Characteristics of
Microorganisms
-Bacteria
-Viruses
-Prions
-Fungi
-Protozoa
Next to Cover:
•biological molecules
•taxonomy
•nomenclature
•Basic Microbe Character
Genetic Material
DNA
•Chromosome
-how the DNA is
•Gene
-the small segment of DNA
that makes
Lipids
(Fats)
•Functions of Lipids
-cell membrane structure
-energy (storage)
-protection (cushion)
Protein
•Functions of Protein
-work (action)
-structure
-cell recognition
-energy
Fluid Mosaic Model
•Model of
carbohydrates
lipids
protein
Carbohydrates
(sugars)
•Functions of Carbs
-energy
-structure
-cell recognition
Microorganisms
Acellular
Cellular
Prokaryotes Eukaryotes
Animal cells
Plant cells
Fungi
Protozoa
Major Similarities Between
Prokaryotes and Eukaryotes
•
•
in cell
throughout
cell
•
is the genetic
material
• cell (plasma)
membrane
Major Differences Between
Prokaryotes
and
• no
•
chromosome
Eukaryotes
• contains a
• multiple
• no
• contains organelles
• complex
• simple or no cell
wall
• smaller
• larger
Taxonomy
Categorizing Living Organisms
The 5 Kingdoms
• In 1969, Robert Whittaker proposes
organizing all organisms into Kingdoms
plants,
algae
mushrooms,
molds, yeast
vertebrates,
insects
protozoa,
slime molds
The 3 Domains
•In 1970s, Carl Woese proposes 3 domain
system
Classifying Human Beings
Domain
subspecies,
strains,
varieties
Binomial Nomenclature
• Genus: 2 or more species with similar
• Species: groups of organisms with
similar
- for microbes, 70% genetic similarity
- for plants / animals, same species
can breed
Binomial Nomenclature
How you write the name
Homo sapiens
Escherichia coli
Escherichia
Genus - first letter
Species - all lower case
Both words underlined or in italics
Abbreviated Forms
Escherichia coli
E. coli
Streptococcus pneumoniae S. pneumoniae
Viruses named differently
e.g. AIDS virus Human Immunodeficiency
Virus (HIV)
Other Name Designations
• Strains
• microbes within a species with
some genetic change, e.g.
• E. coli O157:H7
Microbial Size
How Small Is Small?
Units of Measure
• micrometer (µm) is a unit of
measurement
• 1 millimeter (mm) =
micrometers (µm)
• 1 millimeter (mm) =
nanometers (nm)
• typical size of a
human being = 1.6 m
m > mm > µm > nm
• typical size of a
bacterium = 1 to 5 µm • typical size of a
virus = 50 to 250 nm
Microscopes
Compound Light
Microscope
Magnification =
100 – 1000 X
(single cells)
Electron Microscope
Magnification
over 20 million X
( articles)
Two forms of electron microscopy:
1. Scanning electron microscopy (SEM)
2. Transmission electron microscopy (TEM)
Fluorescence Microscopy
• used to positively identify any specific microbe
Application: bacterial or viral identification
-microbe-specific antibody + fluorescent ‘tagged’
antibody
-antibodies added to unknown microbe, then washed
• microbe exposed to
UV light
Microbe
Fluorescence Microscopy
Application: bacterial or viral identification
- ‘positive’ microbes fluoresce under UV light
Classification leads to….
