Innovation and digital technologies at the service of medicine and healthcareMany motile bacteria, such as Escherichia coli, continually explore the surrounding space in search of the best growth conditions.Like grazing animals, if left in an open space, the bacteria spread and distribute themselves evenly on the “lawns” wherever food is available.Gathering them is one of the most difficult responsibilities, especially when they are numerous and run fast.A group of researchers from the Physics Department of Sapienza has shown that microscopic spots of light, like thousands of sheepdogs, can gather even the fastest bacteria in a confined area.This is only possible if the bacteria are genetically modified to produce proteorhodopsin, a proton pump that, like a mini solar panel, uses light energy to move the flagella.The study, published in “Nature Communications”, is the result of Sapienza's collaboration with CNR-Nanotec and the Italian Institute of Technology.“These bacteria - explains Helena Massana-Cid, researcher at the Physics Department of Sapienza and first name of the study - move quickly when the light is intense and more slowly in dark areas.A computer-controlled light projector was then used to gather them, consisting of tiny reflectors aimed at individual cells, capable of quickly turning off the light on bacteria trying to escape from the collection area ”.Thanks to a digital camera associated with the microscope, the researchers obtained images of the suspensions of bacteria, which were processed in real time through geometric transformations, and then projected onto the sample with a fixed time delay.Thus, moving enlightened by this warped image of their past, thousands of bacteria can make their way together, like a pack, to a specific region.Particles capable of consuming energy to actively move, such as motile bacteria, are part of a large class of non-equilibrium systems, both synthetic and biological, collectively called "active matter".Although predicting and controlling the behavior of these systems is still an open challenge between physics and biology, this experiment paves the way for interesting developments both in the fundamental aspects of non-equilibrium physics and in its applications.“At a fundamental level - concludes Roberto Di Leonardo of the Department of Physics of Sapienza and coordinator of the study - we were able to establish a mathematical relationship between the geometric properties of the projected light patterns and the way in which bacteria respond by distributing themselves in space.As for future applications, light could be used to trap and transport clouds of active particles in miniaturized laboratories, which exploit mechanical energy to drive micro-machines with both biological and synthetic components ”.Tecnomedicina is a newspaper specialized in the topics of biomedical research, medicine and health, registered in the Press Register of the Court of Milan with n.286 of 11.28.2018Tecnomedicina is a product published by RBM Group Srls Via Domodossola, 7 - 20145 Milan VAT number: 10479500968 ROC registration n.32544To send communications, requests for information, press releases and reports or to get in direct contact with the editorial staff of Tecnomedicina, write to redazione@tecnomedicina.it