A type of virus that only infects bacteria has stolen the DNA of black widow spiders to attack its prey. And just not any DNA, but the genes that code for spider venom. This is the first time we’ve seen a virus take genes from such a complex organism.
The virus, named WO, attacks Wolbachia, a bacteria that lives inside spiders and other insects. The virus’s job isn’t easy: WO has to infect the Wolbachia bacteria, break out of the bacteria, and finally break out of the insect host to find its way into another insect, and then into another Wolbachia, and so on.
To do this, WO stole a gene called latrotoxin that codes for black spider poison, according to Sarah and Seth Bordenstein, Vanderbilt University researchers who sequenced the WO genome and presented the results in a Nature study. Latrotoxin pokes holes in cell membranes, and WO probably uses latrotoxin to punch holes in its targets to make it easier to get out. Most likely, WO picks up the spider DNA after breaking out of a Wolbachia cell into the animal cell.
In almost all cases, viruses just steal genes from bacteria. Spiders are more complicated organisms than bacteria, so it’s a much bigger deal that WO was able to take those genes. "There hasn’t been another case of a latrotoxin being found outside of spiders," Seth told The Atlantic.