Marine microbes can utilize sunlight energy in a previously unknown way, driving sodium ions rather than protons across their membranes, reports a paper published in Nature Communications. The study presents a new approach by which microbes gain energy to fuel microbial growth.

Rhodopsins are distributed throughout marine microbes and the majority utilise light energy to pump protons across microbial membranes to create a proton gradient, which in turn can fuel ATP production. Hideki Kandori and colleagues investigate the function of the two rhodopsins from the marine flavobacterium Krokinobacter eikastus. They find that whilst one is a prototypical proton pump, the other’s main function is to pump sodium ions. This discovery not only expands our knowledge of the microbial repertoire of sunlight utilization, but may also contribute to the development of new clinical tools in which light can be used to control neurons.