• August 26, 2022

Some E. coli set off viral grenades inside nearby bacteria

Some bacteria can trigger unexploded viral grenades in neighboring bacteria’s DNA.

Certain Escherichia coli bacteria, including some that live in human intestines, make a chemical called colibactin. That chemical awakens dormant viruses inside nearby bacteria, sometimes leading to their destruction, researchers report February 23 in citronel.

This type of biological warfare among bacteria hasn’t been described before. “It’s an interesting strategy, and it’s also a dangerous strategy,” says Heather Hendrickson, an evolutionary microbiologist at the University of Canterbury in Christchurch, New Zealand, who was not involved in the work.

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Colibactin producers must creep up on their bacterial enemies and trigger the unexploded ordinance hiding in the enemies’ DNA. Those grenades are prophages — bacteria-infecting viruses that have inserted themselves into their hosts’ DNA, where they hide out harmless and dormant until something triggers their awakening. That something, in this case, is DNA damage caused by colibactin.

When colibactin dings DNA, a bacterial repair system called the SOS response kicks in, chemical biologist Emily Balskus and colleagues found. “What many phages have done is to tap into that response,” says Balskus, a Howard Hughes Medical Institute investigator at Harvard University.

“It’s a signal for them to move out of this dormant lifestyle and awaken to kill their host and move on to find a new host,” she says. Once phages wake up, they replicate and burst out of the host cell, destroying it.

But once these viral grenades go off, they can infect other bacteria, potentially exposing the attacking bacteria and other close-by microbes to biological shrapnel.

Humans might also get caught in the cross fire. Researchers already knew that colibactin can cause damage to human DNA that may lead to colon cancer. But why the bacteria would use the chemical against people wasn’t known.

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