This is a lesson on types of microbes, according to objectives from the Caribbean Secondary Education Certificate (CSEC) Syllabus for Integrated Science. It focuses on the three main types of microbes - viruses, bacteria and fungi, comparison of their sizes as well as structure and function. I teach online exclusively, and this is one of the slide decks that I use for my live session and/or recorded lectures.

1. Syllabus Section A: The Organism & its Environment
Unit I: Matter
TYPES OF MICROBES
KEISHA S LEWIS | ‘THE BIOSPECIALIST’ © CC 2020

2. OBJECTIVES SYLLABUS OBJECTIVE(S)
Candidate should be able to:
● Discuss the importance of selected microbes;
LESSON OBJECTIVE(S)
By the end of this lesson, the student should be able to:
Distinguish between the different types of microbes - viruses,
bacteria, and fungi;
Describe important characteristics of each type of microbe;
List examples of diseases caused by each type of microbe.
KEISHA S LEWIS | ‘THE BIOSPECIALIST’ © CC 2020

3. INTRODUCTION
In this lesson we will be looking at
microorganisms.
The gif is that of BACTERIA, which
is one type of microorganism (aka
microbe).
KEISHASLEWIS|‘THEBIOSPECIALIST’©CC2020

4. THINK ABOUT IT
This lesson will look at
BACTERIA (as shown in this
gif), and two other types of
microbes.
What do you think those
other types are?
Do you think they will look the
same?
KEISHASLEWIS|‘THEBIOSPECIALIST’©CC2020

5. WHAT IS A
MICROORGANISM?
Microorganisms, aka
microbes, are unicellular
organisms which are
only visible with the aid
of a microscope.
KEISHA S LEWIS | ‘THE BIOSPECIALIST’ © CC 2020

6. EXPLANATION
There are three types of
microbes:
● Viruses
● Bacteria
● Fungi
Viruses are the smallest,
fungi are the largest.
They have various shapes
and sizes.
KEISHA S LEWIS | ‘THE BIOSPECIALIST’ © CC 2020

7. VIRUSES
All are pathogens.
However, not all hosts are humans.
Therefore not all viruses are harmful to
humans.
Some can even be of benefit.
Pathogenic viruses cause diseases such
as influenza, cold sores, chicken pox,
mumps, measles and AIDS.
HEPATITIS C VIRUS
(Centre for Disease
Control)
KEISHASLEWIS|‘THEBIOSPECIALIST’©CC2020

8. VIRAL
STRUCTURE
HEPATITIS C VIRUS
(Centre for Disease
Control)
All consist of genetic
material (DNA or RNA)
enclosed in a protective
protein coat.
Size range:
20 to 400 nm
(nanometres)
[1 million nm in 1 mm).
KEISHA S LEWIS | ‘THE BIOSPECIALIST’ © CC 2020

9. HOW DO
VIRUSES
REPRODUCE?
Viral reproduction (aka viral replication) has three (3)
main stages:
1. The virus attaches itself to the host cell and injects
its genetic material into the cell
2. The genetic material then forces the cell’s
machinery to make more copies of the virus’
material (genetic material + components of the
protein coat)
3. The host cell eventually bursts to release new
viruses into its surroundings.
The following video provides more details…
KEISHASLEWIS|‘THEBIOSPECIALIST’©CC2020

10. HOW DO
VIRUSES
REPRODUCE?
KEISHA S LEWIS | ‘THE BIOSPECIALIST’ © CC 2020

11. BACTERIA
Some bacteria are harmful to our
health, and also cause food spoilage.
Pathogenic bacteria cause illnesses
such as:
● Food poisoning caused by
salmonella
● Whooping cough
● Meningitis
● Tuberculosis (TB)
● Gonorrhoea
KEISHA S LEWIS | ‘THE BIOSPECIALIST’ © CC 2020

12. BACTERIAL
STRUCTURE I
There are many types of
bacteria, with a wide
variety of shapes and
sizes.
KEISHA S LEWIS | ‘THE BIOSPECIALIST’ © CC 2020

13. BACTERIAL STRUCTURE II
Bacteria are larger than viruses but smaller than fung, as well as animal & plant cells.
Width ranges from 0.1 to 50 µm (micrometres) [1,000 µm in 1.0 mm]
KEISHASLEWIS|‘THEBIOSPECIALIST’©CC2020

14. BACTERIAL STRUCTURE III
All bacteria have a typical cell structure, with
some differences.
The most important difference is that the
genetic material is not contained in a
nucleus. Instead, it floats freely in the
cytoplasm.
Another difference is that, like a plant cell, it
has cell wall. But it also has an additional
cell capsule with a slimy consistency.
KEISHA S LEWIS | ‘THE BIOSPECIALIST’ © CC 2020

