Download General Microbiology

General Microbiology
BIO 231
Prof. Dr. Adel Ahmed El-Mehalawy
Microorganisms:
Thery are minute organisms which cannot be seen by naked eye.
They require microscope.
Discovery of microorganisms:
1- Van Leevanhock: He discovered simple microscope (one lens) and
examine a drop of water.
2- Robert Hooke: He discovered the compound microscope (more
than one lens).
3- Muller: He examined microorganisms in rotted substances and
water.
4- Spallinzi: He boiled water in a closed flask for one hour and he
proved that this water did not contain microorganisms.
5- Schwman: He proved that yeast cells are the cause of alcoholic
fermentation of sugar solution.
6- Pasteur: He discovered the pasteurization of milk by heating milk
at 145of for 30 minutes.
7- Robert Koch: He isolated rod shaped bacteria which cause Anthrax
from the blood of infected animals.
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Sources of Microorganisms
1- water
2- Air
3- Soil
4- Milk
5- Food
6- Sewage.
Methods of Sterilization
A- Physical Methods:
1- By heat:
a) dry heat by oven.
b) Moist heat by autoclave.
2- Pasteurization: by boiling at 65oC for 30 minutes.
3- Radiation: a) by ultaviolet light.
b) by ionizing radiation.
4- Filtration: to remove spores of microorganisms and not kill them.
B- Chemical Methods:
These chemicals are used to kill spores (bactericidal) or to prevent
the growth of spores (bacteriostatic). These chemicals are used in case of
substances which are sensitive to heat.
1- Salts: used in high concentrations.
2- Acids or alkalies: Make the pH of the medium unfavorable for
groeth.
3- Alcohols: used at concentration 10%.
Nutrient Medium
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The nutrient medium used for growth of microorganisms must
contain the following constituents:
1- Carbon and Nitrogen sources.
2- Phosphate and sulphate.
3- Microelements ans macroelements.
Importance of Microorganisms
I- In Industry:
Some microorgansims are used in industry such as yeasts. They are
used in alcoholic fermentation to produce alcohol and CO 2 from sugar
solution. Yeasts are also used in baking (bread making) which help in
raising the dough. Somw microorganisms are used to produce dyes.
II- In Medicine:
Microorganisms like bacteria and fungi cause serious diseases to
man and animals.
a- Bacteria: cause fever, pulmonary infection and intestinal infection.
b- Fungi: cause a disease to the respiratory system (Aspergillosis).
Cause diseases to the skin (dermatophytosis).
III- In Agriculture:
a- Bacteria: Cause diseases such as common scab and crown gall.
b- Fungi Cause diseases such as powdery mildew, downy mildew,
rusts, smuts, rotts and wilts.
Useful Microorganism:
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Some microorganisms are useful and are used to produce
antibiotics such as Penicillin (Penicillium) and streptomycin
(Streptomyces).
Growth of Microorganisms
Growth: It is the increase in number of cells.
Rate of Growth: It is the difference in growth between two
successive periods.
Each organism has its typical growth curve, consisting of the
following phases:
1- Lag Phase:It is the period of no growth.
2- Log Phase:
It is the period of rapid growth.
3-Stationary Phase:
It is the period in which the
number of living cells equals
the number of dead cells.
4- Death Phase:
It is the period in which the number
of dead cells is greater than the
number of living cells.
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Factors Affecting Growth
I- Temperature:
According to temperature requirement, microorganisms are
classified into the following groups:
↓
↓
Pyschrophiles
Prefer low temp.
(0-15oC).
↓
↓
Mesophiles
Prefer medium temp.
(15-35oC).
Thermophiles
Prefer hogh temp.
(35-55oC).
2- Aeration:
Acoording to oxygen requirement, microoorganisms are classified
into the following groups:
↓
↓
Aeriobic
↓
Facultative
Live only in presence can live in presence or
of oxygen.
absence of oxygen.
↓
Anaerobic
live only in absence
of oxygen.
3-pH- value:
According to pH- value, microorganisms are classified into the
following groups:
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↓
↓
Acidophilic
Prefer acidic medium
(pH 4-5).
