Four levels of protein structure Linear Sub-Structure 3D Structure Complex Structure.
Bacterial Cell Structure Structure Dr. Majid Zare Bidaki (PhD in Microbiology, Assistant professor)...
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Transcript of Bacterial Cell Structure Structure Dr. Majid Zare Bidaki (PhD in Microbiology, Assistant professor)...
Bacterial CellBacterial Cell StructureStructure
Dr. Majid Zare Bidaki(PhD in Microbiology, Assistant professor)
Birjand University of Medical Science
ReferencesReferences
1. Jawetz, Melnick, & Adelberg; Medical Microbiology, 24th ed.
2. Zinsser, Hans, And Joklik, Wolfgang K.; Medical Microbiology, 17th ed.
3. Baron, Samuel; Medical Microbiology, 4th ed.
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Antonie van LeeuwenhoekAntonie van Leeuwenhoek
First to observe living microbes
his single-lens magnified up to 300X
(1632-1723)
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5
Louis Pasteur (1822-1895) Louis Pasteur (1822-1895)
Showed microbes caused fermentation & spoilage
Disproved spontaneous generation of microbes
Developed aseptic techniques.
Developed a rabies vaccine.
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Robert Koch Robert Koch
Proposed: Germ theory of disease
Developed: pure culture methods.
Identified: cause of anthrax, TB, & Cholera.
(1843-1910)
Acellular and cellular Microorganisms
Acellular: VirusesViruses ViroidsViroids PrionsPrions
Cellular:BacteriaBacteriafungifungiProtista: Protozoa & algaeProtista: Protozoa & algaehelminths (worms) helminths (worms)
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Prokaryotic or EukaryoticProkaryotic or Eukaryotic
Prokaryotes vs EukaryotesProkaryotes vs Eukaryotes
Size smaller Larger
Nucleus - +
Organelles - +
Chromosomes 1 circular Multiple, linear
Ribosomes smaller 70s Larger 80sr
In prokaryotes against Eukaryotes, cell membranes lack In prokaryotes against Eukaryotes, cell membranes lack sterols (e.g. cholesterol)sterols (e.g. cholesterol)
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Scientific nomenclatureScientific nomenclature
Binomial (scientific) nomenclature Gives each microbe 2 namesGenusGenus - noun, always capitalizedspeciesspecies - adjective, lowercase
Both italicized or underlined– Staphylococcus aureus (S. aureus)– Escherichia coli (E. coli)
Bacterial shapesBacterial shapes
Cytoplasmic membrane Cytoplasmic membrane ProtoplastProtoplast
SpheroplastSpheroplast L formsL forms
Gram positiveGram positive Gram negativeGram negative
LipopolysaccharideLipopolysaccharide
Lipid A• Glucosamine disaccharide• Beta hydroxy fatty acids
Core • Heptoses• Ketodeoxyoctonic acid
O-antigenHighly variable
(Hydroxy myritic Acid)
LPS functionLPS functionEndotoxinsEndotoxinsExotoxinsExotoxins
PeptidoglycanPeptidoglycan
Gram positiveGram positive
Gram negativeGram negative
4 groups based on cell wall 4 groups based on cell wall compositioncomposition
1. Gram positive cells
2. Gram negative cells
3. Bacteria without cell walls
4. Bacteria with chemically unique cell walls
Gram positive wall
Gram negative cell wallGram negative cell wall
CytoplasmCytoplasm
CytoplasmCytoplasm
Lipoteichoic acidPeptidoglycan-teichoic acid
Cytoplasmic membrane
Inner (cytoplasmic) membrane
Outer Membrane
LipopolysaccharidePorin
lipoprotein
Peri
plas
mic
spa
ce
r r rrr
r
Gram Positive Cell EnvelopeGram Positive Cell Envelope
rrrr
Lipoteichoic acidPeptidoglycan-teichoic acid
Cytoplasmic membrane
Bacteria classification based on Bacteria classification based on cell wall structurecell wall structure
Grasilicutes (Gram Negative)Grasilicutes (Gram Negative)Firmicutes (Gram Positive)Firmicutes (Gram Positive)Tenricutes (with no Cell wall)Tenricutes (with no Cell wall)Mendosicutes (with no Peptidoglycan in Mendosicutes (with no Peptidoglycan in
cell wall)cell wall)
Major Taxonomic Groups of BacteriaMajor Taxonomic Groups of Bacteria
Gracilicutes – gram-negative cell walls, thin-skinned
Firmicutes – gram-positive cell walls, thick skinned
Tenericutes – lack a cell wall & are softMendosicutes – archaea, primitive procaryotes
with unusual cell walls & nutritional habits
CapsuleCapsule
2 types1. Macro capsule - highly organized, tightly
attached2. Micro capsule, Slime layer or Glycocalyx -
loosely organized and attached
Functions attachment inhibits killing by white blood cells Receptor (K antigen)
2 Types of Capsule2 Types of Capsule
BiofilmsBiofilms
FlagellaFlagella
Fimbrea (Pili)Fimbrea (Pili)
Adhesion to other cells and surfaces
StructureStructure
Pili & Sex pili
Rigid tubular structure made of pielin protein
Found mostly in Gram negative cells
FunctionsFunctions Adhesionjoins bacterial cells for DNA transfer (Conjugation)
ConjugationConjugation
CytoplasmCytoplasmdense gelatinous solution of sugars, amino
acids, & salts70-80% waterserves as solvent for materials used in all
cell functions
ChromosomeChromosome
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
plasmidsplasmids
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
RibosomesRibosomes
made of 60% ribosomal RNA & 40% protein
consist of 2 subunits: large (50 S) & small (30 S)
procaryotic differ from eucaryotic ribosomes in
size & number of proteins
site of protein synthesis
All bacterial cells have ribosomes.
