When Life Gives You Mold, Discover Penicillin

Science is a field that is unpredictable and challenging, yet fascinating. Throughout their careers, scientists have come face-to-face with successes, failures and rejections. They have put great amounts of dedication into projects and may have even experienced a light bulb moment when identifying a solution after working on a long problem. But imagine stumbling upon a miraculous medical discovery, as a total accident through pure luck. This situation is how you could describe the discovery of penicillin by Dr. Alexander Fleming in 1928.

Fleming was an esteemed bacteriologist who worked at St. Mary’s Hospital in England (Fleming, 1929). His research involved examining the nature of staphylococci in Petri dishes. One night, his assistant was placing the dishes away to incubate but she had neglected to properly cover a couple of the dishes (Böttcher, 1963). As a result, this allowed airborne fungus spores to makes its way into the broth contained in the Petri dishes (Böttcher, 1963). The following day, Fleming noticed one of the dishes contained the bacteria in addition to areas of clear agar with green fungus, as seen in Figure 1 (Wainwright, 1987). Some scientists would not think twice about this contamination error in their research, however what made Fleming a great scientist was his curiosity, strong observation skills and passion of understanding how things work. Fleming documented that it has appeared as though the cocci disappeared and idea of life inhibiting life was intriguing to him and motivated him to study the fungus (Böttcher, 1963).

Figure 1. A diagram from Fleming’s notes displaying a colony of penicillin inhibiting the growth staphylococcus bacteria on a Petri dish (Fleming, 1929).

Initially, antibiotics were not thought of to be used on humans until the 1940’s when Ernst Chain and Howard Florey experimented with this compound (Nicholas and Davies, 2012). In the 1950’s to 1960’s, scientists were focused on understanding the molecular mechanism of the drug and understanding its chemical structure. Beta-lactam antibiotics, such as penicillin, are capable of inhibiting the growth of bacteria as they target the synthesis of the peptidoglycan, the cell wall. During the normal synthesis of peptidoglycan, peptide chains are cross-linked with each other to form a strong structural cell wall using penicillin-binding proteins (PBPs) (Nicholas and Davies, 2012). Beta-lactam antibiotics will react with PBPs to form penicilloyl-enzyme complex which prevents the PBPs from producing crosslinks therefore the cell wall loses its structure and lyses (Nicholas and Davies, 2012).

Fleming’s serendipitous discovery has lead to many benefits in medicine and food production. However, antibiotic resistance has recently become an increasing public health issue as these industries are overusing antibacterial products. Scientists continue to search for and create new antibiotics and public health experts push governments to develop policies that regulate the distribution of antibiotics (Ontario Medical Association, 2013). Although the discovery of antibiotics has greatly contributed to science, it is crucial that we must use them wisely.


Böttcher, H.M., 1963. Miracle Drugs. Heinemann: London.

Fleming, A., 1929. On the Antibacterial Action of Cultures of a Penicillium, with Special Reference to Their Use in the Isolation of B. Influenza. The British Journal of Experimental Pathology. 10(3): 226-236. Available at: <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2048009/pdf/brjexppathol00255-0037.pdf>

Nicholas, R., Davies, C., 2012. Structural Mechanisms of β-Lactam Antibiotic Resistance in Penicillin-Binding Proteins. In: T. Dougherty, M. Pucci, ed. 2012. Antibiotic Discovery and Development. New York: Springer Science+Business Media. Ch.11.

Ontario Medical Association, 2013. When Antibiotics Stop Working: Policy Paper. [online] Toronto: Canadian Electronic Library/desLibris. Available at: <http://www.deslibris.ca/ID/237015>

Wainwright, M., 1987. The History of the Therapeutic Use of Crude Penicillin.  Medical History.  31, pp. 41-50. Available at: <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1139683/pdf/medhist00068-0045.pdf>

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