Micro-organisms include bacteria, viruses, and fungi. They are single-celled organisms that are too small to see with the naked eye. Bacteria can be helpful or harmful, and have different shapes. Viruses are even smaller than bacteria and can only reproduce inside other cells. Fungi are the largest microbes and absorb nutrients from their surroundings. The three main groups of microbes differ in their structures, reproduction mechanisms, and impacts on other organisms.

1. What are micro-organisms?

2. Microbes
– Microbes are single celled organisms
– Too small to be seen with the naked eye
– They are found practically EVERYWHERE on earth
– Also commonly known as bugs, germs and microbes
– Generally divided into 3 different groups
• Bacteria
• Virus
• Fungi

3. Bacteria
– Obtain nutrients from their environments in order to live. In some cases that
environment is a human body
– Most are helpful or harmless. But some cause disease
– Bacteria can reproduce outside of the body or within the body as they cause
infections
– Some bacteria are good for our bodies:
• Good bacteria live in our intestines and help us use the nutrients in the food we
eat and make waste from what's left over.
– They are found everywhere on earth, in the ocean, in rocks, in volcanoes, in
our bodies and in the soil

4. Bacterial Structure
Chromosome: DNA material of the cell
Cell wall: Composed of peptidoglycan the cell wall maintains the
overall shape of a bacterial cell
Cell membrane: Lining the inside of the cell wall it provides a boundary for
the contents of the cell and a barrier to substances entering
and leaving.
Cytoplasm: Describes the inside of the cell and the contents
Chromosome
Cell Membrane
Cytoplasm
Cell wall

5. Bacterial Shapes
There are 3 different shapes of bacteria
Spirals
(Campylobacter)
Rods
(Lactobacillus)
Balls or cocci
(Staphylococcus)

6. Viruses
– Viruses are even smaller than bacteria and can sometimes live INSIDE
bacteria
– Most viruses make us ill
– Diseases like CHICKENPOX and the FLU are caused by viruses.
– Viruses are easily spread from one person to another.
– Viruses cannot reproduce by themselves. They infect other cells and take
over their reproductive machinery in order to reproduce.
– They multiply inside the ‘host’ cell and when they have used all the cells
reproductive machinery, thousands viral cells burst out of the cell. The host
cell is completely destroyed.

7. Viral Structure
Envelope
• Double lipid layer holding the cells
genetic material.
Glycoproteins
These serve 2 purposes
• Anchor the virus to the host cell.
• Transport genetic material from the
virus to the host cell.
Nucleic acid
• Either DNA or RNA material, but
virus cells rarely contain both. Most
viral cells contain RNA material.
Complex
(Bacteriophage – a virus
which infects bacteria)
Envelope
Nucleic acid
Glycoproteins

8. Viral Shapes
Icosahedral
(Influenza)
Complex
(Bacteriophage – a virus which infects
bacteria)
Helical
(Tobacco mosaic virus)
Thereare3 differentshapesofVirus

9. Fungi
– The largest and most versatile of all microbes
– Large plant like structures which lack chlorophyll
– Need to absorb nutrients from whatever they are growing on
– Fungi can be very helpful and humans have used them in
– The food industry - brewing beer, making bread rise
– Medicine – making antibiotics
– They can also be harmful if they steal nutrients from another living
organism. Examples include, mould on bread and athletes foot
which is caused by a group of fungi known as dermatophytes
– Fungi can be found in the air, on plants and in water

10. Fungal Structure
Sporangia:
Spore producing body.
Sporangiophore:
Filamentous stalk on which the sporangium forms.
Rhizoids:
The sub-surface hyphae are specialized for food absorption.
Sporangiophore
Sporangia
Rhizoids