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C penicillin
Alexander Fleming, a Scottish physician-microbiologist is best known for his discovery of penicillin in 1928. He was awarded the Nobel Prize in physiology and medicine along with Boris Chain and Howard Florey for the discovery of penicillin and its curative effect in various infectious diseases.
While experimenting on Staphylococcus bacteria, the culture sample got contaminated with mould spores, and he observed that the bacteria culture in proximity to mould colonies were dying. This led him to isolating the mould and identify it as a member of penicillium genus (Penicillium notatum), eventually leading to the discovery of the first antibiotic “penicillin”.
Streptomycin is the antibiotic that was originally isolated from the bacteria Streptomyces griseus; primarily used as a part of multi-drug treatment of pulmonary tuberculosis.
Neomycin is the class antibiotic that is originally isolated from the metabolic product of Streptomyces fradiae. Which inactivates the bacterial DNA polymerase by binding to the 30S ribosomal subunit causing misreading of genetic code to produce lethal protein.
Gentamycin is another class of antibiotic that was discovered and isolated from bacterium Micromonospora purpurea. It also kills bacteria by inhibiting the synthesis of bacterial protein by irreversibly binding to the 30S subunit of the bacterial ribosome.