In a surprise discovery, scientists have found that bacteria see the world in effectively the same way as humans, with bacterial cells acting as the equivalent of microscopic eyeballs.
British and German researchers made the finding by accident when studying aquatic cyanobacteria, which sometimes form a green film on rocks and pebbles. Scientists already knew the bacteria could perceive the position of a light source and move towards it – a phenomenon called phototaxis – but before now, no one understood how they did it.
“We noticed it accidentally, because we had cells on a surface and we were shining light from one side, in order to watch the movement towards the light,” microbiologist Conrad Mullineaux from Queen Mary University of London told Jonathan Webb at BBC News. “We suddenly saw these focused bright spots [inside the cells] and we thought, ‘bloody hell!’ Immediately, it was pretty obvious what was going on.”
What the researchers discovered when studying Synechocystis – a species of cyanobacteria found in freshwater lakes and rivers – is that their cell bodies act like a lens. When light hits the spherical surface of the cell, it refracts into a point on the other side of the cell. This triggers movement by the cell away from the focused internal spot, towards the source of the light, with the cells using tiny tentacle-like structures called pili to pull themselves forwards.