15. FUNGI
There is a wide variety in the
types of fungi that exist.
Some, like yeast, is unicellular.
Others, like mushrooms, are
multicellular and can be seen
with the naked eye.
KEISHA S LEWIS | ‘THE BIOSPECIALIST’ © CC 2020

16. HOW DO FUNGI CAUSE HARM?
Overgrowth can harm the host
organism / substrate on which
they grow.
For example:
The unpleasant and unsightly
growth of mould, athlete’s foot
or thrush
In agriculture, fungal
infestations can lead to loss of
crops and income.
KEISHASLEWIS|‘THEBIOSPECIALIST’©CC2020

17. YEAST
STRUCTURE
Yeast has the typical
structure of a plant cell,
minus the
photosynthesizing
chloroplast.
KEISHA S LEWIS | ‘THE BIOSPECIALIST’ © CC 2020

18. YEAST
REPRODUCTION
They reproduce asexually by a
process called BUDDING.
The buds eventually break away from
the parent cell to form a new yeast
cell.
KEISHA S LEWIS | ‘THE BIOSPECIALIST’ © CC 2020

19. INSUMMARY
PART1
● A microorganism is also known as a microbe.
● A microbe is an organism that can only be seen with
a microscope. It is too small to be seen with the
naked eye. It is usually unicellular, which means it is
made of one cell.
● This lesson looked at three main types of microbes:
viruses, bacteria and fungi. Viruses are the smallest
and fungi are the largest.
KEISHA S LEWIS | ‘THE BIOSPECIALIST’ © CC 2020

20. INSUMMARY
PART2
● Viruses are basically made up of a protein coat
protecting genetic material. All are pathogens, but not
all are harmful to humans. They use their host cells to
reproduce.
● Bacteria have a wide range of sizes and shapes, but
typically have a structure similar to a cell, with an
extra cell wall and cell capsule protecting it.
● Most fungi are multicellular. Yeast, however, is
unicellular, with a structure very similar to that of a
plant cell, minus the chloroplast.
● Yeast reproduces asexually via a process called
budding.
KEISHA S LEWIS | ‘THE BIOSPECIALIST’ © CC 2020

21. REFERENCES...
Centers for Disease Control & Prevention, Illustration of the Hepatitis C Virus, viewed on 16th July
2019, <https://www.cdc.gov/nchhstp/newsroom/images/2016/HCV-virus-highres.png>
CNX OpenStax, viewed on 16th July 2019,
<https://commons.wikimedia.org/wiki/File:OSC_Microbio_01_03_sizes.jpg>
Conn, H.W., 1917, Image from page 110 of “Bacteria, yeasts and molds in the home”, viewed on
16th July 2019, <https://www.flickr.com/photos/internetarchivebookimages/20772715922/>
Domdomegg (Wikimedia Commons), File: Simple diagram of bacterium (en).svg, viewed on 16th
July 2019, <https://commons.wikimedia.org/wiki/File:Simple_diagram_of_bacterium_(en).svg>
DONIYER YAKHSHIBAYE / 7, viewed on 16th July 2019, <https://pxhere.com/en/photo/1583873>
Doug Jordan, M.A, USCDCP, viewed on 16th July 2019, <https://pixnio.com/science/microscopy-
images/influenza/portion-of-the-virions-outer-protein-coat-has-been-cut-away-which-reveals-the-
virus-contents>

22. REFERENCES cont’d/…
Mariana Ruiz, File: Bacterial morphology diagram.svg, viewed on 16th July 2019,
<https://en.wikipedia.org/wiki/Bacteria#/media/File:Bacterial_morphology_diagram.svg>
NA, (gIF: bacteria moving around), viewed on 16th July 2019,
<https://media3.giphy.com/media/8lsNyZVWcpZ2o/giphy.gif?cid=e1bb72ff5d2df504677445476b283dc4&rid=g
iphy.gif>
OpenClipart-Vectors from Pixabay, (Microscope-Scientist-Image), viewed on 16th July 2019,
<https://pixabay.com/vectors/analysis-biology-cell-cell-culture-2025834/>
Public Domain, viewed on 16th July 2019, <https://pxhere.com/en/photo/171607>
Ricochet Science, 24th Nov 2014, The Viral Life Cycle, viewed on 16th July 2019,
<https://youtu.be/uIut0oVWCEg>
Tania Chung, 2017, Integrated Science for CSEC Examinations, Macmillan Education, London, viewed on 16th
July 2019
UMass Amherst Libraries, 11th May 2016, 57. Budding of Yeast Cells, viewed on 16th July 2019,
<https://youtu.be/GFEgB_ytDZY>