Activity-based science learning: How teachers can offer students an experience of the scientific process

Rohini Karandikar and Subhojit Sen, in i wonder… magazine, delve into an activity-based approach around Alexander Fleming’s discovery of penicillin to explain how connecting experimental ideas with stories of discovery can offer students an introduction to the nature of science. 

Did you know that Alexander Fleming was not the only researcher involved in the Nobel Prize-winning discovery of penicillin? Or that it took 13 years for penicillin to be of use for humans? We present an interactive resource to unearth unsung surprises in the process of discovery of penicillin.

School textbooks devote limited space to the history of science’, often reducing it to dates, names of scientists, a couple of photographs and a few lines. Students miss out on the exciting process of science’ and the eureka moments that led to those discoveries. 

Connecting experimental ideas with stories of discovery can offer students an introduction to the nature of science. 

Not only do students discover how to develop and test a hypothesis, they learn to appreciate the importance of careful observation, patience, and collaborative work in translating discoveries in the lab into applications in the real world. 

These connections also offer students the opportunity to recognise the time, effort, and rigour involved in serendipitous discoveries.

We explore one such activity-based approach around Alexander Fleming’s discovery of penicillin (see Box 1).

Box 1. Curricular links:

This resource is suitable for grade IX and above. It is linked to:

  1. 1. Chapter 2 in NCERT’s Grade VIII textbook — Microorganisms: Friend and Foe
  1. 2. Chapter 13 of NCERT’s Grade IX textbook — Why do we fall ill?

Based on the Vigyan Pratibha learning unit — The Accidental Discovery’, this approach connects an experiment (Activity Sheet I) with an interactive story (Activity Sheet II).

Activity I: Become a microbiologist!

Encourage students to engage with this activity after they have been introduced to the idea that not all microorganisms are harmful. Lactobacilli in curd and yeast in bread can be offered as common examples of microorganisms that are, in fact, beneficial to humans.

Can we demonstrate the presence of microbes in curd without the aid of a microscope? Surprisingly, one doesn’t need to be a trained microbiologist to do this. This activity (see Activity Sheet I) allows students to grow microbes from curd (~bacterial inoculum/​seed) on a cooked potato-slice (~solid substrate), thereby avoiding difficult techniques of classical microbiology (sterilization, media preparation, specific apparatus, and aseptic conditions).

To do this, some curd is evenly spread out on a cooked potato slice, and incubated for 24 – 48 h. By the end of this period, students can see many small whitish dots on the slice — each of which is a Lactobacillus colony (see Fig. 1a).

Fig. 1. Effect of Chloramphenicol (Cam) on potato slices spread with curd. Plates with — (a) curd control, (b) 20 mg Cam, © 50 mg Cam, and (d) antibiotic control (20 mg Cam). Fewer colonies are observed around the wells in the slices with 20 and 50 mg Cam Clearance is seen on one side of the well in the slice with 20 mg Cam, and around the well for slice with 50 mg Cam. This clear zone indicates the inhibition of lactobacilli by the antibiotic, which diffuses into the slice along a concentration gradient (with the highest concentration at the center).

Credits: Manohar Dange. 

License: CC-BY-NC

Each colony consists of several million bacteria growing in a single pile that is visible to the naked eye. Students may also observe that the colonies are quite diverse in terms of their size (smaller, bigger), appearance (some translucent, others opaque) and so on.

To observe the effects of antibiotics on microorganisms, some of the potato at the center of each slice is scooped out to create a small, shallow well. Antibiotic solutions of different concentrations are added to different wells. 

Potato slices with only curd or only antibiotic can serve as parallel controls. By the end of the incubation period, students will be able to observe the presence of a clear zone of inhibition around a potato well with antibiotic solution. In other words, bacterial colonies will be fewer in number or absent from this zone (see Fig. 1b).

Box 2. Extended activity:

Students can also use this experiment to check —

  1. The presence of microorganisms in soil — by seeding the potato slices with a soil sample instead of curd, or 
  2. Differences in the nature of microbial inhibition — by using different sets of antibiotics.

It will also help solidify the idea of what Fleming is likely to have observed around the fungal colony that produced penicillin.

