Syphilis causing bacterium Treponema pallidum to belong to the group
A. Rickettsiae
B. Bacillus
C. Actinomycetes
D. Spirillum

Hint: Syphilis is a bacterial infection that is spread by sexual contact and it first appears as a painless sore which is caused by certain species of bacterium. It is a rigid spiral which is Gram-negative in nature and has constantly external amphitrichous or lophotrichous flagella that are called Spirillum. Examples include members of the genus Spirillum.

Complete Answer:
- Syphilis develops in different stages and each stage has a unique symptom. During the first stage, the appearance of a painless sore on the genitals, mouth, or rectum takes place. After the healing of the initial sore, the second stage is characterized by a rash. No symptoms appear until the final stage which may occur after many years. This final stage may lead to damage to the brain, nerves, eyes, or heart. Syphilis is treated with the help of an antibiotic known as Penicillin. To complete the treatment not only the patient but the sexual partner should also be treated. It can also spread to someone who gets in contact with mucus released from sores.
Now let us talk about the bacterium Treponema pallidum.
- Treponema pallidum belongs to the spirochaete bacterium. It has various subspecies that cause diseases like syphilis, bejel, and yaws. It is transmitted only amongst humans. The shape of this bacterium is helically coiled and is a microorganism. The dimensions are somewhere between 6–15 μm in length and 0.1–0.2 μm in width.
- For T. pallidum subsp. palladium, humans are the only natural hosts. It has both inner and outer membranes; the outer membrane does not contain lipopolysaccharide and contains a paucity of integral membrane proteins and surface-exposed lipoproteins, it is also designated as “the stealth pathogen. It gets nutrients and food from its human host only which is not capable of synthesizing its food.

Hence, Option D is right. Syphilis is caused by the bacterium Treponema pallidum to belong to the group Spirillum.

Note: We all know that Syphilis is a sexually transmitted disease. Several other diseases have a similar mode of transmissions such as AIDS (acquired immune deficiency syndrome), Gonorrhea, and genital herpes.