Microbes are very useful to combat disease-causing harmful bacteria. A number of antibiotics have been isolated from microorganisms. An antibiotic is a substance which in low concentration inhibits the growth and metabolic activity of pathogenic organisms without harming the host. Penicillin was the first antibiotic to be discovered by Alexander Fleming from fungus Penicillium notation. Antibiotics are obtained from lichens, fungi, eubacteria, and actinomycetes.

Some common antibiotics and their sources are as follows:

1. Polymyxin – Bacillus polymyxa

2. Chloramphenicol – Streptomyces venezuelae

3. Neomycin – Streptomyces fradiae

4. Tetracycline (Terramycin) – Streptomyces rimosus

5. Cephalosporin – Cephalosporium acremonium