Plant leaves convert light into chemical energy for use in cells. Their biochemistry specifically absorbs the blue and red areas of the visible light spectrum. Now researchers have discovered that light-harvesting bacteria living on the surfaces of leaves gather energy from the green part of the spectrum, meaning that they cooperate rather than compete with plants. How did this perfectly balanced energy-sharing system come about?

Knowing that light-harvesting microbes live in aquatic environments, the researchers tested the hypothesis that similar bacteria live on leaves. They were right. And the light that the microbes gather was “compatible with the plant’s photosynthesis,” resulting in “a significant ecological advantage to microbes inhabiting this environment.”1 In other words, bacteria take full advantage of all the green light that plants don’t use.

In a study published online in Environmental Microbiology, the research team screened genetic material from the surfaces of different leaves harvested from an oasis near the Dead Sea. They found genetic codes for specific types of rhodopsins, which are molecules that capture light. Some enable sight in vertebrate eyes, but many of the rhodopsins found on leaf surfaces were part of light-gathering apparatuses used by bacteria as tiny energy generators called “light-driven proton pumps.”1

The researchers found that the bacteria absorb the most light at exactly the same point where plants absorb no light. This way, more plant growth cooperatively provides more living space and fuel for the bacteria.

Charles Darwin proposed that natural selection developed all living systems through a “struggle for life.”2 He imagined that competition between creatures built new biological structures to make them more fit to survive. But the specific biochemicals of these plants and bacteria enable them to cooperate without competing.3….

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