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Scientists discover DNA robbery in bacteria


How bacteria kill competitors in order to reach their resistance

Predatory bacteria - sounds like a dark science fiction scenario, but a study by the Biozentrum of the University of Basel documented that this behavior is real in bacteria. The research team led by Professor Marek Basler shows in the study that bacteria not only develop resistance to antibiotics themselves, but can also steal other bacteria with the help of poison. The results were published in the "Cell Reports" magazine.

The researchers were able to document how some bacteria injected their competitors with a poison cocktail, which caused them to burst. The attackers then took up the genetic material that had become available. In this way, the University of Basel said in a press release that bacteria can collect resistance without having trained them themselves. The winner of the bacterial attack could then multiply undisturbed. This mechanism is particularly problematic in hospitals, where numerous germs circulate and various antibiotics are used, to which resistance is therefore more common.

Multi-resistant bacteria can be fatal

If such multidrug-resistant bacteria multiply undisturbed, they can become a deadly danger for patients because antibiotics no longer work. According to the researchers at the University of Basel, this development is sometimes a consequence of the frequent and often careless use of antibiotics. The unnecessary use of antibiotics contributes to the fact that resistance is spreading faster and faster.

The Iraqi germ as an example of multi-resistance

The bacterium Acinetobacter baumannii is a typical hospital germ. In the Iraq war, multi-resistant bacteria of this type caused difficult-to-treat wound infections in American soldiers. This is why this bacterium is colloquially referred to as the "Iraqi germ". The model organism of the study was Acinetobacter baylyi, a close relative of the Iraqi germ. In the study, Professor Marek Basler's team identified five poison proteins, so-called effectors, which act differently. "Some of these toxic proteins kill the enemy very effectively, but do not destroy the cell," explains Basler. Other toxic proteins would only damage the cell envelope to such an extent that the attacked bacteria burst and genetic material leaked out.

What happens after the poison raid?

According to the study, the aggressor ingested DNA fragments after a successful attack. If there are genes on the fragments that are responsible for a certain resistance, the new owner will also become resistant. As a result, an antibiotic to which resistance has been developed is no longer effective and the germ can reproduce largely undisturbed.

Multi-resistance also with infectious agents

"A set of different effectors can also be found in other infectious agents such as the pneumonia pathogen or the cholera pathogen," says Basler. However, not all poison proteins would work equally well, since many bacteria have developed or acquired antidotes, so-called immunity proteins. The immunity proteins of the five effectors that were documented in the study were also identified. It made sense for the attackers not only to produce a single poison protein, but a cocktail of various toxins with different modes of action. “This increases the likelihood that the opponent can be successfully eliminated and, in some cases, that the cell's DNA also becomes available,” explains Basler. (fp)

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