Correct Option: D

Most bacteria that are associated with plants are actually saprotrophic, and do no harm to the plant itself. However, a small number, around 100 known species, are able to cause disease. Bacteria also cause diseases in animals and human beings. In humans, pathogenic bacteria cause infections such as tetanus, typhoid fever, diphtheria, syphilis, and leprosy. Among several, Leptospirosis is a bacterial disease that affects animals and humans.