Transcript Chapter 5 Diversity of Microorganisms Eucaryotic Microbes

CHAPTER 1
MICROBIOLOGY FOR THE
HEALTH SCIENCES
What is Microbiology?
Biology
Bio
Logy
Microbiology
Micro
Living organisms
Study of
very small
Definition
• Microbiology: is the study of
very small living organisms
called microorganisms or
microbes.
• Microorganisms are
ubiquitous, they are present
and distributed everywhere.
There are many categories:
• Viruses:
infectious agents or particles (aids,flu,
measles, common cold….etc)
• Bacteria
(Anthrax, botulism, cholera, leprosy,
diphtheria)
• Fungi
(allergies, meningitis, tinea, yeast vaginitis)
• Algae
(intoxication)
• Protozoa
(amebic dysentery, malaria,
giardiasis)
Pathogens: Disease causing
microorganisms 3% of all
microbes cause disease and
called microbial enemies
Nonpathogen: Microorganisms not
causing disease called the
microbial allies sometimes are
beneficial sometimes are not
Why Study Microbiology?
Because Microorganisms play very
significant roles in our lives.
HOW?
1.Living in and on our body
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Epithelial cells + nerve cells +muscle cells=10 trillion cell
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The number of microbes is 10 times =100 trillion microbes
• Indigenous microflora
1. inhibit, prevent or reduce the growth of pathogens
2. depleting the food supply
3.secreting materials (waste products-toxins- antibiotics)
2.Opportunistic pathogens (opportunists)
Microorganisms awaiting an opportunity to cause
disease
3.Microorganisms essential for life
Algae and cyanobacteria are groups of photosynthetic
bacteria that Produce oxygen more than plants
4. Decomposition of dead organisms and waste
products of living organisms
Decomposers or saprophytes
Saprophytes are organisms that lives on dead and or
decaying organic matter necessary for the growth of
plants
5. Decomposition of industrial wastes
By a process called Bioremediation
(using genetically engineered microorganisms to clean
up industrial wastes )
6. Involving in elemental cycles (C, N, O, S, P)
Very important to farmers and gardeners (microbial
ecology)
e.g
nitrogen => ammonia => nitrite=> nitrate
in soil
7.Food chain
Algae and bacteria are the food of tiny animals
8. Digestion
Microorganisms help in digestion as well producing
valuable substances
E.coli => production of vitamins K and B1
Termites which eat woods has
cellulose eating
protozoa
9. Biotechnology
Using microorganisms in various food and beverage
industry
10. Production of antibiotics (bacteria and
fungi)
It is used to treat patients with infectious diseases
“Antibiotic”: is a substance produced by
microorganisms that is effective in killing or
inhibiting the growth of other microorganisms
11. Microbes essential in Genetic engineering
Insulin , growth hormones , materials used for vaccine
12. Microbial cell used as cell model
Helps the scientist to learn a lot about the structure
and function
Microorganisms cause two categories of
disease
1. Infectious disease =>
when a pathogen colonies the body
and causes disease. Cause more
illness and death in the world after
heart and cancer disease
2. Microbial intoxication =>
when a person ingest a poisonous
substances (toxin) produced by
microorganisms
For this reason nurses should be aware of the following
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Pathogens that cause diseases
Sources of pathogens
How diseases are transmitted
How to protect yourself
How to protect your patient
Harmful microorganisms may be transferred from:
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Health workers to Patients
Patients
to Patients
Patients
to Healthcare workers
Patients
to Visitors
Contaminated devices, instrument, syringes to Patients
Contaminated bedding, clothes, dishes, food to Patients
HOW TO LIMIT?
Sterile, Aseptic, Antiseptic
techniques should be used in
hospitals, nursing rooms,
operating rooms, laboratories.
• MICROBIOLOGIST:
A scientist who study tiny organisms (microorganisms)
• Bacteriologist=> Bacteriology
• Phycologist => Phycology
• Protozoologist => Protozoology
• Mycologist => Mycology
• Virologist => Virology
NB: Virologist study not only viruses
but also smaller acellular infectious
agents “Prions & Viroids”
The Study of Applied Microbiology
1. Agricultural Microbiology
To study the beneficial and harmful roles of microbes in soil for
plants
2. Biotechnology (Industrial Microbiology)
The use of microorganisms in industry
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Production of beer, wine, alcohol
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Production of organic materials (enzymes, vitamins, antibiotic
SUBSTRATE= >microorganism=> PRODUCT
3. Environmental Microbiology & Bioremediation
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Water and sewage treatment
Purification of wastewater
Breaking down of metals and minerals by utilizing Fe, S
bacteria
Bioremediation: clean up landfills, industrial wastes, toxic
wastes
4. Medical and Clinical Microbiology (diagnostic of
clinical microbiology)
It is the study of: pathogens, diseases they cause, body’s defenses against diseases
5. Microbial Genetics and Genetic Engineering
It is the study of Microbial DNA, Chromosomes, Gene and Plasmids ( small circular molecules of
extrachromosomal DNA)
6. Microbial Physiology
It is to study the structure and functions of microbial cells
7. Paleomicrobiology
To study the ancient microbes
Paleomicrobiologist found that Mycobacterium tuberculosis DNA, in Egyptian mummies and proved that
tuberculosis existed as 3000 BC.
