The corkscrew bacteria that use internal motors to drill through tissue

Health · Published 20 October 2026 · Updated 20 October 2026 Swipe more like this →

In short: Spirochaetes are among the most invasive pathogens known to science. Unlike most bacteria that swim using external tails, these organisms house their motors inside their bodies. This unique internal machinery allows them to twist like corkscrews, enabling them to navigate through viscous environments and penetrate deep into host tissues.

Spirochaetes belong to the phylum Spirochaetota and are characterized by their distinctive diderm (double-membrane) Gram-negative structure. Their most defining physical trait is their long, helically coiled cell bodies, which range from 3 to 500 μm in length. While many are free-living and anaerobic, several species are significant human pathogens, including those responsible for syphilis, Lyme disease, and leptospirosis.

The secret to their invasive nature lies in their endoflagella, also known as periplasmic flagella. These are anchored at the poles within the periplasmic space—the area between the inner and outer membranes. Because they are tucked inside, these filaments project backwards to extend the cell's length, creating a twisting motion. Recent research into the pathogen Leptospira has revealed that these filaments are encased in a multi-protein sheath consisting of 9 to 12 distinct proteins. This sheath allows the bacteria to adjust their curvature to suit their environment.

This modular core-sheath coupling is a sophisticated mechanical adaptation. For instance, the lower-curvature architecture used by Leptospira interrogans is essential for moving through viscous environments during infection. Furthermore, molecular markers like a three-amino-acid insert in the FlgC protein are shared by all Spirochaetota species, suggesting this unique internal flagellar structure is a fundamental evolutionary trait. These bacteria are so effective at niche adaptation that they have caused diverse diseases, from intestinal spirochaetosis to human periodontal disease.

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