↓
↓
Mesophilic
prefer medium pH
(pH 6.5-7).
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Alkalophilic
prefer alkaline medium
(pH 8-9).
Viruses
Viruses differe from microorganisms in the following properties:
1- They contain one kind of nucleic acid, either DNA or RNA.
2- They are unable to reproduce outside living cells.
Outside the living cells, it is called a virion or virus particle
Structure:
The virus particle consists of nucleic acid and a protein coat known
as “capsis” (nucleocapsid). Sometimes, there is a membrane.
Therefore, the virus may be naked or covered by a membrane.
Capsid:
Capsid consists of subunits called capsomers. The capsomers may
be helical or cubical.
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Classification of viruses:
Viruses are classified according to their hosts into the following groups:
↓
↓
↓
Animal viruses
Plant viruses
They cause many diseases to
They cause many diseases to
animals and humans, such as
plants such as tobacco mosaic
Influenza, Tumor.
Virus (TMV).
Bacterial Viruses (Bacteriophage)
They are viruses which use bacterial cells as hosts.
Structure of bacteriophage:
It consists of polyhedral head and a tail.
1-Head:
It consists of capsomers and contain DNA.
2- Hollow stylus.
3- Basal part.
4- Adsorption spikes.
Cultivation of viruses
1- Homogenization:
It is the breakdown of tissue into small units.
2- Trypsinization:
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It is the breakdown of small units into cells. This was carried out
bybreaking the cementing material which join the cells, by proteolytic
enzyme.
3- Washing:
The cells are washed with salt solution.
4- The washed cells are cultivated in a suitable growth medium.
Purification of viruses
1- Ultrafiltration:
The suspension containing viruses passes through suitable filter
which allow the virus particle to pass.
2- Ultra-centrifugation:
The suspension containing viruses may be purified by two- step
centrifugation process. The first step was carried out at low speed and
the second step was carried out at high spped.
3- Precipitation:
This process was carried out by using chemical agents like ethanol
or ammonium sulphate.
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Reproduction of viruses
1-Adsorption and penetration:
The viral particle attach itself to the host cell and penetrate this
host.
2- Nucleic acid replication:
Each part form its complementary part.
3- Maturation:
After replication, the host produces viral protein (capsomer).
4- Release:After maturation, the virus releases from the host cell.
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Bacteria
They are unicellular microorganisms ( the cell perform all the vital
processes, such as reproduction, nutrition, etc.).
Structure:
1- Cell wall:
It protects the cell from the external
environment, and it defines the shape of the cell.
2- Flagella:
They are organs of motility.
3- Cytoplasm:
It is the cell sap containing ribosomes.
4- Nucleus:
It is primitive and consists of DNA.
Shape:
I- Spherical: They are also called cocci.
a- Monococcus: Single spherical cell.
b- Diplococcus: Single cell divides one time
in one direction.
c- Tetracoccus: Single cell divides two times
in two directions.
d- Sarcina: Single cell divides three times in
three directions.
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e- Streptococcus: Single cell divides several
times in one direction.
f- Staphylococcus: Single cell divides several
times in several directions.
II- Rod- shaped: They are also called bacilli.
a- Monobacillus: Single rod-shaped cell.
b- Diplobacillus: Single cell divides one
time in one direction.
c- Streptobacillus: Single cell divides several
times in one direction.
III- Curved rods: There are two types:
a- Vivrio: which consists of one turn.
b- Spirillum: which consists of more than
one turn.
Motility of bacteria:
Some species of bacteria are motile by means of flagella.
1- Monopolar: with a single flagellum at
one pole of the cell.
2- Bipolar: with a single flagellum at
both poles of the cell.
3- Lophotrichous: with a single tuft of
flagella at one pole of the cell.
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4- Amphitrichous: with a tuft of flagella at
both poles of the cell.
5- Peritrichous: with flagella over the entire
surface of the cell.
Staining of Bacteria
1- Make a bacterial suspension.
2- Put a drop of the suspension on a clean slide and spread it.
3- Fix on a gentle flame.
4- Put the dye (Crystal violet) for one minute.
