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
BPoD stands for Biomedical Picture of the Day. Managed by the MRC Clinical Sciences Centre the website aims to engage everyone, young and old, in the wonders of biomedicine. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.