1 basic characters of bacteria
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Basic Characters of Bacteria
Hope Tan
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Size and ShapesSize and Shapes Size:Size:
Unit for measurement Unit for measurement ::
Micron or Micron or micrometer, μm: 1μm=10micrometer, μm: 1μm=10-3-3mmmm
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coccus bacillus Spiral
bacterium
Basic shapes of batcteriaBasic shapes of batcteria
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Cocci: sphere, 1μm
Bacilli: rods , 0.5 ~ 1 μm in width, 1~3 μm
in length
Spiral bacteria: 1~3 μm in length and 0.3~
0.6 μm in width
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CoccusCoccus
S. Pneumoniae N. gonorrhoeae Streptococci
Tetrads Sarcina Staphylococcus
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Bacillus
S. typhi B. abortus C. diphtheriae
C. Botulinum M. tuberculosis B. anthracis
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Spirillum
Vibrio
Spiral bacterium
V. cholerae
H. pylori
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Basic structures Cell wall Cell membrane Cytoplasm Nuclear materialSpecial structures Capsule Spore Flagella Pili
Structure of bacteriaStructure of bacteria
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Basic structure of bacteriaBasic structure of bacteria
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1. Chemical composition :
A. Common component—— peptidoglycan
Also called mucopeptide or glycopeptide or murein
Cell wallCell wall
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• A backbone of N-acetyl glucosamine and N- A backbone of N-acetyl glucosamine and N-
acetyl muramic acid: Both discovered in acetyl muramic acid: Both discovered in
GG++and Gand G-- bacteria. bacteria.• A set of identical tetrapeptide side chain A set of identical tetrapeptide side chain
attached to N-acetyl-muramic acid: different attached to N-acetyl-muramic acid: different
components and binding modes in Gcomponents and binding modes in G++and Gand G--
bacteria.bacteria.• A set of identical peptide cross bridges: only A set of identical peptide cross bridges: only
in Gin G++bacteriabacteria
peptidoglycan
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N – acetyl-gulcosamine
N – acetyl-muramic acidβ-1,4 glucosidic bond
① Polysaccharide backbone
PeptidoglycanPeptidoglycan
STRUCTURESTRUCTURE ::
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② Tetrapeptide side chain
③ Peptide cross-bridges
Bond to N – acetyl-muramic acid
Bond to Tetrapeptide side chain and only found in GG+ + bacteria
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peptidoglycan for peptidoglycan for GG+ + bacteriabacteria
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peptidoglycan for peptidoglycan for GG--bacteriabacteria
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Diaminopimelic acid
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Function and medical significance of peptidoglycanFunction and medical significance of peptidoglycan ::
① ① Constructure of tenacious cell wall architectureConstructure of tenacious cell wall architecture
Gram positive bacteria—Gram positive bacteria—threethree-dimensional structure-dimensional structure
Gram negative bacteria—Gram negative bacteria— two two-dimensional structure-dimensional structure
② ② Target of some antibioticsTarget of some antibiotics :: For exampleFor example :: Penicilin can inhibit the binding between tetrapeptide
side chain and peptide cross-bridges, while lysozyme can
hydrolyze the β-1,4 glucosidic bond
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Penicilin
Lysozyme
Reactive site of some antibiotics in peptidoglycan
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Cell wallCell wall
1. 1. Chemical composition :: A. A. Common component—— peptidoglycan
B. Special componentB. Special component
Gram positive bacteria——teichoic acid Gram positive bacteria——teichoic acid
Special surface proteinsSpecial surface proteins
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Teichoic acidTeichoic acid
Structure:
Chemical composition
phosphodiester bondRibitol residue
Glycerine residue
Ribitol type
Polymerizer
Glycerine type
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Classfication
According to bonding site on the bacteria,
teichoic acid can be classified into two types
Membrane teichoic acid,
also called lipoteichoic acid (LTA)
Wall teichoic acid
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teichoic acidteichoic acid
Membrane teichoic acid
Wall teichoic acid
Peptidoglycan
Teichoicacid
Cellwall
Phospholipid
ProteinCell membrane
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Function and medical significance of teichoic Function and medical significance of teichoic acidacid ::
① Bearing a strong negative charge.
