Lect. 1 introduction to general microbiology

General MicrobiologyGeneral Microbiology

• Information:
• Text Book
– MICROBIOLOGY, Prescott et al.,4th
, 5th
or 6th
edition
• http://highered.mcgraw-hill.com/sites/0072320419/student_view0/
• http://www.biotechnology.uwc.ac.za/StaffandStudents/Staff/Mongi.htm
• Tests and Exams:
Oral 10 %
Assign. 1 5 %
Assign. 2 5 %
Practicals 20 %
Exam 60 %

Lecture 1:
Introduction to Microbiology,
History & scope

The place of microorganisms in nature
Eukaryotes and prokaryotes
Scientific investigation and Discovery
General properties of microorganisms
Classification

• Discovery of Microorganisms:
- Invisible creatures were thought to exist long before they were observed.
- Antony van Leewenhoek (1632 –
1723) who invented the first microscope
(50 – 300x), was the first to accurately
observe and describe microorganisms.

• Microorganisms:
- Microorganisms are everywhere; almost every natural surface is colonized by
microbes, from body to ocean. Some microorganisms can live hot springs, and others in
frozen sea ice.
- Most microorganisms are harmless to humans; You swallow millions of microbes
every day with no ill effects. In fact, we are dependent on microbes to help us digest
our food.
- Microbes also keep the biosphere running by carrying out essential functions such as
decomposition of dead animals and plants. They make possible the cycles of carbon,
oxygen, nitrogen and sulfur that take place in terrestrial and aquatic systems.
- They sometimes cause diseases in man, animals and plants. They are involved in food
spoilage.
- Infectious diseases have played major roles in shaping human history (decline of
Roman Empire & conquest of the New World.
- The "Great Plague", reduced population of western Europe by 25%.
- Smallpox and other infectious diseases introduced by European explorers to the
Americas in 1500's were responsible for decimating Native American populations.
- Until late 1800's, no one had proved that infectious diseases were caused by specific
microbes.

• Spontaneous Generation Conflict:
- From earliest times, people believed that Living organisms could developed from
nonliving or decomposing matter.
- The SGT was challenged by Redi, Needham, Spallanzani
- Louis Pasteur (1822-1895) settled the conflict once for all; heated the necks of flasks
and drew them out .

• Role of Microorganisms in Disease:
- Pasteur showed that Microorganisms caused disease.
- Joseph Lister – developed system for sterile surgery
- Robert Koch (1843 – 1910) established the relationship between Bacillus anthracis
and anthrax; also isolated the bacillus that causes tuberculosis.
- Charles Chamberland (1851-1908) discovered viruses and their role in disease.
• Koch’s Postulates:
- Microorganism must be present in every case of the disease but absent from healthy
individuals.
- The suspected microorganism must be isolated and grown in pure cultures.
- The disease must result when the isolated microorganism is inoculated into a healthy
host.
- The same microorganism must be isolated from the disease host.

• Isolation of Microorganisms:
- During Koch’s studies, it became necessary to isolate suspected bacterial pathogens.
- He cultured bacteria on the sterile surfaces of cut, boiled potatoes  Not satisfactory.
- Regular liquid medium solidified by adding gelatin  gelatin melted @ T>28°C.
- Fannie Eilshemius suggested use of agar; 100°C to melt, 50 °C to solidify.
- Richard Petri developed petri dish, a container for solid culture media.
• Louis Pasteur (1822 – 1895):
- Developed vaccines for Chickenpox, anthrax, rabies
- Demonstrated that all fermentations were due to the activities of specific yeasts and
bacteria.
- Discovered that fermentative microorganisms were anaerobic and could live only
in absence of oxygen.
- Developed Pasteurization to preserve wine during storage. Important: Foods

• Other Developments…
- Winogradsky made many contributions to soil microbiology; discovered that soil
bacteria could oxidize Fe, S and ammonia to obtain energy.
- Isolated Anaerobic nitrogen-fixing bacteria; studied the decomposition of cellulose.
- Together with Beijerink, developed the enrichment-culture technique and the use of
selective media.
- Early 40’s, Microbiology established closer relationship with Genetics and
Biochemistry; microorganisms are extremely useful experimental subjects.
- e.g. Study of relationship between genes and enzymes; evidence that DNA is the
genetic material;
- Recently, Microbiology been a major contributor to the rise of Molecular Biology.
- Studies on Genetic code; mechanisms of DNA, RNA, and Protein synthesis;
regulation of gene expression; control of enzyme activity.
- Development of Recombinant DNA Technology and Genetic Engineering.

• Microbiology:
- In the broadest sense, microbiology is the study of all organisms that
are invisible to the naked eye-that is the study of microorganisms.
- Its subjects are viruses, bacteria, many algae and fungi, and protozoa.
- The importance of microbiology and microorganisms can not be
overemphasized.
- Microorganisms are necessary for the production of bread, cheese,
beer, antibiotics, vaccines, vitamins, enzymes, etc.
- Modern biotechnology rests upon a microbiological foundation.