8. Parasitology
It is the study of the parasite and its life cycle to discover the best way to control and
treat disease they cause.
PARASITE: any organism lives on or in another living organisms.
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But the indigenous microflora (viruses or bacteria live on or in human
body are not parasites)
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Parasite categories are: Protozoa, Helminths( parasite worms) and
arthropods (insects and arachnids)
9. Sanitary Microbiology
It is the study of:
Disposal of garbage and sewage, Purification and
processing of water supply to be drinkable and
proper food handling procedures are enforced.
10. Veterinary Microbiology
It is the study of infectious diseases in animals
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Production of food from livestock
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Care of pets
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Transmission of diseases from animals to
humans
NB: Zoonoses or Zoonotic diseases:
Infectious diseases of humans that are acquired from
animal sources.
Pioneers in the Science of Microbiology
Anton van Leeuvenhoek
The first scientist who see the bacteria and
protozoa
The father of Microbiology
The father of Bacteriology
The father of Protozoology
Not a trained scientist
Ground tiny glass lenses => single lens
microscope (simple microscope)
Observed variety of tiny creatures
(animalcules) by: Scrapings from his
teeth, water from ponds, blood,
sperm, diarrheal stools
From his observation scientist believed that
life could develop spontaneously from
inanimate substances such as decaying
corpses, soil, gases. This is called
ABIOGENESIS
• Abiogenesis Theory (spontaneous
generation) :
That life can arise spontaneously
from nonliving material
After 2 centuries scientist discover the theory of
• Biogenesis Theory : Life can only
arise from preexisting life
Louis Pasteur
Many valuable contributions
• Fermentation due to wine contamination
• Destroy the theory of spontaneous
generation
• Discovered aerobes and anaerobes
• Developed Pasteurization
• Discover the infectious agents that were
causing the silk worm disease (crippling
the silk industry in France) and how to
prevent it
• Specificity: Anthrax=> Bacillus anthracis
• Tuberculosis=> Mycobacterium
tuberculosis
• Change in hospital practices to minimize
the spread of pathogen
• Developed vaccines against many
different diseases (rabies)
Robert Koch
Made numerous contributions
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Proved that Bacillus anthracis is the cause
of Anthrax
Discover that Bacillus anthracis produces
spores, capable of resisting hard
conditions
Many contributions to the germ theory of
disease.
Developed methods of fixing, staining and
photographing bacteria
Developed methods of cultivating bacteria
on solid media R.J. Petri (Petri dish) Frau
Hess (agar from seaweed) to obtain pure
culture
Discover Mycobacterium tuberculosis =>
Tuberculosis
Vibrio cholera => Cholera
Developed a skin test valuable in diagnosis
tuberculosis by the detection of tuberculin
(protein derived from M. tuberculosis)
Koch’s Postulates
• Microorganisms must be found in all cases of
disease and not present in healthy animals or
humans
• Microorganisms must be isolated from diseased
animal or human and grow in pure culture in
the lab.
• If inoculated into healthy susceptible lab animals
the same disease must be produced
• Also must be recovered from this animal and
grown again in pure culture
Exceptions to Koch’s Postulates
• It is necessary to culture pathogen in the lab (vitro), in or
on artificial culture media But
1.Viruses 2. Rickttsias (bacteria) 3.Chlamydias(bac)
Are obligate intracellular pathogens or parasites, they can
only survive and multiply within living cells
(embryonated chicken eggs)
e.g.: Leprosy => Mycobacterium lepry
Syphilis => Treponema pallidum (spirochetes)
• Fastidious : Microorganisms having complex and
demanding nutritional requirements (vitamins, amino
acids, other nutrients)
• Specificity of Microorganisms (No human volunteers)
• Synergistic infections
Diseases caused not only by one M.O.
Microbiologist cannot obtain this kind of synergism
• Some M.O. altered when cultured in vitro and
become less pathogenic or nonpathogenic and the
infected animals are no longer pathogens after being
cultured.
• Not all diseases caused by M.O.
Inherited => abnormalities in chromosomes e.g. sickle
cell anemia
Diabetes => malfunction of liver
Lung and skin cancer => environmental factors
CHAPTER 2
Tools for investigating
Microorganisms
The Metric System ( to express the sizes of
microorganisms)
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Meter (M) = 39.4 inches; 3.4 inches > yard
1M = 10 decimeter
1M = 100 cm
1M = 1000mm
1M = 1000,000 µm
1M =1000,000,000 nm
1M =10,000,000,000 A
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Coccus , cocci =
Bacillus, bacilli =
but virus
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Protozoa
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Yeast
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Septate hyphae =
Aseptate hyphae =
Chlamydomonas =
1µm
1 µm wide and 3 µm long
10-300nm
2000µm
3-5 µm
2-15 µm
10-30 µm
5-12 µm
Microscopes
A microscope is an optical instrument
that is used to observe tiny objects,
often objects that cannot be seen at all
with unaided eye.