② Adhesive attraction, relating to pathogenicity
③ They are strongly antigenic, helpful to identify
and type a bacterium
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cell wall for cell wall for GG+ + bacteriabacteria
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Cell wallCell wall
1. 1. Chemical composition :: A. A. Common component—— peptidoglycan
B. Special componentB. Special component
Gram positive bacteria——teichoic acidGram positive bacteria——teichoic acid
Special surface proteins Special surface proteins
Gram negative bacteria——outer membraneGram negative bacteria——outer membrane
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Outer membraneOuter membraneStructure
Lipopolysaccharide
lipid bilayer
Lipoprotein
Outer membrane
Cell membrane
Periplasmic space
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Lipid A
Core polysaccharide
Specific polysaccharide
(O- polysaccharide)
LPSendotoxin
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① ① Adsorption and excretionAdsorption and excretion
② ② Barrier function
③ ③ Pathogenicity
④ ④ AntigenicityAntigenicity
⑤ ⑤ Receptor: F pilusReceptor: F pilus, phage, bacteriocin
Function and medical significance of Function and medical significance of outer membraneouter membrane ::
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Cell wall for Cell wall for GG- - bacteriabacteria
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Comparison of cell wall between Gram negative Comparison of cell wall between Gram negative and Gram positive bacteriaand Gram positive bacteria
Characters G+ G-
Strength Tenacious Curmbly
Thickness Thick , 20 ~ 80nm Thin , 5 ~ 10nm
Layers of peptidoglycan More , about 50 layers Few , 1 ~ 3
layers
Content of peptidoglycan High , 50 ~ 80% of cell
wall dry weight
Little , 10 ~ 20%
of cell wall dry
weight
Structure of peptidoglycan Three-dimensional Two-dimensional
Content of carbohydrate About 45% 15-20%
Teichoic acid + -
Outer membrane - +
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Structures and compositions of cell wall
G + bacterium
Peptidoglycan-rich cell wall
G+ bacterium cell wall
--Peptidoglycan
-- Teichoic acid
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Structures and compositions of cell wall
G - bacterium cell wall
--Peptidoglycan
--Outer membrane Lipoprotein
Lipid bilayer
LPS
Lipid-rich
cell wall
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• Countering the effects of high intracellular osmotic Countering the effects of high intracellular osmotic
pressure and maintaining the cell’s characteristic pressure and maintaining the cell’s characteristic
shapeshape• Barrier and protection• Participate in substance exchange of bacterial cellParticipate in substance exchange of bacterial cell
Function and medical significance of cell wall
• Determinate some important characters of bacteria Determinate some important characters of bacteria
pathogenicitypathogenicity
immunogenicityimmunogenicity
antibiotics sensitivity
chromaticity : Differentiate bacteria: G + / G
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2. Wall-less forms of BacteriaWall-less forms of Bacteria (bacteria L form)
Causes: lysozyme, penicilin, antibody, complements,
macrophage, neutrophile granulocyte, bile, UV, etc.
Definition : bacteria that the cell wall was impaired
but maintain the competence of growth and cell
division
L form of Gram positive bacteria —— protoplast
L form of Gram negative bacteria —— spheroplast
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Characteristics :
• Appearance : polymorph
• Chromaticity : Gram negative
• Characteristic of cultivate : hyperosmotic
pressure, low concentrated agar with
serum,
and it grows very slow
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Causes :
•Lysozyme, penicillin, antibody, complements,
macropages, neutropile granulocyte, bile, UV,
etc.