• Scope of Microbiology:
- Many microbiologists are primarily interested in the biology of microorganisms,
while others focus on specific groups;
- Microbiology has an impact on medicine, agriculture, food science, ecology, genetics,
biochemistry, immunology, and many other fields.
- Virologists - viruses
- Bacteriologists - bacteria
- Phycologists – algae
- Mycologist -fungi
- Protozoologists – protozoa

- Medical Microbiology: deals with diseases of humans and animals; identify and plan
measures to eliminate agents causing infectious diseases.
- Immunology: study of the immune system that protects the body from pathogens.
- Agricultural Microbiology: impact of microorganisms on agriculture; combat plant
diseases that attack important food crops.
- Food and Dairy Microbiology: prevent microbial spoilage of food & transmission of
food-borne diseases (e.g. salmonellosis); use microorganisms to make food such as
cheeses, yogurts, pickles, beer, etc.
- Industrial Microbiology: using microorganisms to make products such as
antibiotics, vaccines, steroids, alcohols & other solvents, vitamins, amino acids,
enzymes, etc.
- Genetic Engineering: Engineered microorganisms used to make hormones,
antibiotics, vaccines and other products.

Plant Names & Classification
 Some learning Goals:
 1- Know what the Binomial System of Nomenclature is, how it
developed, and how it is currently used.
 2- Learn several reasons for recognizing more than two
kingdoms of living organisms.
 3- Understand the bases for Whittaker’s five-kingdoms system.
 Outline……….

Systematics
Classification of Living Things

SYSTEMATICS
 Gk systema – system + atikos – about
 Webster: the science or method of classifying,
especially taxonomy
 Raven: Scientific study of the kinds of organisms
and the relationships between them
 Judd: The science of organismal diversity,
frequently used in a sense roughly equivalent to
taxonomy

History of Classification
Early classification systems probably grouped organisms as
to whether they were beneficial or harmful. Another ancient
classification system recognized 5 animal groups - domestic
animals, wild animals, creeping animals, flying animals, and
sea animals.
ARISTOTLE -
*4th century BC (384 to322 BC)
*Greek philosopher
*divided organisms into 2 groups - plants and animals
*divided animals into blood and bloodless
*also divided animals into 3 groups according to how they moved -
walking, flying, or swimming (land, air, or water)
*his system was used into the 1600's

18th century
•Swedish scientist
•classified plants and animals according to
similarities in form
•divided living things into one of two
"kingdoms" -
•plant and animal kingdoms
•divided each of the kingdoms into smaller
groups called "genera" (plural of "genus")
•divided each genera into smaller groups
called "species"
CAROLUS LINNAEUS

•designed a system of naming organisms called
binomial ("two names") nomenclature ("system of
naming") which gave each organism 2 names -
genus (plural = genera) and species (plural =
species) names. The genus and species names
would be similar to your first and last names.
Genus is always capitalized while species is never
capitalized. To be written correctly, the scientific
name must be either underlined or written in
italics.
CAROLUS LINNAEUS

Plant Classification
 Binomial System of
Nomenclature
 Linnaeus - "founder of
plant taxonomy.“
 Credited with binomial
system and classification
hierarchy. Example:
 Chlorella vulgaris
 Genus-- always italicized or
underlined, e.g. Chlorella or
Chlorella
 Species-- always italicized or
underlined, e.g. vulgaris or
vulgaris
C. LinnaeusC. Linnaeus
1707-17781707-1778

In Aristotle's time, the living things were classified as either plants
or animals.
This 2 kingdom classification system was also used by Linnaeus
and other scientists through the middle of the twentieth century.
Today, a 5-kingdom classification system is generally accepted.
It was proposed by R. H. Whittaker in 1969.
However, this may not be the end of the story. Some scientists
have proposed that organisms be divided into even more (maybe
as many as 8) kingdoms!
Viruses are not included in any of the present 5 kingdoms - mainly
due to their many nonliving characteristics (for example, viruses
are not cells).
History of Classification
(Classification is a constantly changing, dynamic science)
5-kingdom classification system

Two kingdoms
 Kingdom : Plantae
 Kingdom : Animalia
The basis of differentiation

Three kingdoms(Haeckel(
 Kingdom : Protista

Four kingdoms(Copeland(
 Kingdom : Monera
 Kingdom : Protista

Five kingdoms
 1- Monera simplest organisms, single-celled Cyanobacteria
(blue green algae), heterotrophic
 bacteria, archaea
 2- Protista (Protoctista) single and multicelled with nucleus
 Algae, protozoa (amoebas)
 3- Fungi
 Mold, lichen
 4- Plantae multicelled photosynthetic plants
 5- Animalia multicelled animals

1. KINGDOM MONERA
* 1 cell
* no true nucleus - prokaryote (genetic material scattered
and not enclosed by a membrane)
* some move (flagellum); others don't
* some make their own food (autotrophic); others can't make
their own food (heterotrophic)
* examples - bacteria, blue-green bacteria (cyanobacteria)
Five - kingdom classification system

