Bacteria

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General Microbiology
Dr. Asmaa Ramadan
Prof Dr Sarah Magdy
Microbiology Department – College of Pharmacy
Arab Academy for Science, Technology and Maritime Transport (AAST)
CCS211
Lecture One
Course description
CCS211 General Microbiology
• The course provides students with a
combination of laboratory and theoretical
experience exploring the general aspects of
microbiology.
• It includes knowledge of microorganisms,
their morphology, diversity, cell structure
and function, cultural characteristics,
growth, metabolism, role of
microorganisms in infectious diseases
and microbial pathogenesis.
• It also clarifies different mechanisms of
transport across bacterial cell membrane,
metabolic pathways and physiology of
bacteria.
• The course also covers the principles of
genetic characters including DNA and RNA
structures, replication, different forms of
mutation and mutagenic agents.
• It also explores the basic concepts microbial
growth, cultivation and reproduction.
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Intended Learning Outcomes (ILOs)
Evaluation and Assessment
7 th : 30% (Quiz/coursework 5% + Practical 15% + Mid Term 10%)
12 th : 20% (Quiz/coursework 10 % + Practical 10%)
13 th : 10% (Oral 10%)
16 th : 40% (Final Written Exam 40%)
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Main Reference Book
Microbiology:An Introduction
By Tortora, Funke and Case
Introduction to Microbiology
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• Microbiology: The study of life and organisms that are too small to be seen
with the naked eye. ( at µ level ).
• Microorganisms: are minute living things that are too small to be seen with
naked eye. They must be observed using a microscope.
These microorganisms may be:
• Bacteria (Bacteriology)
• Viruses (Virology)
• Fungi (Yeasts & Molds) (Mycology)
• Parasites - Protozoa (Parasitology)
• Microscope: Latin word micro (small) + Greek word skopos (to look at).
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The minority of microorganisms are pathogenic (disease-producing), or cause
food spoilage
The majority of microorganisms help maintain the balance of life in our
environment.
Examples:
 Soil microbes help break down wastes and fix nitrogen gas.
 Gut microbes aid in food digestion in the intestine and synthesis of vitamins
K, folic acid, niacin, and vitamins B6 and B12
 Gut microbes also protect us against bacteria that cause disease by
crowding them out in the gut, producing acids that inhibit their growth, and
stimulating the immune system to fight them off.
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 Microorganisms are responsible for converting chemical elements (e.g.
carbon, nitrogen, oxygen, sulfur, and phosphorus) into forms that plants
and animals can use (recycling)
 Microorganisms are used to recycle water (sewage treatment).
 Microorganisms are used to clean up pollutants and toxic wastes
(bioremediation).
 Microorganisms also have many commercial applications:
• Synthesis of vitamins (vitamins B2 and B12), organic acids, enzymes,
alcohols (ethanol, butanol) and antibiotics.
• The food industry also uses microbes in production of vinegar, pickles,
cheese, yoghurt, bread and alcoholic beverages.
 Biotechnology applications
History of Microbiology
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Spontaneous Generation Theory
“Abiogenesis”
• Before 17th century, people believed that some forms of life or microorganisms
could arise spontaneously from non-living matter, for example
• Maggots from meat
• Mice from Grain
• Beetles from the dung
Antoni van Leeuwenhoek : ( 1632 – 1723 )
- The father of microbiology, from
Netherlands.
- The first who actually observed living
microorganisms through magnifying lenses &
drew them.
- He wrote a series of letters to the Royal
Society of London describing the
"Animalcules" he saw using his simple single
lens microscope.
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• In 1668, Francesco Redi showed that maggots don’t arise from decaying meat
• In 1858, Rudolf Virchow developed the concept of biogenesis (living cells arise only from
preexisting living cells).
“Biogenesis” theory
• Redi’s Observations: Flies
land on meat that is left
uncovered. Later, maggots
appear on meat.
• Hypothesis: Flies produce
maggots.
