Primeval Eye

Spotting a sunny place to swim is a highlight of the summer – but we may be sharing the water with millions of eyeball-shaped cyanobacteria. Shape isn’t the only thing they have in common with our peepers, though. Cyanobacteria (represented in green here) focus light from the outside world (purple) onto a spot on their insides (shown in blue). Human eyes use focused light to send visual signals to the brain; cyanobacteria react differently – with movement. Close to the blue-coloured focus point, tiny changes in the walls of the bacteria allow them to move towards the light, which they use for photosynthesis. The discovery of eye-like behaviour in bacteria millions of years older than the human race suggests that our eyes possibly evolved from a bacterial design. This eye-popping thought is worth bearing in mind while we avoid swimming with cyanobacteria this summer – they can lead to nasty infections when swallowed.

Written by John Ankers

John Ankers

Writer

A former researcher in systems biology, John is now an online biology tutor and professional coach supporting the wellbeing of scientists and NHS professionals. He's writing, too, of course.

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• Image courtesy of Ronald Kampmann, Karlsruhe Institute of Technology, Germany
• University of Freiburg, Germany and Queen Mary University of London, UK
• Image copyright held by original authors
• Research published in eLife, February 2016