Bacteria turn gears
Researchers at the Argonne National Laboratory (Illinois), owned by the US Department of Energy, and Northwestern University (Evanston, Illinois), working under the leadership of Igor Aronson, have demonstrated that bacteria randomly floating in the medium can set in motion microscopic gears suspended in the medium.
Aronson argues that the ability to direct and use the energy of bacterial movement is very important for the development of hybrid microbial-driven biomechanical systems. He also notes that the microscopic size of the gears here is a relative concept: they are millions of times larger than the bacteria themselves.
During the experiments, the scientists placed microfoils with beveled teeth, the size of which was 380 microns, in a nutrient medium containing a popular object of research – the ubiquitous bacteria Bacillus subtilis. The movement of bacteria in the medium is chaotic, but they periodically collide with the teeth of gears and start their movement in a certain direction.
The figure shows a diagram of the experience, options for the shape of gears
and a schematic representation of the direction and speed of rotation
(one or two revolutions per minute, but this is not bad for bacteria).
To move one microstern, a total effort of several hundred bacteria is required. If two gears are placed in the medium, the teeth of which are connected as in a clockwork mechanism, the bacteria begin to rotate them in opposite directions, and such synchronous movement can be maintained for long periods of time. Here's what it looks like on a micrograph (accelerated 5 times):
A few more videos can be viewed in additional materials to the article "Swimming bacteria power microscopic gears", published on December 18 in the preliminary on-line version of the Proceedings of the National Academy of Sciences.
The rotation speed of the gears can be changed by changing the oxygen concentration in the medium. Oxygen is needed by bacteria to obtain energy due to the oxidation of nutrients, so a decrease in its concentration slows down the rotation of gears. The elimination of oxygen completely stops the rotation, which is restored when the oxygen supply to the system is resumed.
So far, all this looks like scientific fun, but, according to Aronson, the results of the work demonstrate that microscopically floating agents, such as bacteria or man-made nanorobots, in combination with solid materials, can make up a "smart material" capable of dynamically changing its structure, repairing damage or setting micromechanisms in motion.
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on Argonne National Laboratory: Argonne scientists use bacteria to power simple machines.
24.12.2009