• Conclusion: Spontaneous
generation of maggots did
not occur.
French chemist & Microbiologist.
- He also disproved the theory of " Spontaneous Generation “
using swan-necked flasks.
- He demonstrated that microorganisms are present in air, establishing the
relation between the infection & microorganisms.
- He identified the causative organism (protozoa) causing French silk disease.
- He was best known to the general public for inventing a method to stop milk
and wine from causing sickness, pasteurization.
- He created the first vaccine for rabies and anthrax.
- These discoveries form the basis of aseptic techniques , which are now the
standard practice in laboratory and many medical procedures.
Louis Pasteur : ( 1822 – 1895 )
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In 1861, Pasteur demonstrated that microorganisms are present in
the air and can contaminate sterile solutions.
Basis of
aseptic
techniques
Joseph Lister
- English surgeon.
- Applied the aseptic techniques
to control infections in surgeries
& in treating surgical wounds
that set by Louis Pasteur.
Robert koch
1. A specific organism can always be found in
association with a given disease
2. The organism can be isolated and grown in pure
culture in laboratory
3. The organism from pure culture will produce the
disease when inoculated into a susceptible animal
4. It is possible to recover the same organism in pure
culture from experimentally infected animal.
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Nomenclature & Classification of
Microorganisms
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Taxonomy: Science of identifying,
classifying and naming of living
organisms
• There are 7 levels of taxonomy. Each is
more specific than the previous and
includes fewer organisms.
Example of Taxonomic classification of E.coli
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Taxonomy: Science of identifying, classifying and
naming of living organisms
Taxonomy divides organisms into 6
kingdoms
A)Prokaryotes, which includes:
i- Bacteria
ii- Archaea
B) Eukaryotes, which includes:
i- Protists
ii- Fungi
iii- Plants
iv- Animals
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Prokaryotic Cell Structure
Eukaryotic Cell Structure
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Importance of taxonomy in microbiology:
1- Identifying the causative agent of a disease.
2- Which organisms are closely related to each other.
3- Selecting the drug of choice for the treatment of such disease.
Nomenclature of microorganisms
• Scientific names for organisms are latinized.
• Scientific nomenclature assigns each organism two names:
• the genus (plural: genera) is the first name and is always capitalized
• the species name follows and is not capitalized.
• The organism is referred to by both the genus and the species names, and both
names are underlined or italicized
• They can be abbreviated with the initial of the genus followed by the species.
Staphylococcus aureus (S.aureus)
Escherichia coli (E.coli)
Candida albicans (C.albicans)
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Classical Classification of bacteria
a) as Prokaryotes
b) According to shape , size & arrangement
c) Nomenclature ( genus & species )
d) Gram staining characteristics ( Gram positive or Gram negative )
Recent classification (taxonomy) is based on molecular biology
a) Percentage of Guanine & Cytosine in the chromosome.
b) Gene sequencing for knowing the sequence of the nitrogenous bases on genes ( A, G, C, T)
c) Comparing DNA patterns using gel electrophoresis technique.
1. Bacteria
Structure of a bacterial cell
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Classification according to Shape and Arrangements of
Bacteria
• Most bacteria range from 0.2 to 2.0 μm in diameter and from 2 to 8 μm in
length.
• They have three basic shapes:
• spherical coccus (plural: cocci, meaning berries),
• rod-shaped bacillus (plural: bacilli, meaning little staffs),
• spiral.
The Size, Shape, and Arrangement of Bacterial Cells
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Cocci
• Cocci are usually round but can be oval, elongated, or flattened
on one side.
• When cocci divide to reproduce, the cells can remain attached
to one another.
• Cocci that remain in pairs after dividing are called
diplococci.
• Those that remain attached in chain-like patterns are called
streptococci.
• Those that divide in two planes and remain in groups of
four are known as tetrads.
• Those that divide in three planes and remain attached in
cubelike groups of eight are called sarcinae.
