1 bio265 introduction to microbiology_dr di bonaventura_instructor
TRANSCRIPT
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Bio 265 lecture
Suggested
Textbook
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Antoni van Leeuwenhoek-Dutch
The Early Years of Microbiology - Late 1600s
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Reproduction of Leeuwenhoek’s microscope
Specimen holder Lens Antoni van
Leeuwenhoek
Changed the way
we see our world
Began making and
using microscopes
Examined water
and observed tiny
“animalcules”
The Early Years of Microbiology
By the end of the 19th century, “animalcules” were called
microorganisms (microbes)
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The Debate over Spontaneous Generation
Spontaneous generation: The hypothesis that living
organisms arise from nonliving matter
Biogenesis: The hypothesis that living organisms arise
from preexisting life
mid-1800s
Louis Pasteur
conducted experiments
that demonstrated the
theory of biogenesis
The Golden Age of Microbiology
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Steam escapes from open end of flask.
Infusion is heated.
Infusion sits; no microbes appear.
Months
Air moves in and out of flask.
Infusion remains sterile indefinitely.
Dust from air settles in bend.
When the “swan-necked” flasks remained upright, no microbial
growth appeared
When the flasks were tilted and the liquid touched the dust in their
necks, these flasks became cloudy with microbes
Pasteur’s Experiments
The Golden Age of Microbiology
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The Germ Theory of Disease
Late 1800s
Robert Koch proved that a
bacterium caused anthrax
Provided the experimental
steps, known as “Koch’s
postulates”
To demonstrate that a specific
microbe causes a specific
disease
The Golden Age of Microbiology
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The Golden Age of Microbiology
Koch’s Postulates
“Suspected causative agent” must be found in every case of the disease and be absent from healthy hosts
“Agent” must be isolated and grown outside the host
When the “agent” is introduced into a healthy host, the host must get the disease
Same “agent” must be found in the diseased experimental host
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Koch isolated rod-shaped
bacteria (Bacillus anthracis)
in the blood of cattle that had
died of anthrax
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Isolation of bacteria on solid media and the concept of
pure culture
Bacterium 1
Bacterium 2
Bacterium 3
Bacterium 4
Bacterium 5
Bacterium 6 Bacterium 7
Bacterium 8
Bacterium 9
Bacterium 10
Bacterium 11
Bacterium 12
Koch received the Nobel prize in 1905 after his publications on
the cause of tuberculosis – Mycobacterium tuberculosis
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The Golden Age of Microbiology
Gram’s Stain – 1884
Danish scientist Hans Christian Gram developed a staining technique
Involves the applications of a series of dyes
Some microbes are left purple, called Gram-positive
Other microbes are left pink, called Gram-negative
Gram staining
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What are the organisms
studied by microbiologists?
Prokaryotes Bacteria Archaea
Eukaryotes
Fungi Protozoa Algae Helminths
Eukaryotic-human cheek cells
Prokaryotic-bacterial cells
Viruses (too small to be seen with a simple microscope!)
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Unicellular organisms
Lack a nucleus
Reproduce asexually
Include:
Bacteria*
Cell walls contain peptidoglycan
Archaea
Cell walls lack peptidoglycan
Often found in extreme environments
Not known to cause disease in humans
Prokaryotes: Bacteria and Archaea
Haemophilus influenzae
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Prokaryotes - Bacteria
Proteus vulgaris
Vibrio cholerae
Staphylococcus aureus
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Prokaryotes - Bacteria
Escherichia coli
Borrelia burgdorferi
Streptococcus pneumoniae
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Eukaryotic (have membrane-bound nucleus)
Obtain food from other organisms
Possess cell walls
Molds are multicellular, grow as long filaments, and reproduce by sexual and asexual spores
Yeasts are unicellular, reproduce by budding, fission, or sexual spores
Fungi
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Penicillium chrysogenum Saccharomyces cerevisiae
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The discovery of antibiotics - 1929
Alexander Fleming
discovered the first
antibiotic
He observed that
Penicillium fungus made
an antibiotic (penicillin)
that killed S. aureus
Penicillin was tested
clinically and mass
produced
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Effects of penicillin on a bacterial “lawn” in a petri
dish
Fungus colony (Penicillium)
Zone of inhibition
Bacterial colonies (Staphylococcus)
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Disc impregnated with antibiotics are placed onto inoculated
plates
The clear zone around a disc indicates that bacterial growth
has been affected (bacterial cell are inhibited or killed)
Understanding the role of antibiotics
You will learn more
about this method
in the lab
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Single-celled eukaryotes
Similar to animals in nutrient needs and cellular structure
Live freely in water; some live in animal hosts as parasites
Asexual (most) and sexual reproduction
Capable of locomotion by
Pseudopodia
Cilia
Flagella
Protozoa
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Trypanosoma gambiense
Giardia lamblia
Protozoa
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Parasitic worms
Taenia: tapeworm
Most of these worms are not
microscopic as adult
Microscopic eggs and immature
stages can be found in blood, fecal,
and urine samples
Ascaris lumbricoides
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Viruses infecting a
bacterial cell
Viruses
Viruses are acellular parasites
Replicate only when they are
within a living host cell
Can be seen with an electron
microscope (1932)
Can infect
plants
animals (human body included)
bacteria (bacteriophages)
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The system of nomenclature for organisms currently in use
was established by C. Linnaeus, Swedish botanist, ~ 1753
Organisms have Latin names
Binomial nomenclature assigns each organism two names
Genus (genera) is the first name and it is capitalized
Species name follows and it is not capitalized
Both names are italicized (italics)
Esherichia coli
E. coli
Nomenclature (binomial nomenclature)
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Principles of Taxonomy
Organisms are grouped into a series of categories (taxa) that make up the taxonomic hierarchy:
A particular species belongs to a given genus, family, order,
class, phylum, … domain
Domain Kingdom Phylum Class Order Family Genus Species
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Taxonomic levels of the bacterium Shigella
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The three Domains of life - based on comparative analysis
of the nucleotide sequences of ribosomal RNA (rRNA)
The domain bacteria includes all of the pathogenic prokaryotes
3.5 billion years ago
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How do we distinguish and identify
different bacteria (prokaryotes)?