5- Wash with tap water.
6- Put safranin for 30 second.
7- Wash with tap water.
8- Dry on a gentle flame.
9- Put a drop of oil and examine under microscope.
Spores in bacteria
↓
↓
↓
Spore-former
Non-spore former
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Spore former:
I- Position:
↓
↓
↓
Polar
↓
Subpolar
Central
II- Size:
↓
↓
Smaller than
↓
↓
like the cell
the cell.
larger than
the cell.
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Fungi
General Characters:
1- They are heterotrophic (can not synthesize their own food).
2- They are eukaryotes (have a true nucleus).
3- They have cell walls.
4- They reproduce sexually and asexually by means of spores.
Thallus:
The body of the fungus is called thallus which consists of fine
threads called “hyphae”, the hyphae interconnect to form what is called
“mycelium”. The mycelium may be
↓
↓
Acellular
Which consists of multinucleate
protoplasmic mass called
“plasmodium”.
↓
Cellular
which may be unicellular
(single cell or holocarpic),
or multicellular (many
cells or eucarpic).
The spore germinate giving germ tube which enlarge giving a
‘hypha”. Many hyphae interconnect to form a “mycelium”.
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The hyphae may be
↓
↓
↓
Septate
Non-septate
(have septa)
(have no septa)
Structure of the fungal celll:
1- Fungal cell wall:
It consists of polysaccharides, proteins and lipids.
Function of cell wall:
a- It determines the shape of the cell.
b- It protects the cell from the external environment.
2- Septa:They are found in septate hyphae. They protect the cell from
dry conditions. Thus, septate fungi are more tolerant to water stress than
non- septate fungi.
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3- Plasma membrane:
It consists of lipids, proteins and sterols. It contains “ergosterol”. Thus,
fungi are sensitive to fungicides due to presence of ergosterol.
4- Nucleus:
It is a well defined and complete nucleus. It consists of a nuclear
membrane, nuclear sap and a nucleolus containing RNA.
5- Secretory system
It consists of Golgi apparatus, endoplasmic reticulum and vesicles.
6- Vacuoles:
It has many functions:
a- Storage of compounds.
b- Accunulation of phosphate.
c- Containing proteases for brakdown of proteins.
d- Regulation of cellular pH.
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Reproduction of fungi
Asexual reproduction
Types of asexual spores:
↓
↓
Sporangiospores
They are formed inside a sac
Called “sporangia”.
↓
___________________________________
↓
↓
Uniflagellate
Biflagellate
Have single flagellum
have two flagella
↓
one anterior (tensil-type)
______________________ and one posterior (whiplash
↓
↓ type).
Anterior
Posterior
(tensil-type)
(whiplash-type)
↓
Conidia
They are formed free
________________________________________________________
↓
↓
Thallospores
Conidiospores
They are formed by transformation
Of organs.
↓
They are formed as new elements
___________________________________
↓
Arthrospores
Formed by fragmentation
↓
Chlamydospores
formed by swelling of cells
↓
↓
Blastospores
Phialospores
Formed as buds.
Formed on a flask structures called
“phialides”.
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Sexual Reproduction
Fungi reproduce sexually on three successive steps:
1- Plasmogamy: It is the unionof two protoplasmic masses (male
gamete and female gamete).
2- Karyogamy: It is the union of two different nuclei (one from male
and the other from female).
3- Meiosis followed by mitosis: Meiosis is to reduce the diploid number
of chromosomes (2 n) to the haploid number ( n ). Mitosis is to increase
the haploid number of chromosomes.
♀
♂
(n)
(n)
(2 n)
( n)
(n)
(n)
(n)
(n)
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(n)
Classification of fungi
Kingdom: Protista
Kingdom: Eumycota
1- The thallus may be cellular or
1- The thallus is cellular ( septate or non-
acellular.
Septate).
2- Spores are motile.
2- Spores are non- motile.
Phylum
__________________________________________________________
Chytridiomycota
Hyphochytridiomycota
With posterior
Whiplash-type flagellum.
with anterior tensil-typeFlagellum.
