Penicillin is a narrow-spectrum antibiotic, obtained from fungus Penicillium chrysogenum aka Penicillium notatum. For the first time in history, Alexander Fleming, Professor of Bacteriology at St. Mary's Hospital in London discovered this true antibiotic as a serendipitous accident. Fleming's perceptions within the 1920s driven to the recognizable proof of penicillin, and the revelation of the philosophy by which Penicillium slaughtered other microbes, improving the way for the advanced time of antibacterial therapy. 

Penicillium chrysogenum, a filamentous fungus species of genus Penicillium. They mostly grow on damp or water damaged areas, decaying vegetation, and so on. It has seldom been detailed as a cause of human infection. This fungus is a significant source of beta lactam antibiotics most importantly Penicillin. The essential structure of penicillin, 6-aminopenicillanic acid, is characteristic of the lactam ring intertwined to a bigger ring structure to make a penam core that's the essential structure of all related to penicillin.

 Before the uses, and benefits of this chemical obtained by fungi, I want to correspond bacteria, its type and mechanism of action of this antibacterial drug. Bacteria are minute unicellular living organisms with simple structure which can be seen only under microscope and exist in diverse environment. According to Gram’s staining, they are classified as Gram positive and Gram negative. They can be beneficial (for e.g. fermentative bacteria) or harmful to human and animals as they can cause many diseases. For the treatment of bacterial diseases, it is necessary to administer antibacterial drugs via many routes (as preferred according to disease and drug nature) in the body. Antibiotics are the medicine that cure the bacterial diseases either by destroying bacteria or by inhibiting the growth of bacteria.

 As I already mentioned, Penicillin is a narrow spectrum antibiotic; it means only certain types of bacteria are killed by this drug. This is bactericidal, it destroys bacterial population by inhibiting cell wall synthesis of bacteria.it is used against most of the Gram-positive bacteria and Gram-negative cocci, different spirochetes, and Actinomycetes israeli. 

Like most medicines, Penicillin also have contraindications and risk groups. This is a prescription medicine. Also, because of naturally occurring medicine which is directly produced by fermentation of the fungi, chance of antibiotic resistance is also high. That’s why we should follow the accurate protocol advised by our doctor or clinician Not only the Penicillin, but also many antibiotics play crucial role to make human and animal environment free from bacterial infections. However, haphazard use and toxicity is always deleterious.

References:
http://www.ncbi.nlm.nih.gov/pubmed/7372662