. It is suggested that palirrhotrophic organisms exist today but are difficult to detect.