Bacterial cells are able to sense and move towards light by acting like microscopic eyeballs, according to scientists.
It has long been known that tiny bacteria are able to detect and respond to light in order to survive, but researchers in London claim that there is now evidence that the microbes focus light in much the same way as the human eye.
Studying the single-celled pond slime Synechocystis, researchers were able to attract the microorganisms to the source of a laser beam that they shone across the surface of a dish of bacteria.
The team observed that incoming rays of light were bent by a bacterium’s spherical surface and focused onto a point at the back of the cell.
Bacteria then move in the opposite direction to this point, bringing them closer to the light, which they can harness, for photosynthesis for energy and growth.
Researchers at Queen Mary University of London say that this system of detection is surprisingly similar to how light is focused by the cornea of the eye onto the light-sensitive retina.
This means that the findings are likely to have determined a key point of convergence in the evolution between single celled bacteria and more complex multi-cellular organisms like humans and animals that have camera-type eyes.
Professor Conrad Mullineaux, who led the research, said that the discovery was an exciting example of the evolutionary history of complex light sensing.
He commented: “Our observation that bacteria are optical objects is pretty obvious with hindsight, but we never thought of it until we saw it.
“No-one else noticed it before, either, despite the fact that scientists have been looking at bacteria under microscopes for the last 340 years.”
The researchers estimate that Synechocystis, which lives in water and on rocks and pebbles, can detect light to an angular resolution of 21 degrees, compared to an impressive 0.02 degrees in humans.
This suggests that the bacterium, which is about half a billion times smaller than a human eye, can only perceive a blurred outline of any sources of light it comes across.
Researchers are now interested to study the ability of non-spherical, rod-shaped bacteria to respond to light in the hope of learning more about how our eyes evolved.
The research was published in the journal eLife.
Image credit: Queen Mary University of London