Recreating Alexander Fleming's Discovery of Penicillin

We live in a world where so many medical discoveries are taken for granted. A prime example of this is the discovery of Penicillin by Alexander Fleming (1881 - 1955) in 1928. While it might seem preposterous that someone could die from a common flu today, this was seen in the 1918 pandemic where the U.S. saw a staggering 583 deaths per 100,000 people from influenza and pneumonia. Additionally, the graph provided even depicts the rapid decrease in syphilis cases all over the world. Thus, we can all agree that penicillin has had a massive impact on our lives.

This black and white picture taken is best known for being the original contaminated culture that led to his discovery of Penicillin. The mould growing towards the top of this Petri dish is best known as penicillium rubrum. Fleming noticed that the mould (Penicillium rubrum) that had entered his petri dish had killed the surrounding Staphylococcus bacteria. He observed a clear zone around the mould where bacteria could not grow, realising the fungus produced a substance that had antibacterial properties.

When he further explored the capabilities of Penicillium rubrum, he discovered that it could fight the Streptococcus species as well. This included Streptococcus pyogenes (the cause of strep throat and scarlet fever), Streptococcus pneumoniae (a cause of bacterial pneumonia and meningitis) and other species as well.

Since this experiment is about recreating Fleming's experiment, this requires recreating the conditions of his penicillin culture plate. For this experiment you will need:

1. Agar Plates (At least 3)
2. Yogurt (I chose homemade)
3. A slice of bread with visible penicillium mould on it (It must look like the picture provided)
4. Sterile swabs
5. A pair of gloves
6. A marker

To begin this experiment, choose an environment to grow your fungus that is away from direct sunlight and moisture. I chose a dark cupboard to maintain a consistent growth of the fungus and minimise contamination during the experiment.

To further ensure that my results were accurate, I also sterilised the cupboard surfaces using an antibacterial sanitiser. This prevents any external interference in the span of the experiment.

The second and arguably largest step in this experiment is preparing the agar plates before introducing the fungus. In this step, it is imperative to check your agar plates for any prior contamination of any kind (This includes cracks or condensation on the roof of the plate).

After this process, label each one of your plates either as a control, a test, or a replicate copy. The purpose and contents of each of these plates are listed as follows:

1. Control Plate (Second furthest from right): This should be only the bacterial sample (a thin layer of the yoghurt) on the agar plate. It is to compare how normal bacteria grows without any mould. It is a basis for comparison with other plates. Label this 'Control'

1. Test Plate (Second from the left): Contains the bacterial sample and a small piece of mouldy bread. This is to observe whether the fungus inhibits bacteria growth, as Fleming's experiment showed us. Label this 'A'

1. Replicate Plate (Furthest to the left): Contains the same bacterial sample as its test plate, including the mouldy piece of bread. It is a near replica of the original plate but with the intent of ensuring the first attempt's results weren't a 'fluke'. Label this 'A+'

The following were the conclusions I was able to derive based on the results of the agar plates:

1. Control Plate: The agar had a cloudy and somewhat even layer of bacterial growth across the surface, with no mould present. This demonstrated how the bacteria would normally grow without fungal interference.

1. Test Plate: The mould began growing outward from the piece of mouldy bread and there is a light ring (known as the zone of inhibition) around the mould which shows that the fungus was preventing bacterial growth in this area.

1. Replicate Plate: The plate showed similar results to the test plate, with mould growth surrounded by an area of reduced bacterial growth. This confirmed that my observations in the test plate were reproducible and with limited experimental error

The outcomes of this experiment show similar results to what Fleming’s original experiment had. The white ring around the penicillium rubrum clearly shows that the fungus secretes a type of acid that killed most or even all of the Staphylococcus bacteria.

This experiment teaches us humans that mistakes, in fact, can still result in positive outcomes based on the way interpreted. 98 years ago, a man named Alexander Fleming revolutionised the medical field by discovering something that he at first, never thought was useful. Yet it was this accidental discovery that has saved nearly 500 million lives all around the world today.

FUN FACT: Until recently, all the penicillin produced in the USA and Britain were all sub-cultures of the Fleming’s original mould colony from 1928.

Ending on this note:

When life gives you mold, make antibiotics!