University of Michigan - Ann Arbor

Spirochetes are gram-negative bacteria characterized by long, spiral-shaped bodies that can reach lengths up to $${}250$$ μm. Due to their extreme thinness, they are difficult to view under conventional brightfield microscopes, typically requiring darkfield fluorescent microscopy instead, and are highly difficult or impossible to culture in a laboratory.

Spirochete

Which of the following best describes spirochete cells?

Which of the following statements is true about spirochete cells?

Which of the following diseases is commonly associated with spirochete bacteria?

What is a distinguishing feature of spirochete bacteria?

*Treponema* is a genus of spirochetes that contains several human pathogens, including the species *Treponema pallidum*, which is further divided into multiple subspecies causing syphilis and tropical diseases of the skin, bones, and joints.

*Treponema*

*Borrelia burgdorferi* is a pathogenic spirochete species that causes Lyme disease. It is transmitted to humans by tick vectors from the genera *Ixodes* and *Amblyomma*, and infection often produces a 'bull's eye' rash, fever, fatigue, and sometimes debilitating arthritis.

*Borrelia burgdorferi*

*Borrelia recurrens* is a pathogenic spirochete species that causes relapsing fever, a condition marked by recurring cycles of fever.

*Borrelia recurrens*

The axial filament is a specialized, flagellum-like structure that wraps around a spirochete cell. Unlike typical external flagella, it runs internally inside the cell body, residing in the periplasmic space between the outer membrane and the plasma membrane. The rotation of this internal filament is what enables the high motility of spirochetes.

Axial Filament

*Treponema pallidum* is a species of spirochete that is classified into four subspecies: *T. pallidum pallidum*, which causes the sexually transmitted infection syphilis, and three other subspecies (*T. pallidum pertenue*, *T. pallidum carateum*, and *T. pallidum endemicum*) that cause tropical infectious diseases affecting the skin, bones, and joints.

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