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INTRODUCTION TO
MICROBIOLOGY

YEAR 2
BSC HONOURS PROGRAMME

Contents
What is Microbiology?
...
3
The Evolution and Diversity of Microbial Cells
...
4-4
Microorganisms and The Environment
...
6

2|P age

What is Microbiology?
Microbiology is the study of microorganisms such as bacteria, archaea, protozoa, fungi and viruses on fundamental and
clinical aspects
...
multicellular organisms, potentially

The Importance of Microorganisms
Microbes are the oldest form of life and they account or the largest biomass on Earth
...


The Evolution and Diversity of Microbial Cells
Evolution is the process of change in genetic material over time as a result of mutation(s), genetic recombination, natural
selection, and various other pressure factors which leads to the production of new species of organisms
...

The evolution of microbes is studied by comparing and establishing genetic, evolutionary relationships between the
organisms – a process called Phylogeny
...
Phylogeny was used in the classification of the 3 domains of life:
DNA
3
...


Gene encoding
ribosomal RNA

Aligned rRNaA
gene sequences

Cells
2
...


1
...


4
...

A G C T A A G

BACTERIA

ARCHAEA

Entamoebae Slime
molds

Euryarchaeota
Methanosarcina
Mitochondrion
MethanoExtreme
GramCrenarchaeota
bacterium
halophiles
Proteobacteria positive Thermoproteus
bacteria
Thermoplasma
Pyrodictium
Chloroplast
Thermococcus
Cyanobacteria

Nitrosopumilus

Pyrolobus

1
5
...


2

EUKARYA

Green nonsulfur
bacteria

Green sulfur
bacteria

3

AGT GGG T AG 1
A T T CCG TA G 2
AGC GGT T AG 3

Macroorganisms

Animals
Fungi
Plants
Ciliates

Flagellates

Methanopyrus

Trichomonads

Thermotoga
Thermodesulfobacterium
Aquifex

Microsporidia
Diplomonads

Figure 1
...


The 3 domains of life are archaea, bacteria and eukarya
...
Research
had shown that there is more genetic relation between archaea and eukarya than archaea and bacteria
...


Mammals

Humans

Vascular
plants

Origin of Earth

Shelly
invertebrates

(4
...
2: Timeframe of life development on Earth
...
6
billion years old and the first LUCA is believed to have appeared
between 3
...
9 billion years ago (bya)
...
Earth was exclusively microbial until 1bya when divergent
evolution resulted in the creation of multicellular organisms in the
eukarya domain
...
Their DNA is
bya
typically a single, circular chromosome containing essential
genes for survival such as metabolic & reproductive genes
...
Prokaryotes are generally smaller
than eukaryotes
...
This would be associated with
DNA-binding proteins, and there is usually more than 1
Figure 1
...

The genetic material undergoes mitosis for cell multiplication and meiosis for sexual reproduction
...
Eukaryotes are generally larger and more complex than prokaryotes
...
1: Generalized characteristics of microbes
Contains…
Membrane-defined nucleus
Histones
Plasmid(s)
Simple/Complex NAPs
Operons
Peptidoglycan in the cell wall
Ester-linked lipid(s)
Multicellular organism(s)
Pathogen(s)

Archaea
No
Yes
Yes
Complex
Yes
No
No
No
No

Bacteria
No
No
Yes
Simple
Yes
Yes
Yes
No
Yes

Eukarya
Yes
Yes
No
Complex
No
Yes
Yes
Yes
Yes

4|P age

For cells to be classed as viable they need to meet 3 basic criteria: the ability to metabolise, grow and evolve
...

Figure 1
...

(2a) Differentiation is achieved by the synthesis of new
substances or structures that modify the cell; (2b)
Communication involves the synthesis and response to chemical
signals
...
They live in specific environments, called habitats, whose conditions
vary depending on the requirements of the microbes
...
Microbial
ecology (environmental microbiology) studies the behaviour of microbes in their
natural ecosystem
...
The
chemical & physical constituents of a microbial habitat can be affected by microbial
activities, for example, the consumption of nutrients and excretion of waste
products
...

Microbial life is found in almost every environment on Earth - some microbes
(archaea & bacteria) are extremophiles which thrive in extreme conditions, in
which other microbes would not be able to do so
...


Figure 1
...
The cells are key reservoirs of essential nutrients such as carbon, phosphorus
and nitrogen
...
There are many more beneficial microbes than
the problematic, pathogenic ones, but emphasis is applied on researching the pathogenic microbes
...


Figure 1
...
There is a significant decrease in the population deaths caused by infectious microbial diseases
...

Agriculturally, some microbes are responsible for the
nitrogen cycle where they play a role in nitrogen fixation
and aid the growth and development of leguminous plants,
they enable the degradation of cellulose in the rumen of
ruminant animals, and regeneration of nutrients in the
water and soil
...


Soybean
plant

Rumen

In the food industry, microbes are predominantly
responsible for the spoilage of foods which led to a
demand in research of preservation methods, however,
some organisms are responsible for the production of dairy
products such as cheeses, yoghurts, sauerkraut, as well as
beers, pickles and breads
...
7: Nitrogen fixation process (a) and cellulose
degradation process in the rumen of grazing animals
...


6|P age



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