Morphology of Spirochetes

Table of Contents

Spirochetes, also known as spirochaetes, are a distinct double-membrane, Gram-negative bacteria that have spiralled or helically-coiled cells. They are chemoheterotrophic in nature and range about 3-500 μm in length and 0.09 to 3 μm in diameter.

Classification of Spirochetes

Morphology and Characteristics

• The distinguishing feature of spirochetes is the presence of endoflagella, which are also known as axial flagella.
• The endoflagella are found at each pole of the bacteria arising from the periplasmic space. They extend the length of the cell by projecting backwards.
• The flagella gives shape to the bacterial cells and also imparts motions such as flexion and extension, rotatory movement along the length of the axis and translatory motion.
• Spirochetes undergo asexual reproduction by the means of transverse binary division.
• They are mostly found in liquid environments such as blood, lymph, water and mud.
• These bacteria are mostly anaerobic and free living, but many exceptions are there.
• Spirochetes have a diverse pathogenic capacity. They are known to cause diseases in humans.

Description

The class consists of 14 genera that are divided into 4 orders and 5 families. The three orders Brevinematels, Brachyspirales and Leptospirales each have one class: Brevinemataceae, Brachyspiraceae and Leptospiraceae, respectively. The fourth order Spirochaetales have two families: Borreliaceae and Spirochaetaceae.

Disease Causing Organisms

Genus Treponema

Treponema are short, thin spirochetes that have fine spirals and rounded or pointed ends. The species of the genus are known to cause the following diseases:

• T. pallidum causes venereal syphilis
• T. endemicum causes endemic syphilis
• T. pertenue causes yaws
• T. carateum causes pinta

Syphilis caused by T. pallidum is a sexually transmitted chronic bacterial infection that presents itself in three stages: primary, secondary and tertiary. It can also be caused due to occupational reasons, blood borne infections and congenital transfer.

The primary stage causes ulcers on the genitals that are extremely painful. The secondary stage manifests after 1-3 months of primary lesion, the symptoms include skin rashes, mucus patches in the oropharynx and condylomata at the muco-cutaneous junctions. The last or tertiary stage aneurysms and chronic granulomata.

Genus Borrelia

Borrelia is a large, motile spirochete with wide, irregular and open-shaped coils. They transmit diseases to vertebrate hosts by using hematophagous arthropods as vectors. The diseases caused by the genus include:

• B. recurrentis causes relapsing fever
• B. burgdorferi causes Lyme disease
• B. vincenti causes Vincent’s angina

Relapsing fever, as the name suggests, causes recurrent febrile paroxysms. The disease is of two types: louse-borne that is caused by B. recurrentis and endemic or tick-borne caused by B. hermsii, B. duttoni and B. parkeri.

Lyme disease is a bacterial infection that is transmitted to humans by the bite of blacklegged ticks. The primary stage is manifested as localised skin lesions after an incubation of 3 to 30 days. The secondary stage is presented as a disseminated infection which includes fever, arthralgia and headache. The last or the tertiary stage causes persistent infection along with chronic arthritis, encephalopathy and acrodermatitis.

Vincent’s angina is a necrotising infection in the tooth margins and gums that is caused due to imbalance in the flora of gums. The main symptoms of the infection include bleeding, swollen and painful gums along with ulcers, fever and bad breath.

Genus Leptospira

Leptospires are thin, delicate spirochetes that possess a large number of highly coiled spirals and hooked ends that look like umbrella handles. They are obligate anaerobes.

Leptospira interrogans are known to cause a zoonotic disease called leptospirosis. It is transmitted to humans via direct or indirect contact of water contaminated by urine of carrier animals. It is a mild febrile illness that causes rashes, fever, abdominal pain and jaundice. Complications in this disease can cause other serious infections.

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Also Read:

• Difference between Treponema, Borrelia and Leptospira
• Morphology and Different Shapes of Bacterial Cell
• The Most Interesting and Unbelievable Facts about Bacteria
• Bacterial Diseases in Humans