Spirochaeta

Spirochaeta is a genus of bacteria in the family Spirochaetaceae, within the order Spirochaetales of the phylum Spirochaetes (also referred to as Spirochaetota in some classifications). Members are helical, flexible, slender cells that range about 0.2 to 0.5 micrometers in width and several micrometers in length. They are characterized by periplasmic flagella, or axial filaments, located between the cytoplasmic and outer membranes, which produce distinctive corkscrew motility.

Most Spirochaeta species are motile chemoorganotrophs, capable of anaerobic or microaerophilic growth. They are typically non-spore-forming and do not perform photosynthesis; some degrade organic matter in aquatic sediments and soils, contributing to nutrient cycling. They are generally Gram-negative in staining, though their cell envelope can appear atypical due to the location of flagella.

Ecology: They are widely distributed in freshwater and marine habitats, including sediments, biofilms, and animal-associated environments, often in communities with other bacteria. They do not commonly cause disease in humans; pathogenic spirochetes belong to other genera such as Treponema, Borrelia, and Leptospira.

Taxonomy and research: The genus Spirochaeta is one of several genera within Spirochaetaceae. Species classification relies on morphology, physiology, and molecular data. Spirochaeta species have historically served as model organisms for studying spirochete motility and periplasmic flagella.

Culture: Many Spirochaeta species are difficult to culture and require specialized anaerobic or microaerophilic media. They are often studied in environmental microbiology and microbial ecology, illustrating spiral morphology and unique motility strategies.