An anonymous reader quotes a report from Phys.Org: Bacteria form the largest biomass in the world, larger than all the animals and plants combined, and they are constantly moving, but their movement is chaotic. The researchers [at the Niels Bohr Institute, University of Copenhagen, in collaboration with groups in U.S. and U.K.] pursued the idea that if this motion could be controlled, they might be able to develop it into a biological tool. They used a liquid crystal to dictate the direction of the bacterial movement, and added a microscopic cargo for the bacteria to carry, more than five times the size of the bacteria.
Assistant Professor Amin Doostmohammadi at the Niels Bohr Institute explains that in the past, there have been attempts to control the behavior of bacteria. But he and his colleagues adopted a novel approach: “We thought to ourselves, how about we create a track for the bacteria? The way we do that experimentally is to put the bacteria inside a liquid crystal. The trick is that a liquid crystal is not like a crystal, nor is it a liquid, it is somewhere in between. Each molecule in the crystal has an orientation, but doesn’t have a positional order. This means that the molecules can flow like a liquid, but they can also align like a crystal at the same time. […] Strong jets of bacteria moving in a designated direction without fluctuations is the great outcome of the experiment, according to Amin Doostmohammadi. What usually happens if the jets of bacteria are strong enough to be useful, the concentration of bacteria has to be high, and instabilities typically start to appear. The jet becomes unstable and chaotic. But in the liquid crystal pattern, the instabilities can be largely suppressed and prevent the bacterial jets from becoming chaotic. The pattern dictates the direction. This means it is possible to create jets of bacteria strong enough to carry strings of microscopic cargo, each piece of cargo five times the size of the bacteria themselves.
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