Plants, like most animals, are
multicellular eukaryotes
Archaea
Eubacteria
Fungi
Animals
Plants
Protists
Common ancestors
Photo credits: Public Health Image Library;
NASA; © Dave Powell, USDA Forest
Service; tom donald
EUKARYOTES
PROKARYOTES
BACTERIA ARCHAEA
2
Prokaryotes (Bacteria)
• Eubacter "True" bacteria
– human and plant pathogens
– clinical or environmental
– one kingdom
• Archaea
– Environmental organisms
– second kingdom
3
Prokaryotic Cell (versus Eukaryotic
Cell)
•
•
•
•
Not compartmentalized
Cell membranes lack sterols (e.g. cholesterol)
Single circular chromosome
Ribosomal are 70S
- subunits
•
•
30S (16S rRNA)
50S (5S & 23S rRNA)
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Bacteria versus Archaebacteria
• Eubacteria
– peptidoglycan (murein)
– muramic acid
• Archaebacteria
– pseudomurein
– no muramic acid
• 16S rRNA
– sequence different
5
Morphology
• Shape
– cocci (round)
– bacilli (rods)
– spiral or curved (e.g. spirochetes)
• Single or multiple cells
– clusters (e.g. staphylococci)
– chains (e.g. streptococci)
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Bacterial requirements for growth
•
•
•
•
•
oxygen (or absence)
energy
nutrients
optimal temperature
optimal pH
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Obligate aerobes
• grow in presence of oxygen
• no fermentation
• oxidative phosphorylation
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Obligate anaerobes
•
•
•
•
no oxidative phosphorylation
fermentation
killed by oxygen
lack certain enzymes:
superoxide dismutase
O2-+2H+
H2O2
catalase
H2O2
H20 + O2
peroxidase
H2O2 + NADH + H+
2H20 +
NAD
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Aerotolerant anaerobes
• respire anaerobically
• not killed by oxygen
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Facultative anaerobes
• fermentation
• aerobic respiration
• survive in oxygen
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Microaerophilic bacteria
• grow
– low oxygen
• killed
– high oxygen
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Nutrient Requirements
•
•
•
•
•
Carbon
Nitrogen
Phosphorus
Sulfur
Metal ions (e.g. iron)
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Measuring bacterial mass (live + dead)
in liquid culture
Turbidity
(Cloudiness)
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Measuring viable bacteria
Colony forming units
colony
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Growth Curve
Stationary
COLONY
FORMING
UNITS
Death
Log
Lag
TIME
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Growth Curve
Stationary
TURBIDITY
(cloudiness)
Autolysis
Log
Lag
TIME
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Generation time
• time for bacterial mass to double
• Example
100 bacteria present at time 0
If generation time is 2 hr
After 8 hr mass = 100 x 24
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Eukaryotic cell
(e.g. animal)
Rough endoplasmic
reticulum
Nucleus
Gram +
Prokaryotic cell
Nucleoid/
Flagellum
nucleoid region
Cell membrane
Cell wall
Gram Pili
Cytoplasm
Mitochondria
Capsule
Granule
Cell (inner) membrane
Outer membrane
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Ribosomes
Cell wall
Plasmids
• Extra-chromosomal DNA
• multiple copy number
• coding
- pathogenesis factors
- antibiotic resistance factors
• bacterial replication
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The Cell Envelope
• Cell membrane + cell wall (+ plus outer
membrane)
• Cell wall
– peptidoglycan
– attached structures
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Oxidative phosphorylation occurs at cell membrane
(since there are no mitochondria).
Cell Wall
Cytoplasm
Cell membrane
The cell wall is outside of cell membrane
– rigid, protecting cell from osmotic lysis & some antibiotics.
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Gram Positive
Gram Negative
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GRAM POSITIVE
Lipoteichoic acid
Peptidoglycan-teichoic acid
Cytoplasmic membrane
Cytoplasm
GRAM NEGATIVE
Lipopolysaccharide
Porin
Outer Membrane
Braun lipoprotein
Inner (cytoplasmic) membrane
Cytoplasm
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Peptidoglycan
• single macromolecule
• highly cross-linked
• surrounds cell
• provides rigidity
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Peptidoglycan
• glycan backbone
– muramic acid
– glucosamine
• peptide side chain
• peptide cross-bridge
– D- and L- amino acids
– diaminopimelic acid
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Muramic acid, D-amino acids
diaminopimelic acid
– not synthesized by mammals
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L-alanine
D-glutamic acid
L-lysine/Diaminopimelic acid
D-alanine
D-alanine
Peptidoglycan
Muramic acid
Glucosamine
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GRAM POSITIVE
CELL ENVELOPE
Degradative enzyme
Lipoteichoic acid
Peptidoglycan-teichoic acid
Cytoplasmic membrane
Cytoplasm
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Gram Positive Cell
Envelope
•
Teichoic acid
– polymer
– ribitol phosphate or ribitol glycerol
backbone
–
• Teichuronic acid
– polymer
– no phosphorus
– glucuronic acid
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Teichoic and teichuronic acids
• Metal ion uptake
• Direct autolytic enzymes
– holes punched in cell wall
– allows insertion cell wall (synthesis)
31
Lipoteichoic acids
• cell membrane
• autolysins kept from cell wall
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GRAM NEGATIVE
CELL ENVELOPE
Outer Membrane
(Major permeability barrier)
Porin
Lipopolysaccharide
Braun lipoprotein
Degradative enzyme
Inner (cytoplasmic) membrane
Periplasmic binding protein
Cytoplasm
Permease
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Gram Negative
Peptidoglycan
• Braun lipoprotein
– binds cell wall to outer membrane
34
Outer Membrane
• lipopolysaccharide
• phospholipids
• Proteins
– porins
35
Outer Membrane
Gram negative bacteria
• major permeability barrier
• space between inner and outer membrane
– periplasmic space
store degradative enzymes
Gram positive bacteria
• no periplasmic space
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Lipopolysaccharide
• synthesis similar to peptidoglycan
• also on undecaprenol carrier
37
Lipopolysaccharide
n
O-antigen
Highly variable
Core
• Heptoses
• Ketodeoxyoctonic acid
Lipid A
• Glucosamine disaccharide
• Beta hydroxy fatty acids
38
FLAGELLA
•
•
•
•
Some bacteria are motile
Locomotory organelles- flagella
Taste environment
Respond to food/poison
– chemotaxis
39
• Flagella
–
–
–
–
embedded in cell membrane
project as strand
Flagellin (protein) subunits
move cell by propeller like action
A: monotrichous
B: Lophotrichous
C: Amphitrichous
D: Petritrichous
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Pili (fimbriae)
• hair-like projections of the cell
• sexual conjugation
• adhesion to host epithelium
41
Capsules and slime layers
•
•
•
•
•
•
outside cell envelope
well defined: capsule
not defined: slime layer or glycocalyx
usually polysaccharide
often lost during in vitro culture
protective in vivo
42
Endospores (spores)
• Dormant cell
• Produced when starved
• Resistant to adverse conditions
- high temperatures
- organic solvents
• contain calcium dipicolinate
• Bacillus and Clostridium
43
Koch's postulates
• isolated
– diseased not healthy organisms
• growth
– pure culture
• induce disease
– susceptible organisms
• re-isolated
– susceptible organisms
44