Q.79 Which of the following genus is/are a spirochete(s)?
(A) Borrelia
(B) Leptospira
(C) Spirulina
(D) Treponema

Answer: (A), (B), and (D)

Spirochetes belong to the phylum Spirochaetota, featuring Gram-negative, helical bacteria with axial filaments for motility. Borrelia, Leptospira, and Treponema genera are classified as spirochetes, while Spirulina is not.​

Option Analysis

Borrelia: This genus includes spirochetes causing Lyme disease and relapsing fever, transmitted by ticks or lice, and belongs to the family Spirochaetaceae.​

Leptospira: Pathogenic species in this genus cause leptospirosis, a zoonotic disease; they are spirochetes in the family Leptospiraceae with hooked ends.​

Spirulina: This genus consists of cyanobacteria (blue-green algae), not spirochetes, used as a nutritional supplement despite superficial spiral shape similarity.​

Treponema: The primary spirochete genus causing syphilis (T. pallidum), yaws, and related diseases, in the family Spirochaetaceae.​

The question “which genus is a spirochete” frequently arises in competitive exams like CSIR NET Life Sciences, testing knowledge of bacterial classification. Spirochetes (phylum Spirochaetota) are distinctive Gram-negative, motile bacteria with helical shapes and endoflagella, causing diseases like syphilis and Lyme disease. This article breaks down Borrelia, Leptospira, Spirulina, and Treponema to clarify which qualify as spirochetes.​

Spirochete Characteristics

Spirochetes feature tight coils (3-500 μm long), axial filaments for corkscrew motility, and thrive in liquid environments like blood or water. Major families include Spirochaetaceae (Treponema, Borrelia) and Leptospiraceae (Leptospira). Pathogenic spirochetes evade immunity, leading to relapsing infections.​

Borrelia as Spirochete

Borrelia species, like B. burgdorferi (Lyme disease) and B. recurrentis (relapsing fever), are classic spirochetes in Spirochaetaceae. Transmitted by ticks/lice, they cause bull’s-eye rashes and joint issues.​

Leptospira as Spirochete

Leptospira, in Leptospiraceae, includes hooked-end spirochetes causing leptospirosis via animal urine exposure. Divided into pathogenic (L. interrogans) and saprophytic species.​

Why Spirulina is Not a Spirochete

Spirulina appears spiral but belongs to Cyanobacteriota (cyanobacteria), photosynthetic algae rich in proteins and vitamins, not pathogenic bacteria. Often confused due to morphology, but lacks axial filaments.​

Treponema as Spirochete

Treponema, notably T. pallidum (syphilis), is a Spirochaetaceae spirochete transmitted skin-to-skin, progressing from chancres to neurosyphilis if untreated. Diagnosed via dark-field microscopy.​

Key Phrase: which genus is a spirochete

For CSIR NET aspirants, remember: Borrelia, Leptospira, Treponema are spirochetes; Spirulina is cyanobacteria.​