Activity II: Retracing the accidental discovery of penicillin

This interactive story-based activity (see Activity Sheet II) describes the discovery of modern penicillin through questions that encourage critical thinking’.

The story introduces students to the process of science, while the questions offer avenues for open thought and discussion. To ensure maximum participation by students, we highly recommend that teachers:

  • Avoid offering direct answers, and encourage discussion instead.
  • Consider all student responses without classifying them as right or wrong. Many questions need not have one right answer, and not being too critical or disapproving of students’ views will encourage open thinking.
  • List all student responses/​ideas on the board and moderate a student debate around them. This will allow students to engage with each idea, and reflect on their reasons for agreement/​disagreement.

Discussion around this activity can take many directions (see Box 3).

Box 3. Teacher’s box:

  1. Teachers may need to introduce the idea that mould are fungi whose spores are ubiquitously present in the air around us. Most saprophytic fungi grow at moderate room temperatures (e.g., mushrooms at 25°C), while disease causing bacteria tend to grow better at 37°C (human body temperature).
  2. A debate around who should’ve received the Nobel Prize for the discovery of penicillin can be an interesting exercise for students. Although the prize was
    awarded to Alexander Fleming, Howard Florey, and Ernst Chain, students may suggest that Heatley and the Penicillin girls’ were deserving, yet unsung, heroes in this process.
  3. The world wars reduced funds for research, forcing many scientists to limit their resources. But scientists involved in the discovery of penicillin were driven by the need to produce enough antibiotic to save soldiers wounded in war.
    Students may, therefore, conclude that in a way, the war pushed efforts to produce penicillin in larger amounts. This discussion is likely to help students explore the impact that politics can have on scientific discoveries.
  4. Teachers may need to provide clarity regarding the role of antibiotics. Penicillin doesn’t heal wounds. During an infection, bacteria multiply to very large numbers, which overwhelms the immune system.
    Penicillin slows down bacterial growth, indirectly giving the body’s immune system a better chance at fighting the infection.

Consider one question in the activity — what in the bread mould helps wounds heal?

Student discussion around this question can be followed up with another question — is it possible that the mould on bread releases some chemicals that could kill or inhibit the growth of bacteria in wounds? 

Once students have explored this possibility, teachers could present the fact that bread acts as a nutrient medium for all kinds of moulds to grow. 

Even if ancient Egyptians knew of ways’ to help a wound heal better, they would have less control over what kind of moulds grew on bread. 

What if some of the fungi or mould on the bread piece used for healing were non-beneficial or even toxic? 

Discussion around this part of the activity can help students differentiate between antiseptics used in traditional medicine from antibiotics in modern medicine. 

This could be used as an example of how the identification of the active component involved in the Egyptian healing technique by modern scientific principles allows us to minimise mishaps from use of ineffective or toxic moulds. 

It could also be used to illustrate how large-scale production and purification technologies have made penicillin available for use at the most effective clinical dose.

Before winding up, teachers could use some of the themes provided in parentheses to encourage students to think about the following open-ended questions:

  • What new things did you learn from this exercise? (Themes: effect of chance, accidental discoveries, collaborations, working in teams).
  • How is learning about the history of antibiotics’ significant now? (Themes: drug discoveries today also have to go through similar time- consuming and rigorous procedures of animal and clinical trials before their benefits can reach patients).
  • Bacteria and fungi have existed throughout human history. What was it that triggered the discovery of penicillin in 1928? (Theme: the accidental observation of bacteria and fungi growing on the same plate, uncovering their antagonism).
  • If there were so many scientists and assistants involved in the discovery of penicillin, why is only Fleming’s name popularly associated with it? (Theme: primary discoverer).

Parting thoughts

Students are never really offered an experience of the scientific process. How do ideas nucleate from observations of the natural world? How do we use the scientific principle of controls and rational thinking to find scientific explanations for observed phenomena? 

These activities aim to offer students this experience by engaging with both narrative and experimental evidence. 

They also provide an introduction to the world of microbes; helping students appreciate how some microbes are useful, while others are harmful. 

Finally, it helps students understand that the fruition of any idea in science involves many people, although only a fortunate few get recognised or awarded the Nobel Prize for their contributions.