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Colony
Fried egg type colony
Granular type colony
Filamentous type colony
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Fried egg (L) type
Granular (G) type
Filamentous (F) type
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• Reversion: L-form bacteria can revert to its
normal bacteria when the cause was removed at the
early time of formation, the determinant condition is
whether there is peptidoglycan remaining in the cell
wall. And if it is subcultivated for many times in
vitro, it can never be reverted.
•Pathogenicity : L-form bacteria bearing virulence
( diagnosis )• Antibiotic sensitivity : changed ( cure )
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Basic structure Cell wall Cell membrane Cytoplasm Nuclear materialSpecial structure Capsule Spore Flagella Pili
Structure of bacteriaStructure of bacteria
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No cholesterol
Important sturctures:
Cell membraneCell membrane
MesosomesMesosomes Mesosomes are specialized structures formed by
retractable, folded and curled cytoplasmic membrane,
and divided into septal and lateral mesosome. also
called chondroid.
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MesosomesMesosomes
Penecillin-binding proteins, (PBP )
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Function
•Material transportation
•Respiration
• Biosynthesis :
Penicillin-binding protein
• Participate in cell division : mesosome
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Basic structures Cell wall Cell membrane Cytoplasm Nuclear materialSpecial structures Capsule Spore Flagella Pili
Structure of bacteria
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Ribosomes: numerous,
15 - 20nm in diameter with
70S; distributed throughout
the cytoplasm; site of protein
synthesis ;sensitive to
streptomycin and
erythromycin
CytoplasmCytoplasm
Composed largely of water, together with proteins,
nucleic acid, lipids and small amount of sugars and salts
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Plasmids: extrachromosomal genetic elements
Plasmids are small, circular , extra-
chromosomal , double-stranded DNA
molecules. They are capable of self-replication
and contain genes that confer some important
properties, such as antibiotic
resistance , virulence factors. Plasmids are not
essential for cellular survival.
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Inclusions: sources of stored energy, e,g volutin
Inclusions are aggregates of various compounds
that are normally involved in storing energy reserves
or building blocks for the cell.
Inclusions accumilate
when a cell is grown in
the presence of excess
nutrients and they are
often observed under
laboratory conditions.
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Basic structures Cell wall Cell membrane Cytoplasm Nuclear materialSpecial structures Capsule Spore Flagella Pili
Structure of bacteria
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Lacking nuclear membrane, absence of
nucleoli, hence known as nucleic material
or nucleoid, one to several per bacterium.
Nuclear material
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Special structure of bacteria
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Basic structures Cell wall Cell membrane Cytoplasm Nuclear materialSpecial structures Capsule Spore Flagella Pili
Structure of bacteria
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CapsulesCapsules
These are structures surrounding the outside of the cell wall.
They are not essential to cell
viability and some strains within a
species will produce a capsule, whilst
others do not. Capsules are often
produce in vivo or on a eutrophic
medium and lost during in vitro
culture.
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• Antigenicity – Composition: polysaccharide
• Pathogenicity – Protection from phagocyte
– Resistance to drying – Adherence
Function and medical significance
Formation condition
In vivo or eutrophic
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Basic structures Cell wall Cell membrane Cytoplasm Nuclear materialSpecial structures Capsule Spore Flagella Pili
Structure of bacteria
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FlagellaFlagella
• Some bacterial species are mobile and possess
locomotory organelles - flagella. Flagella consist of
a number of proteins including flagellin
•The diameter of a flagellum is thin, 20 nm, and long
with some having a length 10 times the diameter of
cell. Due to their small diameter, flagella cannot be
seen in the light microscope unless a special stain is
applied. Bacteria can have one or more flagella
arranged in clumps or spread all over the cell.
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Classification According to the number and distribution of Flagella, Flagella,
Flagella bacteria can Flagella bacteria can be classified into four types:
Monotrichate
Lophotrichate
Amphitrichate
Peritrichate
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• Motility
• Pathogenicity – e.g., Vibrio cholerae
• Antigenicity – protein
– also called as H Ag
Function and significance
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Basic structures Cell wall Cell membrane Cytoplasm Nuclear materialSpecial structures Capsule Spore Flagella Pilus
Structure of bacteria
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Pili are hair-like
projections of the cell ,
They are known to be
receptors for certain
bacterial viruses.