Types of Microscopes
• Simple Microscope: A microscope
containing only one magnifying lens.
3-20 times magnification.
• Compound Microscope: A microscope
that contains more than one
magnification lens. 1000 times
Bright Field Microscope (compound
light microscope)
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Use a source of light
The wavelength of visible light
approximately 0.45µm
The object to be seen must not
be smaller than the half
wavelength of visible light
Resolution or resolving power :
which is the ability of the lens
system to distinguish two
adjacent objects
Resolving power of unaided
eye =0.2mm
Resolving power of compound
light microscope=1000 times
of human unaided eye
Dark Field Microscopes
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It is used if the object
thinner than 0.2 µm
which is below or
beneath the resolution
of a bright field
microscope
Phase Contrast Microscopes
• To observe unstained
living microorganisms
• Because light refracted by
living cells is different
from the light refracted by
the surrounding medium
so there is a difference in
the refractive index
Fluorescence Microscopes
• Depend on UV light source
• UV light strikes certain dyes
and pigments which emit a
longer wavelength light
causing them to glow against
a dark background
• It is used in immunology
laboratory to demonstrate the
antigen antibody reaction
Electron Microscopes
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Rabies and smallpox viruses cannot be
seen with the above microscopes
Cannot see the living organisms due to
harsh processing of specimen
It uses an electron beam as a source of
illumination and magnets to focus the
beam
Wavelength of electron is shorter than
the visible light (100,000 times shorter)
Having greater resolving power
Types of Electron Microscope
Transmission Electron Microscope
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Magnify up 1 million times >1000X
than compound microscope and the
resolving power is 0.2nm
Scanning Electron Microscope
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Resolving power 20nm
Chapter 3
Cell Structure and
Taxonomy
Cell:
• Is the fundamental living unit of any organism because the
cell exhibits the basic characteristics of life
• It obtains food (nutrients) from the environment to
produce energy for metabolism and other activities
• Metabolism : is all the chemical reactions that occur within
a cell, to be able to grow and reproduce and respond to
stimuli (light, heat, cold….).
• A cell can mutate (change genetically) in the DNA that
makes the genes of its chromosome
Organelles: tiny organ-like structures
• Important to study the cell to affect the microbe not the cell
Types of Cells
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Prokaryotes (prokaryotic cells) e.g.: Bacteria, Achaean
Eukaryotes (eukaryotic cells) e.g.: algae, protozoa, fungi, plants,
animals
Viruses:
• Composed of few genes protected by a protein coat
• Viruses depend on the energy and metabolic machinery of a host
cell in order to reproduce
• Viruses are acellular (not composed of cells) so they are not even
prokaryotes
Cytology: Is the study of the structure and
function of cells
Eucaryotic Cell Structure
Eucaryotes (eu= true; caryo= nucleus)
• Means have a true nucleus
• Their DNA is enclosed by a nuclear
membrane
• Diameter 10-30µm, 10 times larger
than prokaryote
Cell Membrane:
• The cell is enclosed and held intact
by it
• Known as plasma, or cytoplasmic
or cellular membrane
• Composed of large molecules of
protein and phospholipids
• It is like a skin (around the cell)
• Separating the contents of the cell
from the outside world
• It regulates the passage of
nutrients, wastes products, and
secretions into and out of the cell
• It has the selective permeability
Nucleus: (pl:nuclei)
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Controls and integrates the function of the
entire cell (command center) of the cell
Its components are Nucleoplasm, chromosomes,
nuclear membrane
Chromosomes: embedded or suspended in the
nucleoplasm
Nuclear membrane: skin around nucleus, it
contains holes known as (nuclear pore) through
which is large molecules can enter and exit
The chromosome consist of linear DNA and
protein
Genes are located along the DNA, which
contains the genetic information
Most gene products are proteins
Genotype or genome: is a complete collection of
genes to an organism
Number of chromosomes differ from one species
to another human 46 chromosomes(23 pairs),
consisting of thousand of genes(300,000 genes)
Cytoplasm
• Most of the cell metabolic reactions occur in it
• A semifluid, gelatinous, nutrient matrix
• Within the cytoplasm are found storage
granules and organelles (endoplasmic
reticulum, ribosomes, Golgi complexes,
mitochondria, centrioles, microtubules,
lysosomes
• These organelles has a highly specific function
• All the functions are interrelated to maintain
the cell to perform its activities
Endoplasmic Reticulum (ER)
• Highly convoluted system of
membranes
• Interconnected and arranged
to form transport network
