1. Bacterial Structure
Almugadam B Saad
Lecturer of medical microbiology Full name
Babiker Saad Almugadam Yousif
Faculty of medical laboratory sciences
University of El Imam El Mahadi
Kosti-Sudan
MSc University of Khartoum
BSc University of El Imam El Mahadi
Babiker Saad Almugadam Yousif
2. Bacterial Structure
learning objectives:
- Components of bacteriaStructure - Components of bacteria
- Function of each component
- Demonstration of different
structure
Structure
4. Components of bacterial cell
- Classify to :
A- Essential components :
Cell wall , Cell membrane
Include : Ribosome's , Nucloid
Meosome , Periplasm
B- Non Essential components :
Capsule , pili
Include : Flagella , Endopore
Plasmid , Granule
Glycocalyx
- Appendix (External structure ) : Term relate to Flagella ,
Capsule , pili .
5. Cell wall
-Polymer of peptidoglycan(also called murein , mucopeptide ,
glycopeptide glycosaminpeptides) and other components
which include:
polyscharides + teichoic acid in Gram+ve
protein plus
lipid+lipoprotein+lipopolysacharides in Gram-ve
-Murein : reponsible of shape and strength of cell .This layer-Murein : reponsible of shape and strength of cell .This layer
thick in Gram+ and thiner in Gram-ve.
-Teichoic acid : either glycerol or ribitol teichoic acid.reponsible
of binding with cations as magnesium.
-Lipopolysacharides: consist of lipid A and polyscharides
reponsible of somaticO Ag and endotoxin.
-Cell wall deficient bacteria include Mycoplasma and L form
bacteria .
6. L-Form bacteria:
- Definition : Bacteria their murein has been eliminated or
modified and get spheroplast in case of
Gram-ve and protoplast in case of Gram+ve
which divide and give L-form bacteria.
- Origin of L-form : Form as result of
1- Spontaneous : as Bacteroides
2- Growth in presence of cell inhibitor
3- Destruction of cell wall by Ab and complement
4- Deprivation of natureal requirement for cell wall4- Deprivation of natureal requirement for cell wall
synthesis
- classification of L-form according to reversion :
1-Stable : reverse to grow as bacteria when the cause is
removed
2- Unstable : grow as L-form bacteria when the cause is
removed
- Colonies of L-form :
A- On solid media : Has fried egg appearance
B- On liquid media : Grow in form of clump
7. - Maintaince of L-form: Require special media ,as soft agar
media
- causes of bacteria cell lysis :
1- Bacteriacidal drugs 2- Bacteriophages
3- Serum component 4- Autolysis
5- Osmatic , when its hypotonic 6- Enzyme digestion
7- Physical agent 8- Chemical agent
9- Deprivation of nutrient necessary for cell wall synthesis
8. Periplasmic membrane
- Space between cytoplasmic membrane and outer
membrane in Gram-ve , contain hydrolytic enzymes and
B-lactmase .
Cytoplasmic membrane
-Also known as cell membrane . Its lipoprotein , compose of
lipid(30%) and protein (70%) , not contain lecithin or sterol
(expect mycoplasma has sterol).(expect mycoplasma has sterol).
-Function :
1- Selective permability 2- Act as osmatic barier
3-Passive and active transport
4- Contain cytochrome enzyme , tricarboxylic cycle , and set
of polymerized enzymes require for cell wall and
extracellular structure
5- Site of biosynthesis of cell wall , DNA , and membrane
lipid
9. Mesosome
- Is folded to word cytoplasm
Cytoplasm
- Compose of 80% water. also contain protein , nucleic acid ,
lipid , small amount of salts. No organelles (mitochondria or
Golgi apparatus)
NucleusNucleus
- Also named nucleiod. Lack nuclear membrane and nuclei.
Contain single circular chromosome.
Plasmid
- Extrachromosomal circular DNA , replicate independent of
bacterial chromosome , virulence factor , carry gene for
antibiotics resistant . Transmissible
Can be Non transmissible
10. Flagella
- Fibril structure , bacteria can machinery or chemically
deflagellate but it can again generate it.
