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Transcript
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
4
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
5
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.
6
7
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
8
9
Fig 4.10
10
Cytoplasmic membrane
Protoplast
Spheroplast
L forms
11
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
12
Gram positive
Gram negative
13
Gram positive
Gram negative
14
Fig 4.16
Lipopolysaccharide
n
O-antigen
Highly variable
Core
• Heptoses
• Ketodeoxyoctonic acid
Lipid A
• Glucosamine disaccharide
• Beta hydroxy fatty acids
(Hydroxy myritic Acid)
15
LPS function
Endotoxins
Exotoxins
16
Gram positive wall
17
Gram negative cell wall
18
Peptidoglycan
19
Lipoteichoic acid
Peptidoglycan-teichoic acid
Cytoplasmic membrane
Cytoplasm
Porin
Outer Membrane
Lipopolysaccharide
lipoprotein
Inner (cytoplasmic) membrane
Cytoplasm
20
Gram Positive Cell Envelope
Lipoteichoic
acid
r
Peptidoglycan-teichoic acid
r
r
r
r
r
r
r
r
r
Cytoplasmic membrane
Cytoplasm
21
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)
22
2 Types of Glycocalyx
23
Biofilms
24
Flagella
25
Monotrichous
lophotrichous
amphitrichous
26
peritrichous
Fig 4.2b
27
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
29
Conjugation
30
endospores
31
Important components in
endospore:
Calcium
Dipicolinic Acid
32
Sporulation
The endospore
34
35
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
36
Grwth in Bacteria
•
•
•
•
Temperature
Nutrients
pH
Osmotic pressure
37
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
38
3 temperature adaptation groups
39
Bacterial Metabolism
• Phototroph
o Photoautotroph (Photolitotroph)
o Photoheterotroph (Photoorganotroph)
• Chemotroph
o Chemoautotroph (Chemolitotroph
o Chemoheterotroph (Chemoorganotroph)
40
Stages of metabolism in
chemoheterotrophic bacteria
• Digestion
• Absorption (Passive and active
transportation)
• Preparation for oxidation
• Oxidation
41
Oxygen requirements
42
43
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
44
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
49
Bacterial Colonies
• Standard Bacterial Count
• Colony-Forming Units
• Plaque-Forming Units
•Spread Plate
• Pour Plate
• Soft-Agar Overlay
Solid Medium
52
53