• Identification
• Identifying characteristics
•
•
•
•
•
•
•
•
•
•
cell morphology
staining reactions
motility
colony morphology
atmospheric requirements
nutritional requirements
biochemical & metabolic activities
specific enzymes
pathogenicity
genetic composition
Bacterial Morphology
• Refers to
• cell shape & arrangement
• rod-shaped
•
(pl. bacilli)
• spherical or round
•
(pl. cocci)
• curved or wavy
• curved rod • rigid wave -
• flexible wave -
(pl. spirilla)
Bacterial Morphology
Other Arrangements
Strepto
Cocci
• pairs
• diplococcus
• chain
• Strepto
• grape-like cluster
• Staphylo
s
Staining Techniques
• used to help visualize
bacteria
• used to help identify
bacteria
• used to help
differentiate different
kinds of bacteria
3 Major Staining Techniques
1) Simple Stain:
-stains all bacteria same colour
2) Gram Stain:
-differentiates type of cell wall
3) Acid-fast Stain:
-identifies
Common to all Staining:
• place a small
drop of bacterial
sample on slide
(smear)
• heat fix the
sample
bacteria
to slide
Simple Stain
• a basic (+ve) dye stains all bacteria
-crystal violet is most common
• water washes away access stain
The Gram Stain
Gram ve
Gram
ve
Gram Stain
Grambacterium
Grambacterium
So, what’s the difference?
Gram +ve
protein / carbohydrate
Lipids / protein
cell wall
cell membrane
Gram -ve
outer membrane
cell membrane
cell wall
Lipids / protein
protein / carbohydrate
Lipids / protein
So, who cares?
Staphylococcus aureus
Gram ve bacteria
• susceptible to
Escherichia coli
Gram ve bacteria
• susceptible to
• releases
from
outer membrane
Gram
Acid-Fast Stain
• similar to Gram stain (2 stains used), except:
1) Red stain is used first
2) Heat is used to help first stain penetrate
3) Acid / alcohol is used to wash the first stain
4) Blue stain stains all other cells for contrast
Waxy cell wall
eg.
cell wall
cell membrane
Lung biopsy subjected to Acid-Fast Stain
Bacterial
Envelope
Glycocalyx
Cell wall
Cell membrane
Glycocalyx
• Sticky layer of polysaccharide & small
proteins
• Roles of glycocalyx:
• Only certain bacteria
- in many rods and spheres, not in spiral
Example of Bacteria with Glycocalyx
haemophilus influenzae
• causes
• difficult for
to
penetrate glycocalyx
• death rate in treated
meningitis =
%
• if thick and tightly
bound, called a ‘
’
• if thin and flowing,
called a ‘
’
• if thin and flowing,
called a ‘
layer’
Example:
Pseudomonas aeruginosa
• opportunistic bacteria
• causes
and lung infections
• colonies of glycocalyx-covered bacteria can
come together to form ‘
’
• this film makes colonies difficult to kill
Bacterial Cell Wall
• Complex, semi-rigid structure
• Responsible for
• Protects against
pressure
changes
• Composition and thickness varies
e.g. Gram positive vs Gram negative
Gram ve
cell wall
cell membrane
Cell wall =
protein +
carbohydrate
(
)
acid
What is Teichoic acid?
• a component of Gram +ve cell walls
• made of phosphate and alcohol
• high
•
charge
outer membrane
Lipopolysaccharide
-
Gram
region
ve
cell wall
cell membrane
Key Differences Gram +ve / Gram -ve
Gram +ve
Gram –ve
•Thicker
•Thinner
peptidoglycan
peptidoglycan
•No outer membrane •Outer membrane
-periplasmic region
•Teichoic acid
•LPS
Cytoplasmic Contents
• Gelatinous liquid containing…
• ribosomes
• inclusion bodies
• single chromosome
• plasmids
What are plasmids?
• small circular pieces
of bacterial
.