Chemical nature is pilin
Pilus
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Classification:
Ordinary pili or fimbriae: fine, rigid
numerous, related to bacterial adhesion
Sex pili: longer and coarser, only 1-4,
related to bacterial conjugation
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Function:
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Basic structures Cell wall Cell membrane Cytoplasm Nuclear materialSpecial structures Capsule Spore Flagella Pili
Structure of bacteria
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a thickwalled form produced in a bacterial cell. It is very resistant to being killed by heat and various other chemical and physical agents.
Spore
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Formation and germination
In vitro or malnutrition
In vivo or eutrophic
Bacteria (vegetative form)
spore ( only one )
Bacteria (vegetative form, also only one)
Form conditions
(Dormant cell)(Dormant cell)
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Multiple layers of resistant coats
Dipicolinic acid or calcium dipicolinate
Low content of water
• Contains a complete nucleus material, ribosomes
and energy-generating components
• Highly resistant to heat, dessication, and chemicals
Reasons
High-pressure steam sterilization is the most effective way to kill the spores
Characteristics:
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Coats of sporeCoats of spore
Spore coat
Exosporium
SporewallCore Cortex
Endomembrane
Exomembrane
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Medical significance
• Identification of a bacteria: size, appearance
and site
• Standard of sterilization
•Important source of infection —— anthrax,
tetanus, etc.
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Bacterial Metabolism and MultiplicationBacterial Metabolism and Multiplication
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Bacterial MetabolismBacterial Metabolism
Energy Metabolism Energy Metabolism
Important Metabolic ProductsImportant Metabolic Products
1. Catabolic processes1. Catabolic processes
2. Anabolic processes2. Anabolic processes
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Products of anabolic processes and its Products of anabolic processes and its medical significancemedical significance
Pyrogen: a fever-producing substance mainly
synthesized by gram negative bacteria, it is highly
resistant to heat and it has the property of
pyrogenicity. It is a very important microbial
contamination evaluation index of biological products.
Toxins and Invasive Enzymes: Toxins: endotoxin, exotoxin
Invasive Enzymes: hyaluronidase, streptokinase,
streptodornase, and so on.
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Pigments Classification—lipo solubility, water solubility
Observation the pigments is helpful to the
identification of a bacteria.
Antibiotics
Substance produced by some microbes
and bearing the property of inhibition or
killing effect to some other microbe or
tumor cells.
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Bactericin
Substances produced by some strains of
bacteria and bearing the antibacterial activity to
the bacteria that related to bactericin-produce
one.
Vitamins
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The medical significance of these products?
Medical significance
Pathogenicity of bacteria
Treatment of infectious diseases
Identification of bacteria
Products
Pyrogen
Toxin
Invasive enzyme
Antibiotic
Vitamin
Bacteriocin
Pigment
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Requirments for Bacteria GrowthRequirments for Bacteria Growth
1. Nutrients: 2. Temperature 3. Hydrogen ion concentration ( pH ) 4. Oxygen Requirements5. Osmotic pressure
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1.NutritionNutrition
Factors affecting bacterial growth and division Nutritive material:: Water Carbon source Nitrogen source Minerals Growth factors etc.etc.
Requirments for Bacteria GrowthRequirments for Bacteria Growth
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2. Temperature2. Temperature
The temperature suitable for most bacteria growth is
from 20 to 40 centigrade, but the most appropriate
temperature for cultivation of pathogenic bacteria is 37
centigrade.
• Psychrophilic forms( 15-20 )• Mesophilic forms ( 30-37 ): Include all human
pathogens and opportunists.
