How Ticks Protect Themselves From Deadly Bacteria

Ticks should fear us as much as we fear them.

In the lab, scientists discovered, that ticks contain a bacterial resistant protein, Dae2, that gives ticks immunity to skin microbes. This raised two questions "why do ticks require protection from human bacteria"? and "what specific bacteria does Dae2 target on the human skin?".

Scientists placed the Dae2 protein in a dish with common types of bacteria. After observation and imaging, Scientists discovered that Dae2 wards off Bacillus subtilis, a soil microbe, as well as Staphylococcus epidermidis and Corynebacterium propinquum, two bacteria that commonly reside on the human face and hands.

Scientists then bred ticks with a KO of the Dae2 gene, to observe how skin microbes affected ticks with a Dae2 deficiency. When these treated ticks were introduced to S. epidermidis and Corynebacterium propinquum, 70% of the treated ticks died within 8 hours of exposure.

Our skin microbes are lethal to ticks when the Dae2 protein is deficient or absent. It is still unknown how ticks will respond to Staphylococcus bacteria in nature. The Dae2 protein is produced in the tick's tongue and saliva so if the tick came into contact with Staphylococcus bacteria through any non-oral ingestion, it could be possible that the ticks would die just as they did with the lab.

Additional questions that have also arisen from this research are "what amount of Staphylococcus bacteria is lethal to ticks?" As well as, "how can Staphylococcus bacteria genetically evolve to avoid detection by the Dae2 protein?".

Citations:

B.M. Hayes et al. Ticks resist skin commensals with immune factor of bacterial origin. Cell. Published online December 10, 2020. doi: 10.1016/j.cell.2020.10.042.

S. Chou et al. Transferred interbacterial antagonism genes augment eukaryotic innate immune function. Nature. Vol 518, February 5, 2015, pg. 98. doi: 10.1038/nature13965.