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Ch 4 Cell Structure
- 1. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
CHAPTER 4
AN INTRODUCTION TO CELL STRUCTURE AND
HOST-PATHOGEN RELATIONSHIPS
- 2. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
WHY IS THIS IMPORTANT?
You have to understand cell structure for
success in studying microbiology in general
and the process of infection in particular
Understanding the relationship between host
cells and pathogens is required for
understanding the processes of infection and
disease
- 4. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
CLASSIFICATION OF
ORGANISMS
All living organisms can be classified as either:
Prokaryotes – lack membrane-bound organelles
Eukaryotes – contain membrane-bound organelles
- 5. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
CLASSIFICATION OF
ORGANISMS
Biologists classify microorganisms by their genus
name and their species name
An example is Clostridium tetani. Clostridium is the
genus and tetani is the species
In some cases, the genus can have several species.
An example is Clostridium tetani and Clostridium
botulinum
The genus and species names of microorganisms
are italicized when written
- 6. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
BACTERIA: Overview
Bacteria are the smallest living organisms and
are microscopic
Bacteria are immensely diverse and very
successful organisms that colonize all parts of
the world and its inhabitants
- 7. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
BACTERIA: Size, Shape, and
Multicell Arrangement
Bacteria can be of different shapes, sizes, and
arrangements
The most common shapes are:
Bacillus (rod-shaped)
Coccus (spherical)
Spiral (spiral-shaped)
- 8. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
BACTERIA: Size, Shape, and
Multicell Arrangement
- 9. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
BACTERIA: Size, Shape, and
Multicell Arrangement
- 10. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
BACTERIA: Size, Shape, and
Multicell Arrangement
- 11. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
BACTERIA: Size, Shape, and
Multicell Arrangement
Panel b: © CDC/ Dr. Richard Facklam; Panel c: © CDC/ Dr. Mike Miller
- 12. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
BACTERIA: Size, Shape, and
Multicell Arrangement
Panel b: Macmillan Publishers, Ltd: Review in Microbiology, Volume 2, Issue 6, © (2004).; Panel c: © CDC
- 13. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
BACTERIA: Size, Shape, and
Multicell Arrangement
Panel b: © CDC/ Janice Haney Carr/ Jeff Hageman, M.H.S.;Panel c: © CDC/ Dr. Thomas F. Sellers/Emory University
- 14. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
BACTERIAL STAINING:
Types of Stain
Bacteria can be stained in the following ways:
Simple stains – stain using only one color
Differential stains – stain using more than one
color
- 15. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
THE GRAM STAIN
The Gram stain takes advantage of the
differences in the cell walls of bacteria
The Gram stain process divides bacteria into
four major groups:
Gram-positive
Gram-negative
Gram-variable
Gram nonreactive
- 17. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
THE NEGATIVE (CAPSULE)
STAIN
The negative technique stains the background
surrounding encapsulated bacteria
It can be used to identify the presence of a
capsule (important in virulence factors) as the
background staining makes the capsule highly
visible
- 18. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
THE NEGATIVE STAIN
© CDC/ Courtesy of Larry Stauffer, Oregon State Public Health Laboratory
- 19. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
THE FLAGELLA STAIN
The flagella stain identifies the presence of
flagella, which are used for motility
Motility is important for infection as it allows
the invading organisms to move from the
initial site of infection
- 20. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
THE FLAGELLA STAIN
© CDC/ Dr. William A. Clark
- 21. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
THE ZIEHL-NEELSEN
ACID-FAST STAIN
This stain is used to detect Mycobacterium
species such as M. tuberculosis (the cause of
tuberculosis) or M. leprae (the cause of
leprosy)
These organisms have mycolic acid (a
virulence factor) in their cell walls, making the
cell wall difficult to penetrate
- 22. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
THE ZIEHL-NEELSEN
ACID-FAST STAIN
It uses heat as part of the process to permit the
entry of the stain
It is called acid-fast because positive cells
retain color even after washing with acid
- 23. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
THE ZIEHL-NEELSEN
ACID-FAST STAIN
© CDC/ Dr. George P. Kubica
- 24. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
THE ENDOSPORE STAIN
Endospores are small, tough, dormant
structures that can form in certain bacteria
Heat is needed to make the endospore wall
permeable to the stain
- 25. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
THE ENDOSPORE STAIN
© CDC/ Courtesy of Larry Stauffer, Oregon State Public Health Laboratory
- 26. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
HOST-PATHOGEN
RELATIONSHIPS
Infectious diseases have been major causes of
death and suffering throughout history
Pathogens are organisms that cause infectious
diseases
- 27. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
HOST-PATHOGEN
RELATIONSHIPS
Infectious diseases are complex and involve a
series of shifting interactions between host and
pathogen
For the pathogen, the interactions depend on:
The pathogen’s ability to evade or overcome the
host’s defense
