Microorganisms cause various types of infectious diseases in humans. Some of the examples of diseases caused by microbes are given below: Tuberculosis - is caused by bacteria called mycobacterium tuberculosis.AIDS - is caused by a virus called a retrovirus. It is a fatal disease.Pneumonia - is caused by various bacteria and viruses. The most important causative agent is klebsiella Intestinal Diseases - Most intestinal diseases are caused by e.coli and other bacteria Food poisoning is also a very common disease caused by bacteria.