Question

These are a group of very small intra-cellular bacteria. They are transmitted by arthropod vectors. Some of the diseases caused by them are typhus, trench fever and Q fever. Name these organisms.

• A. Viroids
• B. Bacteriods
• C. Rickettsia
• D. Mycoplasma

Answer 1

The correct option is C Rickettsia

Rickettsia is a genus of nonmotile, Gram-negative, non spore-forming, highly pleomorphic bacteria that can be present as cocci (0.1 μm in diameter), rods (1–4 μm long), or thread-like (10 μm long). The term rickettsia, named after Howard Taylor Ricketts, is often used interchangeably for any member of the Rickettsiales. Being obligate intracellular parasites, the Rickettsia survival depends on entry, growth, and replication within the cytoplasm of eukaryotic host cells (typically endothelial cells). Rickettsia species are transmitted by numerous types of arthropod, including chigger, ticks, fleas, and lice, and are associated with both human and plant disease. Rickettsia bacteria do not cause rickets, which is a result of vitamin D deficiency. The majority of Rickettsia bacteria are susceptible to antibiotics of the tetracycline group.

So the correct option is 'rickettsia'.