Love of a microbe: data on the "communication" of bacteria will help in the fight against infections

Scientists have identified the molecular mechanism by which insect-pathogenic bacteria coordinate their behavior depending on the population size. The authors described a system of mutually influencing signaling proteins that regulate the activity of almost 300 genes in cells. The discovery will be useful in developing infection control methods, as many pathogens use similar systems to coordinate behavior. Read more about how managing the behavior of microbes will help medicine and agriculture in the Izvestia article.

How bacteria "communicate" with each other

Researchers from the Federal Scientific Center for Biological Systems and Agrotechnologies of the Russian Academy of Sciences (Orenburg) analyzed the genome, that is, the sequences of all genes, and the transcriptome, the sequences of all RNAs, of a certain strain of bacteria Chromobacterium subtsugae. These microorganisms are of particular interest to researchers. Despite the genetic similarity, some species of this genus, in particular Chromobacterium subtsugae, infect insects, while others, such as Chromobacterium violaceum, infect mammals, including humans. Therefore, they can be used to study the mechanisms underlying virulence in relation to completely different hosts, experts told Izvestia.

Project executor Ksenia Inchagova

Photo: Galimzhan Duskaev

As the scientists explained, many pathogenic bacteria coordinate their behavior using a special communication system — the so-called sense of quorum. This mechanism allows microbes to assess population density and synchronously activate genes responsible for virulence, that is, the ability to cause disease in the host body and the formation of biofilms (communities that bacteria create to increase resistance to adverse conditions and more effectively infect hosts).

Until now, it has remained unclear exactly how these microorganisms regulate their pathogenicity depending on environmental conditions, and in particular on population density. It is important to understand these processes, as this will potentially allow the development of new methods of fighting infections aimed not at destroying bacteria, but at disrupting their communication systems, the scientific center said.

Photo: Global Look Press/Jochen Tack

"The data obtained not only reveal the mechanisms of bacterial communication, but also provide new targets for potential effects on pathogenic microorganisms. For example, regulatory proteins can become targets: by suppressing them, it will be possible to block communication between bacteria and thereby prevent the development of infection," explained Galimzhan Duskaev, project leader, Doctor of Biological Sciences, First Deputy Director of the Federal Scientific Center for Biological Systems and Agrotechnologies of the Russian Academy of Sciences.

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The authors identified 296 genes whose activity changed (in some it increased, in others it decreased) when a critical cell density was reached. Biologists have also discovered a hierarchical mechanism that regulates the work of these genes.

The scientists compared the regulatory mechanism found in Chromobacterium subtsugae with that previously described in the closely related bacterium Chromobacterium violaceum, a mammalian pathogen. The analysis showed that the molecular systems regulating the "quorum sensing" in these species are very different. This explains their different pathogenicity. For example, in Chromobacterium subtsugae, the authors identified unique genes that are probably responsible for interaction with their host insects.

In the future, scientists plan to use plant metabolites — phytochemicals isolated from medicinal plants — capable of suppressing the processes of density-dependent communication in potentially pathogenic bacteria of the gastrointestinal tract of farm animals.

— Today, more than ever, it is important to develop approaches that reduce or completely eliminate the use of antibiotics in agriculture, but at the same time ensure an increase in productivity and an adequate level of protection for farm animals. One of the ways to solve the problem may be the use of feed additives that can control the sense of quorum of zoopathogenic bacteria, and subsequently change the microbiome and the directions of metabolic flows of the digestive system in a direction favorable for agricultural production, Galimzhan Duskaev said.

How bacteria are used in medicine and agriculture

The use of such bacteria can significantly reduce and optimize the amount of applied pesticides. Bacillus thuringiensis has been used as a natural pesticide for many years, moreover, in the 1990s, plant varieties carrying transgenic Bt toxin were created. And for many years now, such transgenic plants have been widely used abroad, Sergey Sedykh, a market expert at NTI Helsnet and a lecturer at Novosibirsk State University (NSU), told Izvestia.

Photo: IZVESTIA/Eduard Kornienko

— A few decades ago, no one would have thought about how modern genomic technologies would change our understanding of the effect of such bacteria on pathogenic insects and how they communicate with each other. Such studies make it possible to understand at the molecular level exactly how bacteria that are beneficial to humans and pathogenic to insect pests communicate with each other. In the future, such fundamental research will help solve many of the challenges facing agriculture today and ensure the country's technological sovereignty," the specialist noted.

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At the same time, a systematic analysis of bacterial behavior has another applied aspect — in medicine, which can assist in studying the behavior of bacteria that cause an exacerbation of the disease in humans, said the head of the Smart Supply Chain segment of the FoodNet working group NTI Sergey Kosogor.

— Many medical scientists note the detrimental effect of biofilms, which consist of bacterial cells, on the human body: they form stable colonies that secrete various substances, thus they protect the community from the effects, in this case of drugs, therefore, the study of the mechanism by which bacteria establish a connection and form a critical mass, which It hinders a person's recovery, which is very important," the expert emphasized.

Photo: IZVESTIA/Eduard Kornienko

Bacteria form quite complex communities. Biofilms formed by bacteria, forming complex structures, often cause chronic and recurrent infections, as well as reduce the effectiveness of antibacterial therapy. By using a variety of chemical signals to communicate with each other, the microorganisms have learned to perceive them as social signals telling them how things are going in the colony. This suggests that bacteria have a primitive "collective mind", and depriving them of this is an important task, it will destroy the bacterial population, said Sergey Kosogor.

The results of the study, supported by a grant from the Russian Science Foundation (RSF), are published in the journal Microorganisms.