THE INDIAN COMMUNITY SCHOOL,

KUWAIT

Study of Effects of
Antibiotics on
Microorganisms
By Dhyan Niranjan Harikumar
Class: XII-A
Admno. No: 124005
 BONAFIDE CERTIFICATE

This is to certify that …………………………….…….is a Bonafide student of ICSK Kuwait

(Khaitan/Senior).

He/she is currently enrolled in Class …………………Section …………, with the admission

number ………………………….

His/her father's name is ………………………….and mother's name is

……………………………...

This certificate is issued for the purpose of the project viva in accordance with the CBSE
Biology Viva Project norms and guidelines.

Authorised Signatory

Date:

School Seal

ACKNOWLEDGEMENT
I would like to extend my sincere and heartfelt gratitude to everyone who assisted me in
completing this project. Without their active guidance, help, cooperation, and
encouragement, I would not have been able to present this project on time.

I am extremely thankful and sincerely grateful to my biology teacher,

…………………………... for his/her valuable guidance and support in the completion of
this project.

I also express my deep sense of reverence and gratitude towards our Principal, Vice
Principal, the entire Department of Biology, as well as my parents, friends, and well-wishers
for their valuable suggestions and unwavering support throughout this process.

Date:

Place:

CERTIFICATE OF COMPLETION
This is to certify that the project work on ………………………………. based on the CBSE
curriculum has been successfully completed by ………………………of Class XII, Section
…………. of ICSK Kuwait.

The aforementioned project has been completed under my guidance during the
academic year 2025-26

…………………………

Signature of the Teacher

SELF-CERTIFICATION OF AUTHENTICITY

I, …………………, a student of Class XII, Section ……………... of ICSK

Kuwait, hereby certify that the project work on ……………….is my

original work. I affirm that I have not used any AI tools or engaged in plagiarism in the
completion of this project. All research and content included in the project are authentic
and my own work.

I understand and agree that if any part of this project is found to be plagiarized, the teacher,
in consultation with the Head of the Department, Vice Principal, or/and Principal, has the
authority to reject the project and award me zero marks.

Index

1. Introduction.

2. Theory
a) Types of Microorganisms.
b) Commonly used Antibiotics.
c) Mechanism of Action of Antibiotics.
d) Antibiotic Resistance- Causes and Consequences.

3. Experiment
a) Aim.
b) Materials required.
c) Procedure.
d) Observations.
e) Inference.
f) Precautions.
g) Results and findings.
h) Conclusion.

4. Bibliography.
1) Introduction

Antibiotics are strong chemical substances that kill bacteria and some other
tiny organisms or stop them from growing. Some are made by fungi or bacteria,
but others are created in labs.

In 1928, Alexander Fleming's discovery of Penicillin changed medicine. It gave

doctors a way to fight deadly bacterial infections. Antibiotics stop bacteria by
inhibiting important functions like how they build cell walls, make proteins, or
copy DNA. This either kills the bacteria or keeps them from growing. But
antibiotics do not work on viruses, like the ones that cause colds or the flu.

Now, we use antibiotics a lot to treat infections like pneumonia, tuberculosis,

urinary tract infections, and skin infections. Even though they're helpful, using
them too much has caused antibiotic resistance. This is when bacteria become
resistant to the drugs, which makes infections harder to treat and is a big worry
for everyone's health.
2. Theory

a) Types of Microorganisms
Bacteria are single-celled organisms that lack a nucleus. They exist in numerous
environments such as soil, water, and within humans. Certain bacteria assist
with digestion and the recycling of nutrients, while others result in diseases like
tuberculosis and strep throat. They quickly reproduce through binary fission.

Fungi consist of yeasts and molds, which are complex cells with nuclei and
chitin cell walls. Fungi break down dead material, recycling nutrients in
ecosystems. Some fungi assist in the production of bread and alcohol, but
others produce infections such as ringworm and athlete's foot.

Viruses are minute microorganisms that can only replicate inside living cells.
They cause diseases such as flu and the common cold. Viruses consist of
genetic material covered by a protein coat and are not living organisms
because they cannot reproduce on their own.

Protozoa and Algae are single-cell microorganisms. Protozoa are usually aquatic
and, at times, give rise to diseases such as malaria. Algae are autotrophic and
carry out photosynthesis, releasing oxygen and also serving as the foundation
of most aquatic food chains.

b) Commonly Used Antibiotics

Antibiotics are medications that are utilized in the treatment of bacterial
infections by either killing bacteria or inhibiting their growth. Antibiotics vary in
how they kill bacteria, and physicians select them depending on the type of
infection and bacteria. Some of the popular antibiotics are Penicillin,
Tetracycline, Amoxicillin, Ciprofloxacin, and Erythromycin.

