Correct Option: C

Rickettsia are tiny obligate, intracellular parasites found in blood sucking insects like lices, mites, ticks. They were first observed by Ricketts in 1909 but it was properly described by Rocha-lime 1916, who named them as Rickettsia. They have mucopeptide cell wall with DNA as genetic material and are independent entity causing diseases like Q-fever, typhus etc.