Bacteria: Role in Health and DiseaseAbout This Hardback Bacteria are the microscopic, prokaryotic, single celled organisms that are few micrometers in length and have different shapes. Bacteria are present in almost all the habitats including the extreme habitats such as radioactive waste, acidic hot springs and the deep biosphere of the Earths crust. Many species of bacteria are pathogenic and cause infectious diseases such as syphilis, leprosy, cholera, anthrax, bubonic plague, etc.