A husband-and-wife research team at Vanderbilt University in Nashville recently discovered eerily spider-like DNA
hidden within an itsy-bitsy virus named WO.
The newfound DNA is somewhat similar to a portion of the gene that makes widow spiders venomous, according to a study published in the journal Nature Communications
"This is the first time we've seen a possible transfer of genetic information between an animal and a bacterial virus," said Seth Bordenstein, a biologist at the university who co-authored the study with his wife and lab partner, Sarah Bordenstein.
The new discovery may hold clues to how such viruses could be used as therapeutic tools.
Along came a spider
WO is a bacteriophage, a tiny virus that infects and replicates within bacteria. Its main target is the bacterial parasite Wolbachia
, which can live within black widow spiders and about 40% of the world's arthropods
Wolbachia had a recent claim to fame when scientists began using the bacterial strain to attack dengue- and Zika-carrying mosquitoes in an effort to curb the spread of mosquito-borne diseases
. Now that some secrets of WO's genetic makeup have been revealed, scientists could use that new insight to employ WO in making Wolbachia a more powerful weapon.
In other words, scientists could use the virus to insert whatever they want into Wolbachia. Wolbachia then would infect a mosquito and could modify or manipulate mosquitoes from within.
"We imagine inserting genes into Wolbachia that make it a more potent tool in the fight against mosquito-borne diseases," said Sarah Bordenstein, a senior research specialist at Vanderbilt.
For the study, the Bordensteins -- who have been studying WO for 15 years -- collected samples of the virus from insects infected with Wolbachia and sequenced its DNA.
As the researchers analyzed the newly sequenced genome, they discovered a web that was more tangled than expected.
"What stood out to us was that this phage, or virus of bacteria, harbored a few genes that were animal-like in length and seemingly composed of a few snippets of animal-like sequences. This is a virus, or phage, that first and foremost infects bacteria -- though the bacteria themselves live in symbiosis with various insects and other animals," Sarah Bordenstein said.
How the virus acquired this animal-like DNA remains a mystery, Seth Bordenstein added. It probably began with a spider.
"While the evidence suggests that phage WO may have acquired DNA from the spiders, rather than vice versa, we are still not completely sure of the origin. It is also possible that the sequences evolved in spiders and phage WO separately," he said.
'The advantage of a bacteriophage'
Phages are inherently mosaic, in the sense that they can acquire chunks of DNA from all kinds of places, said Ry Young, a professor at Texas A&M University and director of the university's Center for Phage Technology, who was not involved in the new study.
However, the study is the first time such a large segment of eukaryotic, or animal, DNA with intact genes has been discovered in a phage genome, Young said.
"I think the results are stunning," he said of the study. "I suspect that a lot of biologists are going to go back and look at their old phage sequences and discover they overlooked or didn't believe that some genes were on them."
Young added that the new study also might hold clues to how a bacteriophage could be used as a therapeutic tool
to treat bacterial infections in humans.
"In the past, phages have been thought of as bad candidates to use therapeutically against bacteria that propagate inside human cells," Young said. The new study, however, demonstrates otherwise and that a phage could get in and out of an animal cell and a bacterial cell to attack a possible illness.
"The advantage of a bacteriophage over chemical antibiotics is that there would be no side effects, since they would be targeted against the disease bacterium and would not kill the normal, and very important, bacteria in the human intestinal tract," he said.