•
essential for life
• carries
resistance
• acts as ‘emergency’
genetic material
Bacterial Endospores
•
/resistant stage of certain
bacterial cells
•
a form of reproduction
• Formed when moisture or nutrient
supply low
• Spores are extremely resistant and
live for long periods of time
Spore coat =
Some diseases caused
by Sporeformers:
• anthrax
• tetanus
• gas gangrene
• botulism
Bacterial Appendages
Flagella
• Long, thread-like appendages present
in some bacteria
• Allow bacteria to move (motility)
• Each flagellum is made of rigid
protein subunits called
• Filament rotates at about 600 rpm
(10 rotations per second)
• Bacteria can move at 50 µm/s
• Bacteria move by ‘
’
- attracted to favourable conditions,
repelled from unfavourable
• Clockwise = tumble
• Counterclockwise = run
• Unfavourable = long tumbles, short runs
• Favourable = short tumbles, long runs
Pili
• Many, short, hair-like appendages
• Like flagella, pili are made of protein (
• Help bacteria to:
•
to other bacteria & surfaces
•
genetic material to another
bacterial cell
)
What do Pili do?
1) Attach bacteria to surfaces or other cells
-‘
’
2) Transfer DNA from one bacterium to another
-‘
pili’
This process is called ‘
’
Flagella versus Pili
Flagella
Pili
Made of flagellin
Made of pilin
Longer (10-20 µm) Shorter (0.5 – 2 µm)
Used for mobility
Used for:
-attachment
-conjugation
Bacterial Reproduction
•
complex
process than
mitosis
Generation (doubling) time
•
Measurement of Bacterial Growth
• Reproduce usually at a rapid rate
• Usually between 20 minutes to 30
hours
• Generation (doubling) time
• time, in minutes, for a population
to double
•
or logarithmic growth
Starting with one E. coli
• in 1hr, 8 bacteria
• in 3 hrs, 512 bacteria
• in 10 hrs, 1 billion bacteria
• in 36 hrs,
covered!
Note: y axis is logarithmic
Note: y axis
is linear
Growth Requirements
• Temperature
•
grow best between
•

C
• pH
• usually grow best between
• pH
• psychrophile grows at 0 – 20 oC
oC
• mesophile grows at
• thermophile grows at 40 – 90 oC
Oxygen Requirements
• some bacteria breath oxygen (aerobes)
• some bacteria don’t (anaerobes)
• oxygen is an excellent energyconverting molecule
However
• oxygen generates oxygen free
radicals (toxic)
• aerobic bacteria must break down free
radicals, or die
Oxygen Requirements (con’t)
Classifications
• obligate
require
eg.
• obligate
eg.
:
for life
:
grow in oxygen (it’s toxic)
Oxygen Requirements
Classifications (con’t)
• facultative anaerobes / aerobes:
can
oxygen
eg.
• microaerophiles:
require
of oxygen
(too much is toxic)
eg. Mucus bacteria
cause oral / digestive disease
Patterns of Nutrition
• Bacteria need water and food
Where do they get it from?
1) They make it themselves:
autotrophs
2) They eat it:
heterotrophs
a)
: eat dead organisms
b)
: eat live organisms
(pathogens cause disease)
Bacterial Cultivation
• We grow bacteria in broth or agar
Agar:
-polysaccharide from marine red
algae
- provides ‘semi-solid’ surface
for bacterial growth
-nutrients added (agar not
)
Agar powder added to nutrients
Heated (above 85 OC)
to dissolve agar
Liquid agar poured;
solidifies below 36 OC
Types of Nutrient Agar (broth)
1. Complex Media
Includes: beef extract,
peptone, sodium
chloride
most bacteria
Types of Nutrient Agar (broth)
2. Selective Media
Example: high salt agar
( % instead of 0.5%)
grow well
Types of Nutrient Agar (broth)
3. Differential Media
Example:
agar
Staphylococcus aureus / epidermidis
versus
Streptococcus pyogenes
Types of Nutrient Agar (broth)
Combined Selective and
Differential
Example:
agar
Staphylococcus epidermidis
versus
Staphylococcus aureus
Measuring Bacterial Cell Number
1. Turbidity
- cell count based on light scatter
Measuring Bacterial Cell Number
2. Direct Microscope Count
Measuring Bacterial Cell Number
3. Standard Plate Method
- determines CFUs
Isolating Pure Culture
1) Streak plate method
2) Pour plate method
1) Streak plate method
2) Pour plate method