Bacteria can defend themselves against antibiotics with the help of an enzyme released by dying cells, according to a study. This discovery helps scientists understand bacterial survival mechanisms and improve the effectiveness of antibiotics.

The team demonstrated that Escherichia coli (E. coli) bacteria can produce an enzyme that chemically breaks down the antibiotic, rendering it ineffective.

Because the enzyme is released particularly by dying bacteria, the researchers refer to this as "altruistic cell death," which ensures the survival of the population as a whole. These findings help explain bacteria's collective survival mechanisms, which, in turn, could contribute to improving the effectiveness of existing and future antibiotics.

The project was prompted by a discovery by the study's first author who demonstrated that although bacterial cultures initially die off when exposed to the antibiotic, they eventually recover and continue to grow unhindered.

The team investigated two strains of E. coli bacteria—pathogens responsible for urinary tract infections, among other conditions, as well as septicemia and hospital-acquired infections—and their response to beta-lactams, the most widely used class of antibiotics worldwide. The bacteria produce the enzyme beta-lactamase, which chemically breaks down the antibiotic.

As soon as the antibiotic's concentration fell below a threshold level as a result of enzymatic activity, the bacterial cultures began to recover. "Therefore, the death of some of the bacteria contributes significantly to the long-term survival of the population as a whole, which can be interpreted as an example of altruistic collective behavior," Krug says.