The pathogen’s ability to increase in numbers
The pathogen’s ability to identify transmission
mechanisms to new hosts
- 28. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
HOST-PATHOGEN
RELATIONSHIPS
For the host, the interactions depend on:
The host having useful functioning defenses
The host’s susceptibility to infection
The degree of compromise found within the host
immune system
- 29. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
PATHOGENICITY
In most cases, the interactions between the
body and microbes cause no harm
Some microbes have a mutualistic relationship
with the host
In these cases, the microbes provide something
beneficial to us and we provide something
beneficial to them
However, some harmless organisms can
become opportunistically pathogenic
- 30. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
OPPORTUNISTIC PATHOGENS
AND PRIMARY PATHOGENS
Opportunistic pathogens cause infection by
taking advantage of a host’s increased
susceptibility of infection
Primary pathogens are those that cause disease
in healthy individuals
- 31. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
OPPORTUNISTIC PATHOGENS
AND PRIMARY PATHOGENS
Characteristics of primary pathogens are as
follows:
They have evolved mechanisms that can overcome
host defenses
Once inside, they can multiply rapidly
Some primary pathogens are restricted to humans
- 32. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
DISEASE AND
TRANSMISSIBILITY
Successful infection requires the following
from a pathogen:
The ability to multiply in sufficient numbers
The ability to transmit to new hosts
- 33. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
DISEASE AND
TRANSMISSIBILITY
Pathogens can be transmissible through:
Coughing – transmits respiratory infections
Diarrhea – transmits digestive infections
Infections that kill too quickly inhibit
transmission
- 34. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
BACTERIAL PATHOGENICITY
AND VIRULENCE
Pathogens must be able to accomplish the five
requirements for infection:
Entry (getting in)
Establishment (staying in)
Defeat the host defenses
Damage the host
Be transmissible
- 35. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
BACTERIAL PATHOGENICITY
AND VIRULENCE
Virulence refers to how harmful a pathogen is
to the host
Virulence depends on genetic factors of the
pathogen
These genes are often turned on only in the host
- 36. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
BACTERIAL PATHOGENICITY
AND VIRULENCE
Pathogens carry virulence genes in clusters
called pathogenicity islands
These can be located on plasmids
Plasmids can be transferred between cells
- 37. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
QUORUM SENSING
Organisms sense their environment using
special sensing proteins. This is called quorum
sensing
This sensing is based on population densities
Certain genes are only turned on when there
are enough cells present:
An example of this is toxin production in
Salmonella
- 38. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
BIOFILMS
Bacteria can grow in aggregated assemblies
within their host. These assemblies are called
biofilms
Biofilms are clinically important because:
They can capture and retain nutrients (allowing
continued growth)
They impede uptake of antibiotics and
disinfectants
They inhibit phagocytosis
- 39. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
BIOFILMS
Biofilms can build up on medical devices such
as:
Catheters
Internal pacemakers
Prosthetic devices
Biofilms are one of the causes of plaque build-
up on teeth
- 41. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
THE HOST CELL
There are several differences between
prokaryotic and eukaryotic cells
Many of the structures of eukaryotic cells play
a role in infection
- 44. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
The Plasma Membrane
The eukaryotic plasma membrane is made up
of a phospholipid bilayer
It is a fluid matrix containing a variety of
proteins and other molecules
- 45. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
The Plasma Membrane
- 46. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
Role of the Plasma Membrane in Infection
Because the plasma membrane is the barrier
between the inside and the outside of the cell,
it must be breached if pathogens are to gain
entrance
It contains specific receptors used by viruses
to attach to host cells
It can become the envelope for certain types of
viruses
- 47. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
Role of the Plasma Membrane in Infection
- 48. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
Cytoplasm
The eukaryotic cytoplasm consists of:
A semifluid material that is mainly water and
dissolved substances
Membrane-bound structures called organelles
Structures not bound by membranes
- 49. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
Role of the Cytoplasm in Infection
Cytoplasm is involved in a variety of
infections
It has a major role in viral infections
Many viruses replicate in the host cell
cytoplasm
- 50. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
Host Cell Cytoskeleton
The cytoskeleton gives eukaryotic cells
structural integrity
The cytoskeleton is involved in how cells are
joined together to form tissue
The components of the cytoskeleton play a
role in cellular mitosis and meiosis
- 51. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
Host Cell Cytoskeleton
There are three types of cytoskeleton
components:
Microfilaments
Intermediate filaments
Microtubules
- 52. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
Role of the Cytoskeleton in Infection
Many pathogens use the cytoskeleton as part
