Bacteria do not defend themselves against antibiotics only as individual cells, but also as a population. This is shown by research from Wageningen University & Research (WUR) and the University of Cologne. The researchers show that dying E. coli cells release enzymes that break down antibiotics. In doing so, they help the remaining bacterial population recover. The study has been published in the scientific journal PNAS.
Antibiotics have been used in medical care for about a century. They have greatly improved the treatment of bacterial infections. At the same time, antibiotic resistance has become a global problem. Many antibiotics are also much older than their medical use. Substances such as penicillin evolved in bacteria and other microorganisms over the course of evolution. Many of the mechanisms bacteria use to defend themselves against antibiotics have also existed for millions of years. In the new study, scientists from WUR and the University of Cologne investigated how bacteria of the species Escherichia coli defend themselves against beta-lactam antibiotics. This is the most widely used group of antibiotics, and includes penicillin.
An enzyme neutralises the antibiotic
The bacteria studied produce the enzyme beta-lactamase. This enzyme chemically breaks down beta-lactam antibiotics, preventing the antibiotic from working.
Shared senior author Arjan de Visser of the Laboratory of Genetics: “In the experiments, we saw that after an initial growth phase bacterial cultures began to die when they were exposed to the antibiotic. After some time, however, the population recovered and the bacteria continued to grow (see figure 1). This recovery began once the concentration of the antibiotic had fallen below a certain threshold through the action of beta-lactamase.”
The researchers show that the antibiotic concentration falls in two ways. Living bacteria can take up the antibiotic through their cell membrane and break it down inside the cell. In addition, beta-lactamase molecules are released into the surrounding environment when bacterial cells die. These released enzymes also break down the antibiotic.
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