These bacteria that change shape to avoid antibiotics

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New study shows how some bacteria can adapt to long-term exposure to antibiotics by changing their shape. The work has been published in the journal Physics of nature.

The problem of antibiotic resistance

For several decades, antibiotics have saved millions of lives by fighting bacteriological diseases. However, the fight is not won in advance. Nature is constantly adapting and, by dint of using this type of treatment, bacteria have evolved to develop resistance.

As a result, the means of struggle are less and less effective. Recently, researchers sounded the alarm, highlighting that urgent action was needed to control the use of antibiotics before they stopped working completely. Ultimately, the WHO also believes that these resistant bacteria could kill up to ten million people by 2050.

It is therefore becoming urgent to propose new approaches capable of preventing these infections. With this in mind, the researchers are closely analyzing the different strategies deployed by the bacteria concerned. Some are already known, such as that of lateral gene transfer, considered to be the main mechanism for the spread of resistance in bacteria. A team led by Shiladitya Banerjee of Carnegie Mellon University today describes a new adaptability.

Bacteria that make the “round back”

As part of this work, the researchers looked at how exposure to antibiotics could affect the growth and morphology of the bacteria. Caulobacter crescentus, a commonly used model organism. This study found that when exposed to non-lethal doses of chloramphenicol (a broad-spectrum antibiotic) over several generations, these bacteria can “Regain their pre-stimulus growth rate and undergo dramatic changes in cell shape”, write the authors.

To put it more simply, these bacteria began to radically change shape by curling in on themselves (after ten generations exposed to low doses of antibiotics). Once the antibiotics were removed, the cells then returned to their original shape after several generations.

The shape of the bacteria before (above) and after (below) exposure to antibiotics. Credit: Shiladitya Banerjee

From experiments done on a single cell, and thanks to theoretical modeling, researchers believe that increasing cell width (and therefore volume) helps dilute the amount of antibiotics inside the bacteria, while cell curve and width can lower the surface area to volume ratio, allowing less antibiotics to pass through the cell surface.

“This research is of great importance for human health. It will likely stimulate many other molecular studies on the role of cell form on bacterial growth and resistance to antibiotics.», Concludes Mr. Banerjee.

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