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Using Phenotype to Identify Prokaryotes
Colony morphology/appearance
Red pigment of Serratia marcescens
“Fried egg” appearance
of Mycoplasma colonies
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Microscopic analysis
Important initial step in the process of identification
Size
Shape (morphology)
Staining characteristics
Gram stain differentiate Gram positive/negative
Acid-fast stain
Special stains
Presence/absence of certain cell structures such
as flagella and endospores
Using Phenotype to Identify Prokaryotes
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Sputum
Male urethra
secretions
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Culture characteristics
Escherichia coli
EMB medium
MacConkey
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Haemophilus influenzae
Culture characteristics
Chocolate agar plate
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Staphylococcus aureus Culture characteristics
MSA medium
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Using Phenotype
to Identify Prokaryotes
Biochemical tests
Laboratory technicians
use biochemical tests to identify pathogens
Tests rely on pH
Indicators/addition of reagents ….
Commercial
biochemical tests allow for series of tests with a single inoculation
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Serology
Based on specific interaction between antibodies/surface
molecules, allows for rapid detection of numerous organisms
Using Phenotype to Identify Prokaryotes
Streptococcus pyogenes
is the causative agent of
strep throat
Target molecules are
carbohydrates of the cell
wall
Agglutination test-overview
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5 volumes
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CASE STUDIES FROM DAILY LIFE
The following case studies illustrate how microbiology is part
of our everyday lives:
Special Delivery
Ivan Goes to Chicago
Hamburger Havoc…..
The Hospital Can Be Dangerous!
Did You Wash Your Hands?
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Special Delivery (2001)
Letters contaminated
with a fine white
powder
Spores of Bacillus
anthracis
Gram stain of B. anthracis
Cause inhalation anthrax – A form of
pneumonia that can lead to respiratory
failure and death
B. anthracis is a potential weapon of
bioterrorism
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Ivan Goes to Chicago
Ivan has contracted multi-drug
resistant tuberculosis
(Mycobacterium tuberculosis)
He travels from Russia - through
NY (JFK) - to Chicago
On the plane he experiences severe
coughing spasms because he has
active disease
Acid fast stain of
Mycobacterium
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He goes to the
county hospital for
treatment
In the waiting room
he begins to cough
He is expelling
infectious
M. tuberculosis
In the hospital people may be debilitated from being ill or
immunocompromised
Ivan Goes to Chicago
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Hamburger Havoc…
You bring your daughter to her
favourite hamburger restaurant
Your daughter experiences:
diarrhea
vomit
severe abdominal cramping
her stool has blood in it
The doctor finds her anemic and in renal failure (she is put on
dialysis)
The child has been infected by enterohemorrhagic bacteria called
Escherichia coli found in improperly processed ground meat
Escherichia coli
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The hospital can be dangerous!
Uncle Harry went to the hospital for a hip operation
The operation went well but when you go to the hospital to bring
uncle Harry home
You find that he has been
transferred to intensive care in a
room with a sign outside that
reads: MRSA Authorized
Personnel Only
Uncle Harry has contracted a
nosocomial infection (hospital-
acquired) and dies few days later S. aureus is associated with
nosocomial pneumonia
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MRSA:
Methicillin-resistant
Staphylococcus
aureus
VRSA:
Vancomycin-resistant
Staphylococcus
aureus
Thousands of people die each year in US from nosocomial infections
(increase in antibiotic resistance among bacteria)
Intensive care
The hospital can be dangerous
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Did You Wash Your Hands?
1800s, an hospital in Vienna, in which thousands of children
were born each year
Puerperal fever (childbed fever) caused by b-hemolytic
streptococcus killed hundreds of mothers each year
In the wing where these deaths were most prevalent, only
doctors and medical students delivered babies
The battle of Dr. I. Semmelweis
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Dr I. Semmelweis figured out that
doctors and medical students had directly moved from performing
autopsies to the delivery room without properly washing their
hands
SEM - Chains of streptococci
Did You Wash Your Hands?
When they began to wash
their hands thoroughly with
chlorinated lime water
The number of deaths
caused by this infection
dropped to about 1%
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Why is microbiology relevant to health care?
Infectious disease accounts for a large percentage of health
care
New diseases are appearing (emerging diseases)
Diseases we thought were eradicated are reappearing (re-
emerging diseases)
Resistance to antibiotics that were effective is increasing
The potential for bioterrorism has become fact
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Not all microorganisms are pathogens!
Only a tiny fraction of microorganisms (bacteria, viruses,
fungi, parasites) out of thousands of species cause disease
Many bacteria and some fungi are part of the normal
microbiota of our body, which colonize skin and mucosal
surfaces
Most of the time these organisms are harmless and in some
cases they provide us with benefits
We use microbes to produce antibiotics, food, beverages (beer
and wine)!
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