Bacteria-infecting Virus Contains Genes for Black Widow Venom

Scientists have discovered that a virus that normally infects bacteria, called WO, contains animal-like DNA. The DNA sequences include one for black widow spider venom. The surprising findings were just published in the journal Nature Communications.

Bacteriophages are viruses that specifically target and infect bacteria. One such bacteriophage is WO, a virus that attacks Wolbachia bacteria. Bacteria in the Wolbachia genus infect insects and other arthropods, including spiders such as the black widow.

A team of researchers sequenced the genome of the WO bacteriophage. They were shocked to find DNA sequences that matched animal genes. While viruses have been known to harbor animal genes, this had never been seen in a bacteriophage. Bacteriophages often contain bacterial genes but never genes from eukaryotes such as plants and animals. WO contained genes from a variety of species, including the black widow. The virus contained an intact sequence that matched the DNA used for producing black widow venom. In addition, WO contained eukaryotic genes that would allow the virus to sense pathogens and better bypass a host’s immune system. These segments would not normally be present in a bacteriophage genome.

The team believes that WO acquired these eukaryotic genes through its host, Wolbachia. Wolbachia bacteria wedge into the membrane of the infected arthropod. In order to get to the bacteria, WO must pass through both the arthropod’s membrane and the bacterium’s membrane. While doing this, WO might be able to pick up both eukaryotic and bacterial genes. It can then incorporate these genes into its own genome and utilize them for functions such as defense.

The researchers were initially shocked to discover animal genes in a bacteriophage. Bacteriophages are viruses that only infect bacteria so should only contain bacterial genes. As scientists uncover more details about how WO works, they may be able to use the information to genetically manipulate Wolbachia bacteria. Wolbachia have already been known to prevent the spread of dengue fever and the Zika virus by infecting mosquito hosts. Researchers believe that manipulating the bacteria could help prevent both diseases.


Bordenstein et al. Eukaryotic association module in phage WO genomes from Wolbachia. Nature Communications (2016).

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