Junior Science

Micro-organisms and Human Health

Lesson Objectives

Understand the terms microbiology and micro-

organism

Identify the different types of Microorganisms.

Describe the characteristics of bacteria

Explain how bacteria reproduce

Discuss the importance of bacteria in the

environment

Give examples of disease causing bacteria

List the benefits and negative effects of Bacteria

Explain what is meant by the term Antibiotic.

The Nature of Micro Organisms

The study of micro-organisms is called Microbiology.

Micro-organisms also known as ‘microbes’ are small living things.

Micro-organisms consist of Organisms which survive on their own –

Bacteria. Organisms which live off other organisms

such as Viruses, Fungi and parasites

Bacteria

Bacteria are an ancient form of life.

They can live almost anywhere and are found in air, soil and in the bodies of humans and animals alike.

Most bacteria are SAPROPHYTES and live off dead matter.

Bacteria which cause disease are called ‘Germs’.

There are far more Useful than harmful bacteria.

Bacteria Structure

Bacteria are very simple organisms with no nucleus

A rigid cell wall and a thin

rubbery cell membrane.

Genetic material (DNA) is in a

structure called a chromosome which

is free to move about the cell

Threadlike structures

called flagella and Pili are

used to help them move.

Ribosomes are organelles which

are tools necessary for copying

DNA so the bacteria can

reproduce.

Plasmid is small

DNA molecules

which can replicate

on its own

Types of BacteriaBacteria are found in a number of different forms

Circular - Cocci Rod like - Bacilli spiral - Spirillum

Staphylocccus aureus Lactobacillus Borrelia

(found on the skin) (found in yoghurt) (found in ticks)

Bacteria Reproduction Under Ideal conditions bacteria

can reproduce rapidly.

In order to grow bacteria need:

Food

Water

A suitable temperature

A suitable pH

Binary Fission Reproduction During binary fission the bacteria cell divides in two

and the number of bacteria will double with each

generation

N

Calculating Bacterial Growth

We use the function y = 2n

y = Number of Bacteria

n = Number of Generations

0 1 2 3 4 5

How many bacteria in the 5th generation?

y = 2n => 25 = 2x2x2x2x2 = 32

Most bacteria can divide every 20 minutes!

Bacteria Role in the Environment

Decomposers break

down dead matter

releasing nutrients

Nitrogen fixing bacteria

convert nitrogen gas

into nitrates essential

for healthy plant growth

Some bacteria can photosynsthesis

taking CO2 from the atmosphere

Beneficial Bacteria

Ripen and Flavour Cheese

Produce alcohol and vinegar

helping to make yoghurt

Help break down grass

into Silage which is use to

feed cattle

Help decompose dead

animals and plants

releasing nutrients into the

soil.

Used in the manufacture of

antibiotics.

Harmful Bacteria

Cause food spoilage turns milk sour

Cause tooth decay as they

feed on sugar on teeth

Cause crop disease i.e. Blight

Cause disease and illness

Diseases Caused By BacteriaBubonic Plague

Typhoid Fever

Food Poisoning

Cholera

Bubonic Plague

Typhoid Fever

Food Poisoning

Cholera

Antibiotics Antibiotics are chemicals made by bacteria and

fungi which kill or prevent the reproduction of

other bacteria.

Streptomycin is made

by bacteria

Penicillin is made by a

fungus.

Summary Bacteria are an ancient form of life and importat

for life on earth

Bacteria need food, water and a suitable

temperature and pH to reproduce

Bacteria reproduce using Binary fission and the

number of bacteria can calculated using y=2n

Bacteria have an important role in the

environment as decomposers.

Bacteria are both useful and harmful

Antibiotics are chemicals made by bacteria and

fungi which kill or prevent the reproduction of

other bacteria.