Virus pirates black widow venom, uses it as weapon

New Scientist reports on some information-age piracy taking place in the microscopic realm, where viruses seem to have hijacked spider venom to attack bacteria:

Viruses often steal genes from their hosts. But because bacterial viruses – also called bacteriophages – only attack bacteria, genes from other domains of life are usually beyond their reach. That would include higher organisms known as eukaryotes, which have cells that contain a nucleus.

WO, however, faces an unusual challenge: its targets are Wolbachia bacteria living within the cells of insects, spiders, and some other animals. That means that for it to infect new bacterial cells, WO has to escape not only from its existing Wolbachia host, but also from the eukaryotic cell – and then the virus particles have to evade the eukaryote’s powerful immune system.

Many viruses of eukaryotic cells co-opt genes from their hosts to help them do this. To see if WO could do the same, Sarah and Seth Bordenstein, microbiologists at Vanderbilt University in Nashville, Tennessee, sequenced its genome and studied the provenance of its genes.

They found several genes closely related to ones found in eukaryotes, including the gene for latrotoxin, the poison used by black widow spiders. It kills by poking holes in cell membranes, making it a plausible tool for a virus needing to escape from a eukaryotic cell. WO also had other genes like those in eukaryotes, and these may help it evade the immune system.

This is the first time eukaryotic genes have turned up in a bacterial virus. What’s more, the eukaryote genes make up almost half of WO’s genome.

“For a phage to devote about half its genome to these eukaryotic-like genes, they must be important to the phage function,” says Sarah Bordenstein. WO probably picks up the eukaryote DNA after breaking out of a Wolbachia cell into the animal cell.

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