of the infection process
Shigella use microfilaments to move laterally
between cells of the intestine
- 53. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
Role of the Cytoskeleton in Infection
- 54. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
Cilia
Cilia are made up of microtubules that can be
projected outward from the cell surface
The lower respiratory tract is lined with
ciliated cells that help move trapped particles
upward and out of the respiratory tract
- 55. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
Role of Cilia in Infection
Pathogens can attack the cilia and destroy their
trapping capability
In some respiratory diseases, such as pertussis
(whooping cough), the pathogens (in this case
Bordetella pertussis) attach to host ciliated
cells as an initial part of the infection
- 56. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
Role of Cilia in Infection
© NIBSC / Science Photo Library
- 57. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
Ribosomes
Ribosomes are the site of protein synthesis
They are found either free in the cytoplasm or
attached to the endoplasmic reticulum
Ribosomes in eukaryotic cells have a different
structure to those prokaryotic cells
- 58. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
Role of the Ribosome in Infection
Eukaryotic ribosomes are very important in
viral infections:
The virus takes over the host cell ribosome
function
It is then used only to make new virus
- 59. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
Role of the Ribosome in Infection
Prokaryotic ribosomes are damaged by the
antibiotics erythromycin and streptomycin
Eukaryotic ribosomes are not affected by these
antibiotics
- 60. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
Mitochondria
Mitochondria produce ATP in eukaryotes
Mitochondria are very similar to bacteria
Bacterial prokaryotes integrated into
eukaryotic cells as mitochondria – part of the
endosymbiotic theory
- 61. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
ER & Golgi Apparatus
Both systems of membranes that form
flattened sacs and platelike structures
The endoplasmic reticulum (ER) can be
smooth (without ribosomes) for lipid
synthesis, or rough (with attached ribosomes)
for protein synthesis
- 62. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
ER & Golgi Apparatus
The Golgi apparatus has the three following
functions:
Modifying and packaging products coming from
the ER
Renewing the cell’s plasma membrane
Producing lysosomes
- 63. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS: Role of the
ER & Golgi Apparatus in Infection
Both structures are involved in the
biosynthesis and assembly of viruses
The ER is also involved in the adaptive
immune response to infection
- 64. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
Lysosomes
Lysosomes are filled with destructive enzymes
and chemicals
They create vesicles
They are responsible for destroying pathogens
that enter the cell
They also act in recycling host cell
components
- 65. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
Proteasomes
Proteasomes are organelles that participate in
the degradation of proteins
They are also involved in recycling protein
components
- 66. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
Role of the Proteasome in Infection
Proteosomes degrade the proteins of
pathogenic cells
The degraded proteins trigger an immune
response against the pathogen
- 67. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
Peroxisomes
Peroxisomes are organelles that participate in
the degradation of fatty acids
They contain catalase, and enzyme that
counteracts hydrogen peroxide–a
by-product of fatty acid break down
- 68. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
The Nucleus
The nucleus is the location of the cellular DNA
of eukaryotic cells
The nucleus is bound by a double
phospholipid bilayer membrane
It is the site for DNA replication during cell
division
The transcription of messenger RNA also
occurs here
- 69. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
Role of the Nucleus in Infection
The nucleus of the host cell is important in
many infections, particularly those caused by
DNA viruses
Copies of the viral DNA are made in the nucleus
These copies are then moved into the cytoplasm to
be used for the construction of new virus
molecules
- 70. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
Endocytosis & Exocytosis
Endocytosis involves bringing things into the
cell through the formation of vesicles
Exocytosis involves moving things out of the
cell which is also done through the formation
of vesicles
- 71. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
Endocytosis & Exocytosis
There are three ways that endocytosis operates
within a cell:
Pinocytosis
Phagocytosis
Receptor-mediated endocytosis
- 72. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS:
Endocytosis & Exocytosis
- 73. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS: Role of
Endocytosis & Exocytosis in Infection
Many pathogens enter the host cell through the
formation of vesicles
This method provides protection for the
pathogen from the host immune response
Some pathogens bind to host cell receptors
that trigger endocytosis. This is particularly
true of viruses
- 74. ISBN: 978-0-8153-6514-3Microbiology: A Clinical Approach, by Tony Srelkauskas © Garland ScienceMicrobiology: A Clinical Approach (2nd
Edition) © Garland Science
EUKARYOTIC CELLS: Role of
Endocytosis & Exocytosis in Infection
Phagocytosis is a type of endocytosis that can
be used to defend against infection
Many pathogens have found ways to defeat
phagocytosis