• Thermophilic forms ( 50-60 )
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3. hydrogen ion concentrationhydrogen ion concentration ( pH )
The pH value that fit for most bacteria growth is The pH value that fit for most bacteria growth is
from 7.2 to 7.6, but some bacteria grow well in from 7.2 to 7.6, but some bacteria grow well in acidity
environment, while some bacteria just at the opposite.environment, while some bacteria just at the opposite.
According to the appropriate pH value, bacteria
can be classified into three groups just as follows:
• Neutrophiles( 5 to 8)
• Acidophiles( below 5.5)
• Alkaliphiles( above 8.5)
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•obligate aerobeobligate aerobe
•microaerophilic bacteriummicroaerophilic bacterium
•facultative anaerobefacultative anaerobe
• obligate anaerobeobligate anaerobe
According to the oxygen requirement,
bacteria can be classified into four classes as
follows:
4.Essential gaseous environment :: OO22 and CO and CO22
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The possible reasons that obligate
anaerobe can not grow aerobically:
1. Deficiency of respiratory enzyme bearing high
redox potential
2. Deficiency of enzymes that degrade toxic oxygen
group, such as superoxide dismutase(SOD), catalase and
peroxidase.
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Proliferative way: Binary fission
Bacterial Growth Curve Bacterial Growth Curve
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The reproductive speed of most
bacteria is very fast, while some bacteria
such as Mycobacterium tuberculosis
grows very slow.
Reproductive speed:
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Generation time : The time takes for a
population of bacteria to double in number
• many common bacteria : 20 ~ 60 min
•most common pathogens in the body : 5 ~ 10
hours
•Mycobacterium tuberculosis in medium: 18~ 20
hours
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Bacterial population dynamics—the growth curveBacterial population dynamics—the growth curve
time
Log B
acterial Num
ber
Lag Logarithmic Stationary Decline
Live cell number
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Lag phase
• No growth
• Active metabolism
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Log phase
• Fast growth
• Typical biological properties
– Staining
– Shapes
– Chemical reactions
– Sensitivity to antimicrobial agents
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Stationary phase
• Constant number of live cells
• Atypical morphological properties
• Spores, exotoxins and antibiotics produced
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Decline phase
• Decreased number of live cells
• Collapse or atypical cells
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Based on the function and the chemical components: Basic Medium
contains the basic nutrients for the most bacterial growth; the base of other kind of media. e.g. broth.
Nutrient Medium/Enriched Medium Additional or special nutrients (e.g., serum, growth
factors, trace elements) are added to support some
fastidious bacterial growth.
e.g. blood agar.
Cultivation of Bacteria
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Selective Medium The medium that can prevent the certain bacterial growth while permitting others. e.g. SS agar
Differential Medium Some special substrates and indicators are added into the media in order to produce a visual differentiation When several bacteria grow on the same kind of medium. e.g. EMB agar (Eosinmethylene blue agar).
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Double sugar iron slant
Citrate slant
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Anaerobic Medium A medium for the cultivation of certain anaerobes. The medium contains reducing agent, such as nonsaturation fatty acid.
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Based on the physical state • Liquid medium:
– Without agar. – for the proliferation of bacteria.
• Solid medium: – 1.52.5% agar. – for the isolation and identification of bacteria – e.g., slant, Petri dishes/plates.
• Semisolid medium: – 0.30.5% agar. – for the observation of bacterial motility and preservation of bacteria.
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Bacterial growth patterns
• In liquid medium: Superficial growth; Turbidity/diffuse; Precipitate growing; (sediment)
• In solid medium:
Confluent growth / Smear :a cluster of microorganisms growing on a solid medium.
Colony: It is directly visible and arises from a single cell.
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• In semi-solid medium: – Only grow along the line of inoculation – Grow diffusely
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Bacterial classification
Please self-study
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Summary
2.The definitions of plasmid, capsule, flagellum,
pilus, spore, pyrogen, bactericin.
1.The difference between G + cell wall and G cell wall
3. Medical importance of four special structures
4.The characteristics of growth curve
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