• Some of ER has a rough,
granular appearance and
known as rough endoplasmic
reticulum (RER)
• This roughness is due to
ribosomes attached to the
outer surface of the
membranes
• Smooth endoplasmic
reticulum has no ribosomes
attached
Ribosomes
• Eucaryotic ribosomes are 18-22 in
diameter
• Clusters of ribosomes (polyribosomes
observed in mRNA
• It is composed of two subunits (60S
subunit)(40S subunit) these subunits
produced in nucleus, transported to the
cytoplasm and join together with
mRNA molecule to initiate protein
synthesis
• When 60S with 40S join together give
80S ribosome
• S is the sedimentation coefficient which
is the rate at which a particle or
molecule moves
• Most proteins produced are not mature
and need further processing in Golgi
complex
Golgi Complex
• It is known as Golgi
apparatus or Golgi
body
• It is connected to ER
• It completes the
transformation of
newly synthesized
proteins into mature
and functional ones
Lysosomes and Peroxisomes
Lysosomes:
• Small vesicles that originate at the Golgi complex
• Contain lysozyme and other digestive enzymes
• These enzymes breakdown foreign material taken
into the cell by phagocytosis
• Phagocytosis: engulfing of large particles by
amebas and certain types of white blood cells
(phagocytes)
• Lysosomes are found in all eukaryotic cells
Peroxisomes:
• Are membrane – bound vesicles
• It contain the enzyme catalase which catalyses
the breakdown of hydrogen peroxide to water
and oxygen
H2O2
Catalase
H2O + O2
• Are found in all eukaryotic cells especially in
mammalian liver cell
Mitochondria (single = mitochondrion)
• It is the “power plants”,
“powerhouses” or “energy
factory” of eukaryotic cell
• Why? Because most of ATP
molecules are formed by
cellular respiration by the
formation of high energy
ATP which is the major
carrying or energy storing
molecules
• Number of mitochondria
varies greatly depending on
the activities required of the
cell
Plastides
• It is another type of energy–producing
organelle
• They are membrane-bound structures
containing photosynthetic pigments
• They are the site of photosynthesis
• Chloroplast: is one type of plastide
contain green photosynthetic pigments
called chlorophyll, which found in
plant cells and algae
• Photosynthesis: is the process by
which light energy is used to convert
carbon dioxide and water into
carbohydrates and oxygen, the carbon
bond in carbohydrate is the stored
energy
H2O+CO2 Chlorophyll C6H12O6 + O2
• Light energy  chemical energy
Cell Wall
• Some eukaryotic cells contain cell
walls
• It is external structure that provide
rigidity, shape, and protection
• It may contain: cellulose, pectin,
lignin, chitin and some mineral salts
• Cell wall of algae contain
polysaccharide (cellulose) not found in
the cell wall of any other
microorganisms
• Cell wall of fungi contain
polysaccharide-chitin not found in the
cell walls of any other microorganisms
• Cell wall are present in algae, plants,
fungi, and most bacteria
• Cell wall are absent in animals,
protzoa and mycoplasma species
Flagella and Cilia
Flagella
• Some eukaryotic cells
possess long thin structures
called flagella=flagellum
• These cells are said to be
flagellated or motile
• It provide cell with
whipping motion enable
them swim through liquid
environment
• Flagella are organelles of
locomotion (cell mov.)
• Cells may possess 1,2 or
more flagella
Cilia (cilium)
• Are organelles of
locomotion
• But they are shorter (hair
like), thinner and more
numerous than flagellum
• Cilia can be found on
some species of protozoa
(ciliated) and on certain
types of our body
(epithelial cells in our
respiratory tract)
• The movement is tend to
be coordinated, rhythmic
Procaryotic Cell Structure
• Procaryotic cells are about 10 times
small than eukaryotic cell
• Procaryotic cells are very simple
cells compared to eukaryotic cells
• They reproduce by binary fission
which is defined as a simple
division of one cell into two cells,
following DNA replication and the
formation of a separating membrane
and cell wall
• All bacteria and archaens are
prokaryotes
• Within the cytoplasm are a
chromosome, ribosomes and other
cytoplasmic particles
• The cytoplasm is surrounded by a
cell membrane, a cell wall and
sometimes a capsule or a slime layer
all the above three called envelope
Cell Membrane (Plasma, Cytoplasmic, Cellular)
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Enclosing the cytoplasm of a prokaryotic cell
Similar in structure and function to the eukaryotic cell membrane
Plasma membrane consists of proteins and phospholipids
Selectively permeable to control which substances may enter or leave
the cell
Flexible and so thin that it cannot be seen with a compound light
microscope
Enzymes are attached to the cell membrane, and also a variety of
metabolic reactions
There are inward foldings called mesosomes, where cellular
respiration takes place in bacteria (same as mitochondria of
eukaryotes where nutrients are broken down to produce energy in the
form ATP)
In cyanobacteria and other photosynthetic bacteria contain infoldings
in the cell membrane contain chlorophyll and other pigments