Key Takeaways

  • Re-tracing Fleming’s chance discovery of penicillin will offer students an appreciation for the importance of keen observation in science, and the role it plays in serendipitous discoveries.
  • An understanding of the struggle to generate penicillin in amounts required for human use will help students appreciate that a chance observation is only the beginning of a complex (scientific) process that demands time, patience, and rigour.
  • Recognising the contributions of Howard Florey, Ernst Chain, Norman Heatley, and the Penicillin girls’ in bringing penicillin from the bench to the bedside will help introduce students to the highly collaborative nature of modern science.
  • Reflection on the role of war, and the unsung contributions of many people involved in the story of penicillin will offer students a better understanding of the political and human dimensions of science.
  • By actually growing microorganisms in the presence of antibiotics, students will be able to appreciate Fleming’s initial observation and learn a new way to query the world of microbes around them using simple kitchen equipment.


The authors would like to thank Leena Phadke, Associate Professor (Retd.) Ramnarain Ruia College, Mumbai, for her ideas on the potato slice experiment, and development of the narrative on the discovery of penicillin. 

We acknowledge the support of the Govt. of India, Department of Atomic Energy, under the Vigyan Pratibha Project (No. R&D‑TFR-0650).

We also thank the DBT Ramalingaswami Fellowship, all the students who were part of the field trials for these activities, and all Vigyan Pratibha members for providing their inputs during the development of these activities.


  1. This article is based on the learning unit The Accidental Discovery’ from the Vigyan Pratibha project (https://​vigyan​prat​i​b​ha​.in/​i​n​d​e​x​.​p​h​p​/​t​h​e​-​a​c​c​i​d​e​n​t​a​l​-​d​i​s​c​o​very/), currently undertaken by the Homi Bhabha Centre for Science Education, TIFR, Mumbai.
    Vigyan Pratibha is a central government initiative for students of grades VIII‑X of Kendriya Vidyalayas, Jawahar Navodaya Vidyalayas, and Atomic Energy Central Schools. This science nurture programme aims to develop critical thinking skills among students of diverse backgrounds by engaging them in an activity-based approach to learning school science and mathematics.


  1. Douglas Allchin (2002) Scientific Myth-Conceptions, Fourth International Seminar on the History of Science and Science Education: Issues and Trends, Stephen Norris (Section Ed.) URL: http://​dou​glasallchin​.net/​p​a​p​e​r​s​/​m​y​t​h.pdf
  2. Alexander Fleming biography: https://​www​.biog​ra​phy​.com/​p​e​o​p​l​e​/​a​l​e​x​a​n​d​e​r​-​f​l​eming. Last updated: Jun 262019.
  3. Discovery and Development of Penicillin. International Historic Chemical Landmark. URL: https://​www​.acs​.org/​c​o​n​t​e​n​t​/​a​c​s​/​e​n​/​e​d​u​c​a​t​i​o​n​/​w​h​a​t​i​s​c​h​e​m​i​s​t​r​y​.html
  4. Howard Markel. The Real Story Behind Penicillin. PBS Newshour. URL: https://​www​.pbs​.org/​n​e​w​s​h​o​u​r​/​h​e​a​l​t​h​/​t​h​e​-​r​e​a​l​-​s​t​o​r​y​-​b​e​h​i​n​d​-​t​h​e​-​w​o​r​l​d​s​-​f​i​r​s​t​-​a​n​t​i​b​iotic
  5. Alexander Fleming (1929). On the bacterial action of a culture of Penicillium with special reference to their use in the isolation of B. influenzae. British Journal of Experimental Pathology, 10(3): 226 – 236.
  6. Kelly Swain (2017). The Penicillin girls (and guys). The Lancet, Vol 389, pp.1507.

About the authors:

Rohini Karandikar was formerly a postdoctoral fellow at the Homi Bhabha Centre for Science Education (HBCSE), TIFR, Mumbai, India. She now works as a curriculum and innovation manager at Curiosity Gym, Mumbai. Rohini can be contacted at rohinimd25@​gmail.​com

Subhojit Sen is a DBT Ramalingaswami Fellow at the School of Biological Sciences, UM-DAE Centre for Excellence in Basic Sciences, Mumbai University (Kalina Campus), Mumbai, India. He can be contacted at subhojit.​sen@​cbs.​ac.​in

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