The initial widely used antibiotic was penicillin, discovered in 1928 by

Alexander Fleming. Penicillin works by preventing the formation of bacterial
cell walls, causing the bacteria to burst and die. Penicillin treats a broad
spectrum of bacteria and is often used to treat illnesses like strep throat,
pneumonia, and skin infections.

Tetracycline is a broad-spectrum antibiotic that inhibits the synthesis of

proteins in bacteria, thereby stopping bacterial growth and multiplication.
Tetracycline is used to treat respiratory tract infections, urinary tract infections,
acne, and certain sexually transmitted infections. It should not, however, be
given to pregnant females and young children due to side effects.

Amoxicillin is a penicillin-like antibiotic with an extended spectrum of activity. It

is used for the treatment of infections such as ear infections, bronchitis, and
urinary tract infections.
Amoxicillin is frequently paired with clavulanic acid to combat bacterial
resistance due to enzymes that degrade antibiotics.

Ciprofloxacin is a fluoroquinolone that functions by blocking bacterial DNA

replication. Ciprofloxacin is employed to cure some serious infections, such as
urinary tract infections, gastrointestinal infections, and pneumonia.
Ciprofloxacin should be used carefully due to the risk of side effects, including
tendon problems.

Erythromycin is a macrolide antibiotic that inhibits bacterial protein synthesis.

It is used frequently in patients allergic to penicillin and is utilized in the
treatment of respiratory infections, skin infections, and whooping cough.

Each antibiotic has its own uses, benefits, and limitations. Antibiotics should
only be used when recommended by a health care provider to avoid antibiotic
resistance, a growing global health problem.

c) Mechanism of Action of Antibiotics

Antibiotics produce their actions by way of acting upon certain structures or
processes of bacterial cells, thereby killing the bacteria or suppressing their
growth and multiplication. Different mechanisms of action are known for
antibiotics, depending on their chemical nature and their site of action.

One main mechanism is the inhibition of bacterial wall synthesis. Penicillin and
Amoxicillin are examples of antibiotics that somehow inhibit bacteria from
synthesizing cell walls, which are very potent for the formation and the
protection of bacteria. The bacteria rupture and die with osmotic pressure in
the absence of a functional cell wall. This mechanism acts only on bacteria that
are actively growing.

Another mechanism is protein synthesis inhibition. Tetracycline and

Erythromycin antibiotics bind to bacterial ribosomes, which are the protein
synthesis site. They prevent bacterial cells from synthesizing proteins required
for their own growth and survival, leading to their death or halting their
reproduction.

Some antibiotics, such as Ciprofloxacin, work by interfering with nucleic acid

synthesis. While many antibiotics treat bacterial infections, Ciprofloxacin
interferes with bacterial enzymes needed to replicate DNA or repair DNA,
specifically DNA gyrase and topoisomerase IV. Since these bacteria cannot
create functional DNA because of troubled DNA replication, by blocking or
inhibiting these enzymes, the bacteria cannot replicate and die.
Some antibiotics may affect the cell membrane. Some antibiotics such as
Polymyxins will penetrate the bacterial cell membrane and cause it to become
permeable that kills the cell by enabling cell contents to leak out. We used
antibiotics like this sparingly because of the toxic effects they have on human
cells.

Another mechanism is antimetabolite action and this antibiotic action takes

place in some antibiotics like Sulphonamides that stop bacteria from making
folic acid. Folic acid is necessary for protein and DNA synthesis. Without folic
acid, bacteria cannot grow.

As a whole, antibiotics are meant to target bacteria cells and not human cells.
Thus, these are the best types of treatments for infections. But if misused they
can be resistant and will it lose its effectiveness.

d) Antibiotic Resistance – Causes and Consequences

Antibiotic resistance happens when bacteria change in ways that decrease or
destroy the effectiveness of antibiotics. Antibiotics are medications that kill
bacteria or inhibit their growth. Therefore, bacteria continue to survive even in
the presence of drugs that normally kill or inhibit that bacteria, which makes
certain infections more difficult to treat.

(i) Causes of Antibiotic Resistance:

1. Antibiotic Overuse and Misuse: Clinical practice suggests the use of

antibiotics without a prescription, not finishing the full course, or even using
them when there is a viral infection like a cold all lead to bacteria changing
their patterns of growth so they can survive.

2. Inappropriate Prescribing: Several times, doctors may prescribe antibiotics

when it is not appropriate or prescribe the incorrect dose or type of antibiotic.

3. Use in Animal Agriculture: Antibiotics are commonly used in farming to

increase animal growth and prevent illness/disease, which promotes resistant
bacteria development and consequently spread to humans.