Not contain endoplasmic reticulum, Golgi complex, membrane bound
organelles or vesicles
Chromosome
• Usually consist of a single long, supercoiled,
circular DNA which is the control center of the
bacterial cell, and capable of duplicating itself,
guiding cell division and directing cellular
activities
• Doesn’t contain nucleoplasm nor nuclear
membrane
• Chromosome is suspended or embedded in the
cytoplasm
• E.coli chromosome 1.5 mm long and 2 nm wide,
while E.coli is 2-3 µm long so the chromosome is
500-750 times longer than the cell itself
• Plasmid is a small circular molecules of double
stranded DNA and it is not part of chromosome
(extrachromosomal DNA or plasmid)
Cytoplasm
• It is semiliquid
• Consist of water, enzymes, dissolved oxygen, waste
products, essential nutrients, proteins, carbohydrates,
lipids
Cytoplasmic Particles
– Ribosomes
• Occurring in clusters called polyribosomes or
polysomes
• Procaryotic ribosomes are smaller than
eukaryotic ribosomes
• But they have the same function sites of protein
synthesis
• 70S prokaryotic ribosome composed of 30S
subunit and 50S subunit
Bacterial Cell Wall
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Rigid exterior cell wall
Defines the shape of bacterial cells
Its structure different from that of eukaryotic cell wall
It has the same function: providing rigidity, strength,
protection
The main constituents of bacterial cell walls is
peptidoglycan (murein layer)
This layer is only found in bacteria
Gram positive have thick murein layer
The genus Mycoplasma do not have cell wall
Archaeans have cell walls but its cell wall doesn’t contain
peptidoglycan
Gram positive cell wall structure
Gram negative cell wall structure
Glycocalyx (slime layers and capsules)
Glycocalyx
• A thick layer located outside their cell wall
• Slimy, gelatinous material produced by cell
membrane and secreted outside the cell wall
– Slime Layer:
• not highly organized
• not firmly attached to the cell wall
• It is easily detached from the cell wall
e.g: Pseudomonas (slime layer is the
cause of disease
Capsule:
– highly organized
– firmly attached to the cell wall
– consists usually of polysaccharides sometimes combined
with lipids and proteins
– we could differentiate between bacteria (to vaccine the
encapsulated bacteria)
– can be detected by negative stain
– Encapsulated bacteria usually produce colonies on
nutrient agar are smooth, mucoid, glistening known as S
colonies
– non capsulated dry, rough called R colonies
– capsule serve as antiphagocytic
Flagella (flagellum)
• Are Threadlike protein appendages that enable bacteria to
move
• Flagellated bacteria are said to be motile
• non flagellated bacteria are non motile
• bacterial flagella are about 10-20nm thick, too thin to be
seen under the microscope
• the number and arrangement of flagella are characteristic
to a certain species and can be used for classification and
identification:
– Peritrichous bacteria: bacteria
possessing flagella are over their entire
surface
– Lophotrichous bacteria: bacteria with a
tuft of flagella at one end
– Amphitrichous bacteria: bacteria having
one or more flagella at each end
– Monotrichous bacteria: bacteria
possessing a single polar flagellum
Structurally; bacterial flagella consist of
three, four or more threads of protein
called flagellin
Pili (Fimbriae) (sing. Pilus and Fimbria)
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Hair like structures
Often observed on Gram-negative bacteria
Composed of polymerized protein (pilin)
Pili are much thinner than flagella
Have a rigid structure and are not associated with
motility
• Arise from cytoplasm and extend through plasma
membrane, cell wall and capsule
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a. pilus: enables bacteria to adhere or attach to surfaces
b. Sex pilus: enables transfer of genetic material from one
bacterial cell to another
• Bacteria possess pili are able to cause disease
while if the same bacteria doesn’t have pili so
it cannot cause disease
• Bacterial cells possessing sex pilus (called
donor cell) while bacteria able to attach
(recipient bacteria)
• Conjugation to plasmid transfer is occur in the
presence of sex pilus
Spores (Endospores)
• Bacillus and Clostridium are capable of forming thickwalled spores
• Called endospores is produced by sporulation
• During sporulation, a copy of the chromosome and some of
the surrounding cytoplasm becomes enclosed in several
thick protein coats
• Spores are resistant to heat, drying and most chemicals
• Spores have been survive many years in soil or dust and
some are quite resistant to disinfectant and boiling
• When a dried spore lands on a moist, nutrient-rich surface it
germinate to a new vegetative cell
• Spore stain terminal and subterminal and central
• Sporulation is not a process of reproduction
Tyndallization
It is a sterilization technique which
successfully killed both heat labile
and heat stable forms, e.g. spore
former and non spore former
bacteria.
Reproduction of Organisms and their Cells
Reproduction: is the term in which organisms
reproduce.
