They reveal a mechanism by which bacteria avoid antibiotics

Researchers from the Molecular Microbiology Group of the Department of Genetics and Microbiology have verified that the alteration of the balance between two Salmonella enterica proteins in the presence of antibiotics leads to the disorganization of the structures that allow population movement, causing the cells of the Bacterial colony closest to the harmful drug level stop while the rest spread to areas where the antibiotic concentration is lower.

Bacterial populations move over surfaces in a coordinated manner in what is known as swarming, which allows them to increase the extent of organ and tissue colonization and the virulent effect of infection. This movement occurs thanks to the action of flagella and chemoreceptors, which are the systems responsible for identifying chemical compounds present in the environment, and which are anchored at the poles of their cells, forming highly organized structures -polar clusters. -, of which the CheW protein is part.

Researchers have shown that the presence of toxic compounds for bacteria, such as antibiotics, induces in them a cellular response known as the SOS system that causes an increase in the concentration of the RecA protein, which interferes with the distribution of CheW by altering the organizing chemoreceptors and stopping swarming movement.

The imbalance between the concentrations of both proteins causes the bacterial colony to avoid the areas of the surface that it is colonizing that present a harmful concentration of antibiotic, stopping the swarming movement in the areas closest to the drug and allowing the colonization of the rest of the surface.

The work also shows that if the dose of the antibiotic in that area is reduced to non-harmful levels, the decrease in the concentration of RecA, and the reestablishment of the balance with CheW, again allows the structuring of the chemoreceptors, restoring the swarm movement and, therefore, the colonization of that region.

The molecular balance between the two proteins is thus crucial for the formation of the polar clusters of chemoreceptors in the cells of the bacteria and their colonizing movement.

The results clearly show that bacterial populations move on surfaces using specific mechanisms such as the one described in this work to avoid contact with compounds that damage their DNA, the researchers indicate.

Salmonella enterica is a member of a bacterial group that includes numerous pathogenic species that cause diseases of the digestive and respiratory systems, as well as septicemia and systemic infections.

The work opens the doors to the design of new compounds that can neutralize this bacterial strategy, which reduces the efficiency of treatment with antibiotics.