• Those that divide in multiple planes and form grape-like
clusters are called staphylococci.
Bacilli
• Rod-shaped
• Bacilli divide only across their short axis, so there are
fewer groupings of bacilli than of cocci. Most bacilli
appear as single rods, called single bacilli.
• Diplobacilli appear in pairs after division, and
streptobacilli occur in chains.
• Some bacilli look like straws, others have tapered ends,
like cigars.
• Others are oval and look so much like cocci that they are
called coccobacilli.
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Spiral bacteria
• Spiral bacteria have one or more twists;
they are never straight.
• Bacteria that look like curved rods (or comma
shaped) are called vibrios.
• Others, called spirilla, have a helical shape,
like a corkscrew, and fairly rigid bodies.
• Yet another group of spirals are helical and
flexible; they are called spirochetes.
In addition to the three basic shapes, there are :
Star-shaped cells (genus Stella);
Rectangular, flat cells (halophilic archaea) of the genus Haloarcula ;
Triangular cells
Pleomorphic, which means they can have many shapes,
not just one
e.g. Corynebacterium.
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2. Archaea
- Like bacteria, archaea consist of prokaryotic cells, but if
they have cell walls, the walls lack peptidoglycan.
- Archaea, often found in extreme environments, are
divided into three main groups:
i) The methanogens produce methane as a waste product
from respiration.
ii) The extreme halophiles (halo = salt; philic = loving) live in
extremely salty environments such as the Dead Sea.
iii) The extreme thermophiles (therm = heat) live in hot
sulfurous water, such as hot springs at Yellowstone National
Park.
- Archaea are not known to cause disease in humans.
3. Fungi
- Eukaryotes
- Organisms in the Kingdom Fungi may be unicellular (Yeast) or
multicellular (Mold).
- Large multicellular fungi, such as mushrooms, may look
somewhat like plants, but unlike most plants, fungi cannot carry
out photosynthesis.
- Molds form visible masses called mycelia, which are composed
of long filaments (hyphae) that branch and intertwine.
- The unicellular forms of fungi, yeasts, are oval microorganisms
that are larger than bacteria.
- True fungi have cell walls composed primarily of a substance
called chitin.
- Fungi can reproduce sexually or asexually.
- They obtain nourishment by absorbing solutions of organic
material from their environment.
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4. Algae
- Algae (singular: alga) are photosynthetic eukaryotes
with a wide variety of shapes and both sexual and
asexual reproductive forms.
- The algae of interest to microbiologists are usually
unicellular.
- The cell walls of many algae, are composed of a
carbohydrate called cellulose.
- Algae are abundant in freshwater and salt water, in
soil, and in association with plants.
5. Viruses
- So small ……… can be seen only with an electron microscope.
- They are acellular (not cellular).
- Contains : A Core made of only one type of Nucleic acid, either
DNA or RNA. This core is surrounded by a protein coat (Capsid),
which is sometimes encased by a lipid membrane called an
Envelope.
- Viruses can reproduce only by using the cellular machinery of
other organisms (obligate intracellular)
- Viruses are considered to be living only when they multiply
within host cells they infect.
- Viruses are not considered to be living because they are inert
outside living hosts.
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6. Parasites
a. Protozoa
- Unicellular, eukaryotic
- Protozoa move by pseudopods, flagella, or cilia.
- Protozoa have a variety of shapes and live either
as free entities or as parasites (organisms that
derive nutrients from living hosts) that absorb or
ingest organic compounds from their environment.
- Some protozoa are photosynthetic: They use light
as a source of energy and carbon dioxide as their
chief source of carbon to produce sugars.
- Protozoa can reproduce sexually or asexually.
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b. Metazoa (Multicellular Animal Parasites)
- Are not strictly microorganisms but of
medical importance.
- Animal parasites are eukaryotes.
- E.g. the flatworms and the roundworms,
collectively called Helminths.
- During some stages of their life cycle,
helminths are microscopic in size.
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