Watch bacterial 'vision' in action
Biologists say they have seen a tiny bacterium focusing light just like the lens of a camera - or a human eye.
When lit from one side, each aquatic microbe shows a bright spot on its opposite edge, where the light has been focussed by its single, spherical cell.
That bright spot triggers the bacteria to move in the other direction, towards the light, which they need for photosynthesis.
This time-lapse footage (numbers in top left show minutes and seconds) shows the bacteria moving towards a light, at the bottom of the screen.
When they run into a laser beam (red spot, centre) it creates a new bright spot on their forward side - driving the bugs backward.
The findings appear in the journal eLife.
09 Feb 2016