Inclusions, granulesInclusions, granules
intracellular storage bodies
vary in size, number & content
bacterial cell can use them when
environmental sources are depleted
Examples: glycogen, sulfur and polyphosphate granules,
poly-b-hydroxybutyrate, gas vesicles for floating.
endosporesendospores
Important components in endospore: Important components in endospore:
CalciumCalciumDipicolinic AcidDipicolinic Acid
The Endospore structureThe Endospore structure
Spore structureSpore structure
Spherical or Oval
Terminal, subterminal or central
Bulging or nobulging
Growth in BacteriaGrowth in Bacteria
Temperature
Nutrients
pH
Osmotic pressure
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
Temperature Temperature
3 temperature adaptation groups
Bacterial MetabolismBacterial Metabolism
PhototrophPhotoautotroph (Photolitotroph) Photoheterotroph (Photoorganotroph)
ChemotrophChemoautotroph (ChemolitotrophChemoheterotroph (Chemoorganotroph)
Stages of metabolism in Stages of metabolism in chemoheterotrophic bacteriachemoheterotrophic bacteria
Digestion
Absorption (Passive and active transportation)
Preparation for oxidation
Oxidation
Oxidation & ReductionOxidation & Reduction
X Ye- & H+ Cytochromes, …. Cytochromes, ….
Oxygen requirementsOxygen requirements
Bacterial growth Bacterial growth
Binary divisionBinary division
Microbial growth calculationMicrobial growth calculation
b = a X 2n
G (Generation time) = T / n
(n = The number of generations, T = The total time of growth for the population)
The curve of bacterial growth in a closed The curve of bacterial growth in a closed cultureculture
Growth Curve
Bacterial growth in a Bacterial growth in a continues culturecontinues culture
Con
tinuo
us C
ultu
re, C
hem
osta
t
Chemostats are a means of keeping a culture in log phase indefinitely.
Measuring the bacterial growthMeasuring the bacterial growth
• Measuring the mass of bacteria
• Measuring the number of bacteria
FermentationFermentation
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
FermentationFermentation
Methods in bacterial identificationMethods in bacterial identification
1. Microscopic morphology
2. Macroscopic morphology – colony appearance
3. Physiological / biochemical characteristics
4. Chemical analysis
5. Serological analysis
6. Genetic & molecular analysis G + C base composition DNA analysis using genetic probes Nucleic acid sequencing & rRNA analysis
Bacterial ColoniesBacterial Colonies
• Standard Bacterial Count
• Colony-Forming Units
• Plaque-Forming Units
•Spread Plate
• Pour Plate
• Soft-Agar Overlay
MediumMedium
DefinitionDefinitionTypes based on solidity:Types based on solidity:
1. Liquid medium (Name broth)
BHI, TSB, SF, NB, …
2. Solid medium (Name agar)
Blood agar, Nutrient agar, chocolate agar, Columbia agar, EMB
3. Semi-solid medium
SIM
Culture mediaCulture media
General medium
Special medium
Differential medium
Enrichment medium (….. & cold enrichment)
Transport medium (Stwart, Carry Blair, …)
Galleries
Types of culture methodsTypes of culture methods
Isolation culture
Spread culture
Pour plate culture
Colony count culture