Asexual Reproduction
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A single organism is the sole parent
It passes copies of all of its genes to its offspring
Some single-celled eukaryotes can reproduce by mitotic
cell division a process by which their chromosomes are
copied and allocated equally to two daughter cells
Sexual reproduction
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Two parents give rise to offspring that have unique combinations
of genes inherited from both parents
Miosis and fertilization is common to all organisms that reproduce
sexually
A zygote(fertilized egg) is formed by the fusion of gametes
Life Cycle: can be defined as the generation-to-generation
sequence of stages to occur in the reproductive history of an
organism
Human life cycle: production of haploid gametes by miosis----- fusion of gametes to produce a diploid zygote------mitotic division of the zygote to produce a multicellular
organism( haploid cells contain only one set of
chromosomes, while diploid cells contain two sets of
chromosomes
Eucaryotic Cell Reproduction
Mitosis:
– Refers to nuclear division which is the equal division of
one nucleus into two genetically identical nuclei
Meiosis:
– Diploid cells are changed into haploid cells
– Human diploid cells 46 chromosomes, whereas human
haploid cells (sperm cell and ova) contain 23
– Meiosis is the processes by which gametes are produced
Procaryotic Cell Reproduction
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Is quite simple when compared to eukaryotic cell division
It is reproduce by binary fission, where one cell (the
parent cell splits in half to become two daughter cells)
Before division, its chromosome must be duplicated so
each daughter cell will poccess the same genetic
information as the parent cell
The time it takes for binary fission to occur (the time it
takes for one prokaryotic cell to become two cells) is
called the generation time
The generation time varies from one bacterial species to
another and also depends on the growth condition (pH,
temperature, availability of nutrients) e.g E.coli have
generation time 20 minutes
Taxonomy
Is the science of classification, nomenclature and identification
1. Classification is the arrangement of organisms into taxonomic groups
Kingdoms------Divisions or Phyla-------Classes------Orders---------Families-----Genera-----Species
2. Nomenclature is the assignment of names to the various taxa according
to international rules (Binomial)
3. Identification is the process of determining whether an isolate belongs
to one taxa or unidentified species
Microbial Classification
– Categories of organisms into 5 kingdoms
• Kingdom Procaryote (Monera) Bacteria and
Archaeans
• Kingdom Protista(Protists) Algae and Protozoa
• Kingdom Fungi Fungi
• Kingdom Plantae Plants
• Kingdom Animalia Human and Animals
Viruses are not included because they are not living cells
(acellular)
Chapter 4
Diversity of
Microorganisms
Acellular and
Procaryotic Microbes
Acellular Infectious Agents
Viruses
The Main Characteristics of Viruses
• They Possess either DNA or RNA, unlike living cells which
possess both
• They are unable to replicate on their own: their replication is
directed by the viral nucleic acid once it is introduced into a
host cell
• Unlike cells, they do not divide by binary fission, mitosis, or
meiosis
• They lack the genes and enzymes necessary for energy
production
• They depend on the ribosomes, enzymes and metabolites
(building blocks) of the host cell for protein and nucleic acid
production
Classification of Viruses
Viruses are classified by the
following characteristics:
• Type of genetic material
(either DNA or RNA)
• Shape of the capsid
• Number of capsomeres
• Size of capsid
• Presence or absence of an
envelop
• Type of host that it infects
• Type of disease produced
• Target cell
• Immunologic preparation
Bacteriophages
Viruses that infect bacteria are known as
bacteriophage
•
•
Obligate intracellular pathogens.
It must enter a bacterial cell in order to
replicate
There are three categories
– Icosahedron bacteriophages:
spherical shape, 20 triagonal
faces, the smallest icosahedron
phage are 25 nm in diameter
– Filamentous bacteriophages: long
tube, formed by capsid proteins,
helical structure, 900 nm long
– Complex bacteriophage:
icosahedral heads attached to
helical tails
Types of Bacteriophade
• Virulent bacteriophage: always cause the
lytic cycle which ends the destruction
(lysis) of bacterial cell
• Temperate phages (lysogenic phages): Do
not immediately initiate the lytic cycle,
but their DNA remains integrated into the
bacterial cell chromosome, generation
after generation.
*Animal Viruses
• Infect humans and animals
• Some animal viruses are DNA and others are RNA viruses
• May consist of nucleic acid surrounded by protein coat or
be more complex.
*Latent Virus Infections
• Infected persons harbor the latent virus in nerve cells
• Fever, stress, or excessive sunlight can trigger the viral
genes to take over the cell and produce more viruses, and
cells destroyed.
