Download Gram positive Gram negative

Bacterial Cell Structure
Fig. 4.1
1
Cytoplasm
• dense gelatinous solution of sugars, amino
acids, & salts
• 70-80% water
• serves as solvent for materials used in all
cell functions
2
Chromosome
• single, circular, double-stranded DNA
molecule that contains all the genetic
information required by a cell
• DNA is tightly coiled around a protein,
aggregated in a dense area called the
nucleoid
3
DNA temperature melting
Bacteria classification
A +T
G+C
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plasmids
•
•
•
•
•
small circular, double-stranded DNA
free or integrated into the chromosome
duplicated and passed on to offspring
not essential to bacterial growth & metabolism
may encode antibiotic resistance, tolerance to
toxic metals, enzymes & toxins
• used in genetic engineering- readily manipulated
& transferred from cell to cell
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Ribosomes
• made of 60% ribosomal RNA & 40%
protein
• consist of 2 subunits: large & small
• procaryotic differ from eucaryotic
ribosomes in size & number of proteins
• site of protein synthesis
• All cells have ribosomes.
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Inclusions, granules
• intracellular storage bodies
• vary in size, number & content
• bacterial cell can use them when
environmental sources are depleted
• Examples: glycogen, poly-b-hydroxybutyrate,
gas vesicles for floating, sulfur and
polyphosphate granules
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Fig 4.10
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Cytoplasmic membrane
Protoplast
Spheroplast
L forms
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4 groups based on cell wall
composition
1.
2.
3.
4.
Gram positive cells
Gram negative cells
Bacteria without cell walls
Bacteria with chemically unique cell walls
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Gram positive
Gram negative
13
Gram positive
Gram negative
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Fig 4.16
Lipopolysaccharide
n
O-antigen
Highly variable
Core
• Heptoses
• Ketodeoxyoctonic acid
Lipid A
• Glucosamine disaccharide
• Beta hydroxy fatty acids
(Hydroxy myritic Acid)
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LPS function
Endotoxins
Exotoxins
16
Gram positive wall
17
Gram negative cell wall
18
Peptidoglycan
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Lipoteichoic acid
Peptidoglycan-teichoic acid
Cytoplasmic membrane
Cytoplasm
Porin
Outer Membrane
Lipopolysaccharide
lipoprotein
Inner (cytoplasmic) membrane
Cytoplasm
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Gram Positive Cell Envelope
Lipoteichoic
acid
r
Peptidoglycan-teichoic acid
r
r
r
r
r
r
r
r
r
Cytoplasmic membrane
Cytoplasm
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Glycocalyx
•
•
Coating of molecules external to the cell wall,
made of sugars and/or proteins
2 types
1. capsule - highly organized, tightly attached
2. slime layer - loosely organized and attached
•
Functions
–
–
–
attachment
inhibits killing by white blood cells
Receptor (K antigen)
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2 Types of Glycocalyx
23
Biofilms
24
Flagella
25
Monotrichous
lophotrichous
amphitrichous
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peritrichous
Fig 4.2b
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Fimbrae
• Adhesion to other cells and surfaces
28
pili
• rigid tubular structure made of pilin protein
• found only in Gram negative cells
• Functions
– joins bacterial cells for DNA transfer (conjugation)
– adhesion
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Conjugation
30
endospores
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Important components in
endospore:
Calcium
Dipicolinic Acid
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Sporulation
The endospore
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Major Taxonomic Groups of
Bacteria
• Gracilicutes – gram-negative cell walls,
thin-skinned
• Firmicutes – gram-positive cell walls, thick
skinned
• Tenericutes – lack a cell wall & are soft
• Mendosicutes – archaea, primitive
procaryotes with unusual cell walls &
nutritional habits
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Grwth in Bacteria
•
•
•
•
Temperature
Nutrients
pH
Osmotic pressure
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Temperature
• Minimum temperature – lowest
temperature that permits a microbe’s growth
and metabolism
• Maximum temperature – highest
temperature that permits a microbe’s growth
and metabolism
• Optimum temperature – promotes the
fastest rate of growth and metabolism
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3 temperature adaptation groups
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Bacterial Metabolism
• Phototroph
o Photoautotroph (Photolitotroph)
o Photoheterotroph (Photoorganotroph)
• Chemotroph
o Chemoautotroph (Chemolitotroph
o Chemoheterotroph (Chemoorganotroph)
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Stages of metabolism in
chemoheterotrophic bacteria
• Digestion
• Absorption (Passive and active
transportation)
• Preparation for oxidation
• Oxidation
41
Oxygen requirements
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Fermentation
• Incomplete oxidation of glucose or other
carbohydrates in the absence of oxygen
• Uses organic compounds as terminal electron
acceptors
• Yields a small amount of ATP
• Production of ethyl alcohol by yeasts acting on
glucose
• Formation of acid, gas & other products by the
action of various bacteria on pyruvic acid
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Fermentation
45
Binary division
46
Growth Curve
Continuous Culture, Chemostat
Chemostats are a
means of keeping a
culture in log phase
indefinitely.
Methods in bacterial
identification
1.
2.
3.
4.
5.
6.
Microscopic morphology
Macroscopic morphology – colony appearance
Physiological / biochemical characteristics
Chemical analysis
Serological analysis
Genetic & molecular analysis
•
•
•
G + C base composition
DNA analysis using genetic probes
Nucleic acid sequencing & rRNA analysis
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Bacterial Colonies
• Standard Bacterial Count
• Colony-Forming Units
• Plaque-Forming Units
•Spread Plate
• Pour Plate
• Soft-Agar Overlay
Solid Medium
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