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.