*Antiviral
*Oncogenic Viruses:
Viruses that cause cancer
Human Immunodefficiency Viruses (HIV)
• Cause (AIDS)
acquired immune
deficiency
syndrome
• Envelop- double
stranded RNA virus
• Member of a genus
Lentiviruses, family
Retroviruses
• HIV destroy CD4
and helper T cell
(important cells in
the immune system(
*Viroids and Prions
• Viroids and prions smaller and less complex
infectious agents
• Viroids consist of short naked fragments of
SSRNA
• A viroids are transmitted between plants
• NB : A virion : is a complete viral particle
• Prions: are small infectious proteins that
cause fatal neurologic diseases in animals (
sheep, goats)
The Domain Bacteria
Atmospheric Requirements
• It is useful to classify bacteria on the
basis of their relationship to oxygen
and/or carbon dioxide
–
–
–
–
–
–
Obligate aerobes (20-21% oxygen)
Microaerophilic aerobes (microaerophiles)
Facultative anaerobes (0-20% oxygen)
Aerotolerant anaerobes
Obligate anaerobes
Capnophiles increased concentration of
CO2
Nutritional Requirements
• All bacteria need some form of the elements
C, H, O, S, P, N for growth
• Special elements K, Ca, Fe, Mn, Mg, Co, Cu,
Zn, are needed by certain bacteria
• Some microbes have specific vitamin
requirements
• Some microbes have specific organic
substances secreted by other living
microorganisms
• Fastidious organisms: organisms with
especially demanding nutritional
requirements
Pathogenicity
• The characteristics that enable bacteria
to cause disease
• Many pathogens are able to cause
disease because they possess capsules,
pili, or endotoxins, or secrete exotoxins
and exoenzymes that damage cells and
tissues
Unique Bacteria
• Rickettsias, Chlamydias, and Mycoplasmas are
Gram negative bacteria
• They do not possess all the attributes of typical
bacterial cell
• So small and difficult to isolate
• Formerly it is thought to be viruses
Rickettisias
–
–
They are Gram negative
Obligate intracellular pathogens that
cause disease in humans and other
animals
– To grow in vitro must be inoculated
into embryonated chicken eggs,
laboratory animals or cell cultures
– All diseases caused by Rickettisia
species are transmitted by arthropod
vector (carriers) transmit reckettisias
from one host to another (fleas, ticks)
and cause typhus and typhus-like
disease
Chlamydias
– It is called the “energy parasites”,
energy-storing or energy- carrying
molecules of the cells.
– Pathogens are transferred by inhalation
of aerobes or by direct contact, cause
trachoma (the leading cause of
blindness) as well conjunctivitis (eye
disease)
Mycoplasmas
– Are the smallest of the cellular microbes
– They lack cell walls, so they assume
many shapes from coccoid to
filamentous (pleomorphic) differ than
that L form (which lost the cell wall)
– Gram negative
– In human pathogenic mycoplasmas
cause atypical pneumonia and
genitourinary infections
– They are resistant to treatment with
penicillin
– They could be treated with tetracycline
Photosynthetic Bacteria
•
•
•
– Include purple bacteria, green, and cyanobacteria
– Use light as an energy source
– Some of them produce oxygen (oxygenic photosynthesis)
e.g cyanobacteria
– Some of them does not produce oxygen (anoxygenic
photosynthesis)
– In algae and plants photosynthesis takes place in plastids
– In cyanobacteria photosynthesis takes place in thylakoids
– Cyanobacteria are able for blooming
– Cyanobacteria are able for nitrogen fixation
– Some cyanobacteria produce toxin (poisons)such as:
Neurotoxins => affect the cental nervous system
Hepatotoxins => affect the liver
Cytotoxins => affect other types of cells
– Toxins are harmful to : birds, domestic animals, wild
animals, zooplankton
– Certain cyanobacterial toxins may contribute to cause
cancer
The Domain Archaea
• They were referred as archaebacteria
• Now it is known archae
• Ancient (thought it is developed earlier than
bacteria)
• Vary in shape (some cocci, some bacilli, some long
filaments)
• Extremophiles: they live in extreme environment
such as acidic, hot, salty, and extreme pressure
• Some live in the bottom of the ocean and near
thermal vents
• Other archaeans called methanogens which
produce methane
• Their cell wall has no peptidoglycan
Chapter 5
Diversity of Microorganisms
Eucaryotic Microbes
1.Algae (sing. Alga)
Characteristics and Classification
• Are photosynthetic, eukaryotic organism belong to
kingdom Protista
• All algal cells consist of cytoplasm, cell wall, cell
membrane, nucleus, plastids, ribosomes,
mitochondria and Golgi bodies
• Sometimes cells have pellicle (a thickened cell
membrane) and a stigma (eye spot), and/or flagella
• They are not plants
• Algae range in size from tiny, unicellular, microscopic
organisms to large multicellular plant like seaweeds
Medical Significance
• One genus of algae (Prototheca) cause human
infection which present in soil and enter the human
body through wounds in feet, it causes lesion, if the
organism reach the lymphatic system it may be fatal