2. KINGDOM PROTISTA
* 1 cell
* have a true nucleus - eukaryote
* some move (cilia, flagella, pseudopodia); others don't
* some are autotrophic; others are heterotrophic
* examples - amoeba, diatom, euglena, paramecium, some
algae (unicellular), etc

3. KINGDOM FUNGI
* Multicellular
* have nuclei
* mainly do not move from place to place
* heterotrophic (food is digested outside of fungus)
* examples - mushroom, mold, puffball, shelf/bracket
fungus, yeast,

4. KINGDOM PLANTAE (plants)
*multicellular
*have nuclei
*do not move
*autotrophic
*examples - multicellular algae, mosses, ferns, flowering
plants (dandelions, roses, etc.), trees, etc

5. KINGDOM ANIMALIA (animals)
*multicellular
*have nuclei
*do move
*heterotrophic
*examples - sponge, jellyfish, insect, fish, frog, bird, man

Classification Hierarchy
Systemized classification of organisms
􀂄 Kingdom (General)
􀂄 Phylum
􀂄 Class
􀂄 Order
􀂄 Family
􀂄 Genus
􀂄 Species (Specific)

plantplant AnimalAnimal
ss
ProtozoaProtozoa
FungiFungi
MicroalgaeMicroalgae
BacteriaBacteria ActinomycetesActinomycetes
MicroorganismsMicroorganisms
EuglenaEuglena
EukaryotesEukaryotes
ProkaryotesProkaryotesRikkitssiaRikkitssia
VirusesViruses

Prokaryotic and Eukaryotic
Cells
 Prokaryotic cell structureProkaryotic cell structure
 Eukaryotic cell structureEukaryotic cell structure
 Differences between Prokaryotic &Differences between Prokaryotic &
Eukaryotic cells.Eukaryotic cells.

- Cell is defined as the fundamental living unit of any organism.
- Cell is important to produce energy for metabolism (all
chemical reactions within a cell)
- Cell can mutate (change genetically) as a result of accidental
changes in its genetic material (DNA).
- Some microorganisms are prokaryotic, some are eukaryotic, &
some are not cells at all (Viruses)
- Viruses are composed of only a few genes protected by a
protein coat, & may contain few enzymes.
- Cytology: the study of the structure and functions of cells.

Eukaryotic cellEukaryotic cell Prokaryotic cellProkaryotic cell
GramGram++
GramGram--
Cell wallCell wall
Cell (inner) membraneCell (inner) membrane Outer membraneOuter membrane
RibosomesRibosomes
Rough endoplasmicRough endoplasmic
reticulumreticulum
MitochondriaMitochondria
GranuleGranule
((e.g. animale.g. animal))
Cell wallCell wall
NucleoidNucleoid
NucleusNucleus
Cell membraneCell membrane
CapsuleCapsule
CytoplasmCytoplasm
FlagellumFlagellum
PiliPili

• Composition of the Microbial World:
-Procaryotes: relative simple morphology and
-lack true membrane delimited nucleus
- Eucaryotes: morphologically
complex with a true membrane
enclosed nucleus

Distinguishing Features of Prokaryotic Cells:
1. DNA is:
= Not enclosed within a nuclear membrane.
= A single circular chromosome.
2. Lack membrane-enclosed organelles like
mitochondria, chloroplasts, Golgi, etc.
3. Cell walls usually contain peptidoglycan, a complex
polysaccharide.
4. Divide by binary fission (absence of sexual reproduction).

Distinguishing Features of Eucaryotic
Cells:
1. DNA is:
-Enclosed within a nuclear membrane.
-Several linear chromosomes.
2. Have membrane-enclosed organelles like
mitochondria, chloroplasts, Golgi, endoplasmic
reticulum, etc.
3. Divide by mitosis.

Important Differences Between Eucaryotic and Procaryotic Cells
Procaryotes Eucaryotes
Cell size 0.2-2 um in diameter 10-100 um in diameter
Nucleus Absent Present
Membranous
Organelles Absent Present
Cell Wall Chemically complex When present, simple
Ribosomes Smaller (70S) Larger (80S) in cell
70S in organelles
DNA Single circular Multiple linear
chromosome chromosomes (histones)
Cell Division Binary fission Mitosis
Cytoskeleton Absent Present

Characteristics of Life
 Growth and development
 Reproduction and heredity
 Metabolism (synthesis, degradation)
 Movement/ moving responses
 Cell support, protection, storage
 Transport of materials into and out of cell

Living things are made of cells.
Living things obtain and use energy.
Living things grow and develop.
Living things reproduce.
Living things respond to their environment.
Living things adapt to their environment.
Main characteristics of living
things (organisms)

Small dimensions.
Eukaryotes and prokaryotes
Morphologically differ.
Metabolic flexible.
Widely distributed.
Reproduce by different methods.
Main characteristics of
microorganisms

Lect. 1 introduction to general microbiology

Lect. 1 introduction to general microbiology

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