Oomycota
with one anterior and one
Posterior flagella.
Subkingdom
______________________________________________________________________________
Zygomyxcota
Dikaryomycota
1- Mycelium is non-septate.
1- Mycelium is septate.
2- Karyogamy occurs directly.
2- Karyogamy is delayed.
Phylum
______________________________________________________________________________
Ascomycota
Basidiomycota
Spores are formed inside a sac called (Ascus).
Spores are formed on a flate structure
Called (basidium).
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Phylum: Oomycota
General Characters:
1- Presence of non-septate mycelium.
2- Presence of motile zoospores.
3- Presence of biflagellate zoospores.
Albugo portulacae:
1- It causes a disease called white rust.
2- It has non-septate mycelium.
3- It has a club-shaped sporangiospore.
4- The sporangiospore carry a chain
of sporangia.
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Plasmopara
1- causes a disease
called downy mildew.
2- Presence of non-septate
mycelium.
Peronospora
1- causes a disease
called downy mildew.
2- Presence of non-septate
Mycelium.
Bremia
1- causes a disease
called downy mildew.
2- Presence of nonSeptate mycelium.
3- Presence of mono-
3- Presence of dichoto-
3- Presence of dichoto-
podially branched
mously branched
mously branched
sporangiophore.
Sporangiophore.
Sporangiophores.
4- Presence of acute tips.
4- Presence of discshaped tips.
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Subkingdom: Zygomycota
General Characters:
1- Thallus is cellular.
2- Hyphae are non-septate.
3- Spores are non-motile.
4- Karyogamy occurs directly.
Rhizopus
Mucor
1- Saprophytic.
1- Saprophytic.
2- Presence of non-septate
2- Presence of non-
mycelium.
3- Presence of three sporangio-
septate mycelium.
3- Presence of one sporangiophore.
Phores.
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Subkingdom: Dikaryomycota
General Characters:
1- Thallus is cellular
2- Hyphae are septate.
3- Spores are non-motile.
4- Karyogamy is delayed.
Phylum: Ascomycota
General Characters:
1- Thallus is cellular.
2- Hyphae are septate.
3- Spores are non motile.
4- Karyogamy is delayed.
5- Spores are formed inside a sac called “ascus”, each ascus contain 4-8
ascospores.
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Leveillula
Erysiphe
Sphaerotheca
1- Cause a disease called
1- cause a disease called
1- cause a disease called
powdery mildew.
powdery mildew.
powdery mildew.
2- Presence of septate
2- presence of septate
mycelium.
mycelium.
2- Presence of septate
mycelium.
3- Presence of single
3- Presence of single
3- Presence of single
conidiophore.
conidiophore.
Conidiophore.
4- Conidiophore carry
4- Conidiophore carry
4- Conidiophore carry
single conidium.
achain of conidia.
a chain of conidia.
5- Conidiophore is short.
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5- Conidiophore is long.
Aspergillus
Penicillium
1- Saprophyte
1- Saprophyte
2- Presence of septate
2- Presence of septate
mycelium.
mycelium.
3- Presence of unbranched
3- Presence of branched
conidiophore.
conidiophore.
4- Conidiophore ends with
4- Each branch ends with
a vesicle carrying phialides.
a phialide.
5- Phialide carry a chain of
5- Phialide carry a chain
conidia.
conidia.
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Phylum: Basidiomycota
General Characters:
1- Thallus is cellular.
2- Hyphae are septate.
3- Spores are non-motile.
4- Karyogamy is delayed.
5- Spores are formed on a flate structure called basidium.
Puccinia graminis
General Characters:
1- Causes a disease called black stem rust.
2- Mycelium is septate.
3- During its life cycle, it produces 5 types of spores:
a- Basidiospores:
Unicellular, Uninucleate, non-stalked and minute in size.
b- Pycniospores:
Unicellular, uninucleate, non-stalked formed
inside a pycnium.
c- Aeciospores:
Unicellular, binucleate, non-stalked formed
inside aecium.
d- Urediospores:
Unicellular, binucleate, stalked and double-walled.
e- Teliospores:
Bicellular, stalked and thick-walled.
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