Painting with Photosensitive Bacteria
By using a genetically modified strain of Escherichia coli, researchers at the Sapienza Department of Physics and the National Research Council (CNR) Nanotechnology Institute were able to observe how these bacteria accumulate where there is less possibility of movement, just as urban traffic forms where the speed declines. The team exploited this characteristic to develop nearly perfect reproduction of complex images, such as Leonardo’s Monalisa.
Some bacteria, such as E. coli, are well known to be fantastic “swimmers.” In fact, they are capable of moving over distances ten times their length in less than a second thanks to propellers that are driven by a nano-electric motor. Normally, the bacteria recharge this motor through a process based on oxygen. However, some micro-organisms found in our oceans use light to power their movement thanks to a protein, proteorhodopsin, located on the cell surface, which acts as a solar panel. And in these cells, their swimming speed is determined by the intensity of the light source.
The research team exploited this particular characteristic to employ genetically modified E. coli to produce proteorhodopsin as a “living paint” and create microscopic portraits through light. Moreover, in order to improve the low resolution caused by the slow bacterial response to light stimuli, the researchers also developed iterative algorithms to design optimised luminous patters. This allowed them to transform homogeneous bacterial suspensions into nearly perfect reproductions of complex images.
“This study,” points out Research Coordinator Roberto di Leonardo, “opens up a range of research possibilities. From the point of view of materials science, the bacteria could be used to develop living microstructures that could be shaped with light and used, for example, as microsensors. Further applications could be used in micro-robotics and bio-medicine. The possibility of custom-tailoring the configuration of cells via light patterns could open up new strategies for the transportation and selection of individual cells in miniaturised labs.”