Bacteria use a viral weapon against other bacteria

According to an international team of researchers, bacterial cells use both a virus – traditionally considered an enemy – and a prehistoric viral protein to kill other bacteria that compete for food, which could have implications for the future treatment of infectious diseases.

The team, led by Thomas Wood, chair of biotechnology and professor of chemical engineering at Penn State, found a discrepancy between two types of bacterial cells when they moved on agar plates, in a form of motility called "swimming" where the bacterium moves by rotating its flagella.

"It was a bit like if Alexander Fleming had noticed that bacteria were not growing near a mushroom when he had discovered penicillin in the 1920s," Wood said. "We then studied and discovered that the breach was caused by the destruction of cells by a virus, SW1, carried by only one of the strains."

Not only did the team discover that a bacterial cell is using the SW1 virus to kill the bacteria that are its competitors for food, but it has also discovered that the bacteria that carry the virus are in better shape and are not killed. as often as bacteria without the virus. In addition, they discovered that, for one bacterium to be able to use SW1, it needed a fossil protein from a bacterium from another virus, there are millions of # 39; years. They report on their results in a recent issue of Cell reports.

Wood explained that sometimes a virus enters a cell and hides in the chromosome until it is ready to attack and kill the cell. However, due to random mutations, a virus is sometimes blocked in the chromosome and can not be attacked. Nine viruses are thus trapped in the beneficial intestinal bacteria E. coli. To be activated and used by E. coli against other bacteria, the SW1 virus needs a protein, YfdM, derived from a virus that has been captured in the E. coli chromosome there is millions of years old.

In addition, the virus is used by the bacterium as an identifier.

"Bacteria are often thought to live on their own, but they can look for food in groups – to act as a group, they need to be able to distinguish themselves from other bacteria," said Wood. "In one type of social activity, bacterial cells secrete chemical signals to communicate, but now we show that bacterial cells use viruses to distinguish themselves from closely related bacteria."

If the bacteria does not detect the virus in the other bacteria, it identifies a competitor for food and releases it to kill its competition. Although the exact process of this process is not yet understood, it could have potential benefits for research and medicine.

"Understanding how cells compete is important," said Wood. "For example, in synthetic biology where many cells work together, you can make the cells you want to work for become dominant, and in medicine you can design better ways to fight infectious agents."

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