Bacteria use viruses to differentiate themselves from their competitors

"Now we show cells utilize viruses to distinguish themselves from closely related bacteria," researcher Thomas Wood said.

By Brooks Hays
Bacteria use viruses to differentiate themselves from their competitors
The photo shows a virus particle carried by some bacteria strains. The phage allows the bacteria to recognize itself and gain a competitive advantage over its competitors. Photo by Sooyeon Song and Missy Hazen

April 16 (UPI) -- Normally, bacteria and viruses are enemies, but new research suggests a viral infection can offer bacteria some benefits -- chiefly, the ability to distinguish friend from foe.

"This is the first evidence that cells can distinguish themselves from related competitors through the use of a virus," Thomas Wood, researcher at Pennsylvania State University, said in a news release. "The implications are that we should re-evaluate the relationship between a virus and its cellular host in that there are sometimes benefits to having a viral infection."


Scientists discovered the phenomenon after observing a stark demarcation line between two strains of the bacteria Escherichia coli K-12, but no such divide between identical clones.

The related rivals steered clear of one another, while the identical strains swam toward one another. To find out why, scientists surveyed 4,296 single-gene knockouts in the genome of Escherichia coli K-12. Researchers determined only one mutation caused the demarcation line to disappear.

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The mutation involved a gene that is used in viral replication. According to their analysis, the virus-related proteins produced by the gene allow for bacterial self-recognition.

Scientists were also able erase the demarcation line by silencing the bacteriophage genomes that have weaved their way into the bacteria's genome. These leftover viral genes don't produce active phage particles, nor do they rupture host cells.


When scientists exposed bacteria to a related virus, the old viral genes were activated and began producing phage particles for the new virus.

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The latest findings -- published Tuesday in the journal Cell Reports -- suggest the newborn particles help bacteria distinguish itself from closely related competitors.

The new virus and old viral genes allow bacteria to organize into groups. Their power in numbers allows the bacteria to bully competitors.

"Bacteria are frequently thought of as living individually, but in fact they can forage for food as groups," Wood said. "In order to act as a group, they must be able to distinguish themselves from other bacteria. In one type of social activity, when they communicate, bacterial cells secrete chemical signals to communicate. Now we show cells utilize viruses to distinguish themselves from closely related bacteria."

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Experiments showed the virus doesn't attack its host cells. Instead, the virus attacks other bacteria cells that don't carry the virus. The host helps the virus reproduce, and the virus takes out the bacteria's competitors.

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