Cellular chain mail protects pathogenic bacteria from antibiotics

(ORDO NEWS) — Clostridia cells were covered with a dense protein “armor”, which does not allow antibiotics to penetrate inside.

Clostridioides difficile bacteria are common representatives of the intestinal microflora. Normally, they do not manifest themselves, but in the case of degradation of the local microbiota, for example, with the active use of antibiotics, they can spread, causing rectal colitis.

The treatment of this infection requires a certain set of new antibiotics: clostridia are resistant to most common drugs. However, they do not respond well to therapy.

One reason for this resistance may be the “cellular armor” that protects bacteria from penetration by even small molecules, including antibiotics. The same S-layer can save clostridia from the action of protein enzymes, with which the affected cells themselves try to attack them.

Cellular chain mail protects pathogenic bacteria from antibiotics 2

Scientists led by Paula Salgado from the University of Newcastle, using X-ray crystallography and electron microphotography, studied the structure of the main proteins of the S-layer – SlpA. The work showed that they form a dense network of links intertwined, as if in medieval chain mail.

Similar structures are known in other bacteria, but in Clostridia, the S-layer turned out to be especially dense. The gaps in it do not exceed ten angstroms in diameter, while usually they reach 30-100 angstroms. Only a few molecules are able to penetrate the holes in this strong but flexible “armor”.

Biologists have demonstrated the protective functions of the S-layer by obtaining cells with parts partially removed. Indeed, such bacteria became easy prey for the body’s most common defenses, such as the enzyme lysozyme, which is found in salivary and lacrimal fluid.

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