Borrelia bacteria move like corkscrews to infect hosts through tick and louse bites

Gardening · Published 3 October 2026 Swipe more like this →

In short: Borrelia are spiral-shaped bacteria that navigate their environment using internal filaments, propelling themselves forward in a distinct corkscrew motion. While famous for causing Lyme disease, these versatile organisms also trigger relapsing fever, utilizing a complex network of ticks and lice to jump between hosts and infiltrate human bloodstreams.

The genus Borrelia, named after French biologist Amédée Borrel, comprises 52 known species categorized primarily into Lyme disease groups, relapsing fever groups, and a distinct group found in reptiles. These bacteria are classified as Gram-negative, although their unique structure—featuring an outer membrane, an inner membrane, and a periplasmic space containing peptidoglycan—makes them difficult to visualize with standard Gram staining. Instead, they are typically observed using dark-field microscopy, where they appear as bright white spirals against a dark background.

Movement is achieved through endoflagella, or axial filaments, located within the periplasmic space. By rotating these filaments between the outer membrane and the peptidoglycan layer, the bacteria generate their characteristic corkscrew propulsion. Virulence is further supported by outer surface proteins (Osp) embedded in the outer membrane. Most species are obligate anaerobes, though some exhibit aerotolerance, and they are generally 20 to 30 micrometers long.

Transmission dynamics vary significantly by species. Lyme disease is spread exclusively by hard ticks of the family Ixodidae, which typically require 36 to 48 hours of attachment to successfully transmit the bacteria. In contrast, relapsing fever is often associated with soft ticks of the family Argasidae or, in the case of Borrelia recurrentis, the human body louse. While the U.S. Centers for Disease Control and Prevention notes a lack of credible evidence for lice as carriers, other research highlights how these vectors facilitate the spread of bacteria through co-feeding or direct contact with human mucous membranes.

Clinical diagnosis for human infection relies on two-tiered serological testing, including immunoassays and immunoblotting. Because Borrelia species are highly diverse—with some species like Borrelia miyamotoi uniquely transmitted by the same hard-shell Ixodes ticks that carry Lyme disease—understanding the specific vector and bacterial strain is essential for managing the distinct clinical presentations of these zoonotic diseases.

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