especially to immunosuppressed individuals
• Algae in several other genera secrete substances
(phycotoxins)
• Phycotoxicoses (sing. Phycotoxicosis) are diseases
caused by phycotoxins, and they are example of
microbial intoxication
2. Protozoa(sing.Protozoan)
Characteristics
• Are eukaryotic organisms belong to kingdom Protista
• Most protozoa are unicellular, ranging in length 32000µm
• Are free living organisms
• Found in soil and water
• Protozoal cells are animal-like
• Protozoal cells possess cell membrane, nuclei,
endoplasmic reticulum, mitochondria, Golgi bodies,
lysosomes, centrioles and food vacuoles
• Some protozoa possess pellicles, cytosomes, contractile
vacuoles, pseudopodia, cilia and/or flagella
• Have no chlorophyll, cannot make their own food by
photosynthesis
• Some ingest algae, yeast, bacteria as nutrient
others live on dead or decaying organic matter
• Contractile vacuole: an organelle which pump
water out of the cell
• During life cycle 2 stages occur
– Trophozoite: is the motile, feeding, dividing
stage in protozoan’s life cycle
– Cyst is the dormant, survival stage (like
bacterial spore)
• Many protozoa are pathogens cause Malaria,
giardiasis, amebic dysentery
• Other protozoa have symbiotic relationship (e.g
Termite and intestinal protozoa digest wood)
Classification and Medical Significance
1. Sarcodina=>move by pseudopodia=>engulf and
the digestive enzymes released from lysosomes
(as well white blood cells)
Medically-----Entamoeba histolytica-----cause
amebic dysentery, amebiasis and extraintestinal
amebic abscesses
2. Mastigophora
Trypanosoma transmitted by the tsetse fly, causes
African sleeping sickness in humans
3. Ciliophora
Paramecium transmitted to human via drinking
water has been contaminated by swine feces
and cause dysentery
4. Sporozoea
Plasmodium transmitted by female Anopheles
mosquitoes which become infected when they
take a blood meal from a person of Malaria
• NB Affect badly on immunosuppressed
persons
Fungi (sing. Fungus)
•
•
•
•
Characteristics
Belong to the kingdom fungi
Cell wall made of chitin
Many fungi are unicellular(yeast)
others are filaments
hyphae(sing.hypha) which form
mycelium (plural mycelia)
Some filamentous fungi are septate
and some others are aseptate hyphae
Reproduction
•
Fungal cells can reproduce by
budding, hyphal extension, or the
formation of spores.
N.B: Pseudohyphae: String of elongated
bud
•
There are two general categories of
fungal spores: sexual spores and
asexual spores
•
Sexual spores produced by the fusion
of gametes
Classification
See Book
Medical Significance
• Mycotoxicoses (sing. Mycotoxicosis)
– Mycotoxins: are complex metabolites that are harmful to
humans and animals
– Mycotoxins symptoms may include vomiting, diarrhea,
thirst, hallucination, high fever, gangarene of the limbs
and death
– Aflatoxin is a kind of mycotoxin, it is carcinogenic
(cancer causing), ingestion of aflatoxin cause liver
damage and hepatic cancer
– Some fungi produce only a single mycotoxin or more
– Mycotoxicoses: Common in domestic animals than
humans because animal ingest fungal-contaminated foods
Fungal Infections of Humans
Fungal infections are known as mycoses (sing.mycosis)
Categories of fungal infection
• Superficial and cutaneous mycoses
– Fungal infection of the outermost area of the human body e.g:
hair, fingernails, toenails and the dead outermost layers of the
skin
• Cutaneous mycoses
– Fungal infections of the living layers of the skin(the dermis) e.g:
tinea infections, Candida albicans(opportunistic pathogens)
• Subcutaneous and systemic mycoses
They are more severe types of mycoses
• Subcutaneous: fungal infections of the dermis and underlying
tissues e.g: Madura foot
• Systemic: fungal infections of internal organs,2 or more
different organs e.g: spores in the respiratory system by
inhaling
Mycoses are treated with antifungal agents
like nystatin, these chemotherapeutic agents
may be toxic to humans, they are prescribed
with due consideration and caution
Fleshy Fungi
Mashrooms are Fleshy fungi that
belong to Basidiomycetes
phylum
Dimorphic Fungi
• A few fungi, including some
human pathogens, can live
either as yeasts or as molds
depending on growth
conditions this phenomenon is
called dimorphism
• grown in vitro at body
temperature(37oC)---unicellular
yeast
• grown in vivo in human body----exist as yeast
• grown in vitro at room
temperature(25oC)---as molds
(mycelium) cause disease
Lichens
• They appear as colored, circular patches on
tree trunks and rocks
• Lichen are combination of two organisms an
algae and a fungus close to each other as
symbiotic relationships
Slime Molds
• Are found in soil and on rotting
• Have both characteristics of both fungal and
protozoa
• It start out in life as independent amebae
ingesting bacteria and fungi by phagocytosis
• When run out of food they fuse together to
form a motile, multicellular form, then it
becomes fruiting body contain spore which is
able to grow to amebae