A- External part : that form of
- Consist of two part : soluble protein called flagellin
B- Basal (internal) : which anchoring
inside the membrane
- Function of flagella :- Function of flagella :
1-Movement 2-Virulence factor 3-Atigenic
A- True movement
Type of movement : B- Convection current movement
C- Brownian movement
- Arrangement of flagella : according to mode of insertion
1- Monotrichous
A- Polar flagella : 2- Amphitrichous
3- Lofotrichous (Polar multitrichous)
B- Peritrichous (Lateral) : arise aslight distance away from pole
11. - Demonstration of flagella :
1-Microscopy : by EM , or dark field , or Light microscopy
using special stain (leifson stain and Ryus
stain)
2-Serology : by antisera
12. Fimbriae and Pili
- Haire like projections , Compose of protein called pilin ,
receptor for some viruses , produce when bacteria grow in fluid
media(Fibril phase). Adhere to different type of tissue as RBCs
leading to hemoagglutination phenomina that use to detect it .
- Classification:
A- according to function :
1- Common pili (Adhesion) 2- Sex pili (F pili)
B- according to adherence properties :B- according to adherence properties :
1- Type 1 2- Type 2
3- Type 3 4- Type 4
- Function :
1- Attachment and Adhesion 2- Virulence factor
3- Transfer of gene from one bacteria to another during
conjugation (Sex pili) .
- Demonstration :
1-Microscopy : by EM 2- Serology : hemoagglutination test
13. Capsule
- Found in natural specimen , It gelatinous layer cover cell wall
- Compose mainly of water and the remainder is polymer of
polysacharide except B.anthracis (polymer of polypeptides)
and S.pyogen (hylouronic acid).
Homopolymer
- Polyscharides polymer two types:
Heteroplymer
- Classify to :- Classify to :
1- Macro capsule (20um or more) 2- Micro capsule
- Function :
1- Virulence factor 2- Antigenic (K Ag) 3- Antiphagocytic
- Demonstration :
1- Microscopy : by EM or phase contrast , or by Light
microscope using capsule stain (best India ink stain)
2- Serology : by quelling reaction or latex agglutination
test using specific antisera
14. Slime layer
-It colloid material secreted by capsulated and noncapsulated
bacteria. In capsulated bacteria , Its identical and typical
antigencity to capsule.Also called loose slime or free slime.
-When form in fluid media it disappear , because it soluble in
water . While in sold media , it form a round colonies which
become mucoid.
15. Spore (endospore):
-Its resistant structure , Formed by process of sporulation
when the condition unfavurable for vegetative growth. Spore
forming bacteria produce endospore.
-Spore shape:
1.Oval
2.Round
3.Elongated3.Elongated
-Spore position :
1.Central
2.Subterminal(Lateral)
3.Terminal
-Spore consist of ?
-Character which acquired by spore ?
-An example of spore forming bacteria : Bacillus species and
Clostridia species
16. -Endospore demonstration :
endospore not seen indirect specimen(seen in culture).appear
as unstained area in gram stain , dark blue with toluidine stain ,
and as refractile body under phase contrast microscope in wet
unstained film . Can be detect by light microscope
by using of Malachite green method or modified ziehl nelsonby using of Malachite green method or modified ziehl nelson
method.
17. Inclusion Granule
- Found in cytoplasm , present when bacteria grow in rich environment and
absent in case of starvation .
- Types according to their constituents :
1.Volutin granules 2.Lipid granules
3.Sulphur granules 4.Polysaccharides granules
18. 1.Volutin granules :
-Made up of polymetaphosphate , RNA , and protein.Produce
C.diphteriae and G.vaginalis.
-Also called metachromatic granules , and babes ernst granules
-Demonstration:
Appear as opaque in electron microscope. Stain metachromaticallyAppear as opaque in electron microscope. Stain metachromatically
red purple with methylene blue or toulidine blue .
Can be clearly demonstrate by special stain (Albert stain or Niesser
stain )
Albert stain
Bacteria stain green
Granules stain blue-black
