Date: 14.12.2020

How some ticks protect themselves from deadly bacteria on human skin

Lyme disease-spreading arachnids co-opted an ancient bacterial gene to eliminate microbes

By Erin Garcia de Jesus

Ticks may have reason to be as wary of us as we are of them.

Bacteria that are potentially deadly to the bloodsuckers live on human skin. But a gene from bacteria that ticks incorporated into their genetic code around 40 million years ago helps protect the arachnids from those would-be microbial killers, a new study finds.

That gene makes a protein, called Dae2, that black-legged ticks (Ixodes scapularis­) can use to fend off microbial threats, researchers report December 10 in Cell. But it’s not an equal opportunity weapon. In a test tube, the protein doesn’t mess with bacteria that don’t bother the ticks, including Borrelia burgdorferi, the bacterial cause of Lyme disease.

The finding may explain how ticks can get past humans’ defenses to transmit disease through their bite, including Lyme disease, the most common tick-borne disease in North America (SN: 6/23/16).

The arachnids’ saliva harbors many bacteria-killing proteins. But few studies have analyzed how such proteins allow ticks to defend themselves from some microbes while retaining species that aren’t dangerous to the ticks, says Albert Mulenga, a vector biologist at Texas A&M University in College Station who was not involved in the study. Such studies could help scientists pinpoint the proteins crucial for tick feeding as well as disease transmission. Researchers may then be able to develop ways to interfere with these proteins, stopping ticks from spreading disease.

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