4. Inappropriate Infection Control: In hospitals and clinics, resistant bacteria

can spread from person to person, due to a lack of proper infection control and
limited sterilization procedures.

5. Resistance through Gene transfer and mutations: Bacteria can adapt

naturally because they can contain one or more mutations within their species.
Bacteria are also able to transfer their resistance through processes of
conjugation, transformation, and transduction among themselves and all
species in very rapid succession.

(ii) Consequences of Antibiotic Resistance:

1. Treatment Failure: Standard antibiotics may not work in resistant infections,

requiring stronger, more expensive, or more toxic medications.

2. Increased Mortality and Morbidity: Resistant infections may cause longer

length of illness, complications, and death rates.

3. Threat to Medical Advances: Medical advances that are due to antibiotic

improvements such as surgeries, cancer therapies, or solid organ transplants
are threatened as antibiotic resistance jeopardizes good outcomes of
antibiotics.

4. Global Threat: Antibiotic-resistant bacteria can easily transit across borders

around the world by air travel and trade, making it a major public health
threat.
3) Experiment: Testing Antibiotics on Yogurt Bacteria

a) Aim:
To study the effect of antibiotics on bacterial growth from yogurt.

b) Materials Required:
(i) Plain yogurt.
(ii) Warm water.
(iii) Sterile cotton buds or earbuds.
(iv) Two clean transparent glass cups.
(v) Antibiotic tablet (Amoxicillin).
(vi) Spoon to crush tablet.
(vii) Cling film or plastic wrap or plate to cover jars.
(viii) Labels and marker.

c) Procedure:
(i) Label jars as Standard and Antibiotic.
(ii) Pour equal amounts of warm water in both cups
(iii) Add 1 teaspoon of yogurt into each jar and stir gently with clean spoon.
(iv) Crush half a tablet of antibiotic and add it to the cup labelled Antibiotic. Stir
well.
(v) Cover both jars with cling film or plates.
(vi) Leave them undisturbed in a warm place for 8-12 hours.
(vii) Observe differences in smell, texture or curdling between the two cups.

d) Observations:
(i) The Standard cup should form yogurt normally.
(ii) The Antibiotic cup may show less curdling or watery mixture, indicating
inhibited bacterial growth.

e) Inference:

Antibiotics prevent bacterial growth, as shown by the reduced curdling in the

antibiotic-treated sample.

f) Precautions:
(i) Do not use harmful bacteria.
(ii) Dispose of them safely in a plastic bag.
(iii) Do not taste the samples after the experiment.
(iv) Use harmless sources like yogurt (contains Lactobacillus) or curd water for
bacterial growth.
g) Results and Findings
h) Conclusion

This project provided a comprehensive understanding of antibiotics, the

different types of antibiotics, mechanism of action, and their significance in
treating bacterial infections that were once considered fatal.

The simple experiment using yogurt bacteria affirmed that antibiotics can
inhibit bacterial growth which corresponds to their uses in medicine. The
findings also addressed the issue of antibiotic resistance that is thought to
increase because of many factors including inappropriate prescriptions, self-
prescribing, not completing the prescriptions, same-day dispensers, and
indiscriminately utilizing antibiotics in agriculture which is analysed as a
potential threat. This little increase of one strain of bacteria creates a bigger
challenge that makes the treatment of common infections problematic for a
patient and creates a further risk for death or complications if it is untreated.

This means we have to use antibiotics when needed, and prescribed by a

licensed doctor, and complete the full course without stopping. There is also an
urgent matter in continued research for new antibiotics, bacteriophage
treatments, and better diagnostics to limit treatment against resistant strains of
bacteria.

So, it is crucial that in the meantime we research ways to use antibiotics

smarter and to continue to address more studies and promoting programs to
raise awareness of antibiotic use to dramatically decrease resistance to
antibiotics so that these lifesaving medicines remain usable by the next
generation.
4) Bibliography

a) NCERT Biology Class XII Textbook – Chapter: Microbes in Human Welfare.

b) Tortora, Funke, and Case – Microbiology: An Introduction (Pearson

Education).

c) World Health Organization (WHO) – Antibiotic Resistance.

https://www.who.int/news-room/fact-sheets/detail/antibiotic-resistance

d) Centres for Disease Control and Prevention (CDC) – About Antibiotic

Resistance.

https://www.cdc.gov/drugresistance/about.html

e) Fleming, A. (1929). On the Antibacterial Action of Cultures of a Penicillium.

British Journal of Experimental Pathology.

f) Indian Council of Medical Research (ICMR) – Guidelines on Antimicrobial

Use.

g) S. Chand – Principles of Biology for Class XII.

h) Practical experiment references from school lab manual.