Scientists have examined in detail the structure that bacteria use to make decisions
Biologists from the University of Illinois presented a report on the mechanism that bacteria responsible for chemotaxis - a motor reaction caused by external stimuli. The structure of this structure, which is vaguely reminiscent of the sense organs and nervous system of organisms, has been studied in detail at the molecular level.
Bacteria are able to move towards substances attractive to them (usually these are nutrients - sugars, amino acids), and move away from repelling substances (fatty acids, alcohols). At the same time, bacteria are very sensitive, and are able to respond to changes in the concentration of substances by 0.1%. In addition, bacterial receptors are able to respond to light.
“There are thousands of receptors on the surface of a bacterium that scan the environment and tell the bacteria what to do,” explains Professor Klaus Schulten. The process resembles the functioning of the sensory organs in higher animals, with the exception of the fact that bacteria do not have a central nervous system. Nevertheless, they are able not only to respond to external stimuli, but also to use the mechanism of vestigial memory, which allows them to survive.
Surface receptors transmit information to a deeper layer of proteins, called a kinase, which interprets the data obtained, on the basis of which it gives the commands “continue moving” or “change direction”. In the latter case, this kinase transfers the chemical command to another kinase, which directly controls the movement of the bacterial flagellum.
Early attempts to study the principles of functioning of the aforementioned molecular structure using electron microscopes and crystallography came up against the imperfections of these technologies - in particular, their low resolution. The authors of the work created a technology that allows you to clean the key proteins of the structure, and combine them so that they are collected in thin layers. As a result, it was possible to obtain clear three-dimensional images of both their spatial arrangement and interaction with each other.
A specially developed computer simulation complex, which worked on the Blue Waters supercomputer, built a three-dimensional model of the system based on simulations of the reactions of each atom in the structure and data obtained by various methods. The resulting model explains in detail the interaction between the parts of the chemosensory structure.
A new, improved view of how the structure works provides many answers and raises many new questions. How the signal passes from receptors to kinase, the interaction scheme of all components of the chemotaxis system - all this remains to be studied. Schulten compares this process of cognition with the study of complex mechanical watches.
“To understand the operation of a mechanical system, we need to find out its structure,” he says. - When we open the watch and see how the gears are connected with each other, we can begin to reflect on the principle of the watch. And we already know how gears are connected in the “brain” of bacteria. ”