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Bacterial AnatomyBacterial Anatomy
Rashmi.SRashmi.S
Anatomy of a Bacterial Cell
DescriptionDescription
Bacteria are Prokaryotic, Bacteria are Prokaryotic, unicellular that do not contain unicellular that do not contain chlorophyll.chlorophyll.
Size of bacteria may range from Size of bacteria may range from 0.2-1.5 micrometer in diameter 0.2-1.5 micrometer in diameter and 3-5 micrometer in lengthand 3-5 micrometer in length
DIFFERENCES BETWEEN PROKARYOTES AND DIFFERENCES BETWEEN PROKARYOTES AND EUKARYOTESEUKARYOTES
CharacterCharacter Prokaryotes Prokaryotes Eukaryotes Eukaryotes
Nucleus:Nucleus:Nuclear MembraneNuclear Membrane Absent Absent Present Present
Nucleolus AbsentNucleolus Absent Present Present Mitotic Division AbsentMitotic Division Absent PresentPresent
CytoplasmCytoplasmCytoplasmic Streaming AbsentCytoplasmic Streaming Absent PresentPresentPinocytosis Absent Pinocytosis Absent Present Present Lysosomes Absent Lysosomes Absent Present Present Golgi Apparatus AbsentGolgi Apparatus Absent PresentPresentEndoplasmic Reticulum AbsentEndoplasmic Reticulum Absent PresentPresentChemical CompositionChemical CompositionSterols AbsentSterols Absent PresentPresentMuramic Acid PresentMuramic Acid Present AbsentAbsentTeichoic Acid PresentTeichoic Acid Present AbsentAbsent
Classification of Bacteria based Classification of Bacteria based on their Shapeon their Shape
CocciCocci BacilliBacilli VibrioVibrio SpirillaSpirilla SpirochetesSpirochetes ActinomycetesActinomycetes MycoplasmaMycoplasma
Cellular Arrangement Cellular Arrangement
In Cocci,In Cocci, Diplococci: Cocci arranged in pairsDiplococci: Cocci arranged in pairs
Streptococci: Arranged in chainsStreptococci: Arranged in chains
Staphylococci: Arranged in grape like Staphylococci: Arranged in grape like clustersclusters
In Bacilli,In Bacilli, Coccobacilli: Oval shapedCoccobacilli: Oval shaped
Palisades : Parallel, attached at any Palisades : Parallel, attached at any one end of the cellone end of the cell
Streptobacilli: In chainsStreptobacilli: In chains
VibrioVibrio Spirilla
Actinomycetes Mycoplasma
Structure of a Bacterial CellStructure of a Bacterial Cell(Bacterial Anatomy)(Bacterial Anatomy)
Examination of a bacterial cell reveals Examination of a bacterial cell reveals components of structurescomponents of structures
Some external to cell wall Some external to cell wall
Others internal to cell wallOthers internal to cell wall
Anatomy of a Bacterial Cell
Demonstration of the cell Demonstration of the cell wallwall
PlasmolysisPlasmolysis MicrodissectionMicrodissection Specific AntibodiesSpecific Antibodies Differential StainingDifferential Staining Electron MicroscopeElectron Microscope
Structure of the cell wallStructure of the cell wall
Bacterial Bacterial cell wallcell wall provides structural provides structural integrity to the cell. integrity to the cell.
The bacterial cell wall differs from that of all The bacterial cell wall differs from that of all other organisms by the presence of other organisms by the presence of PeptidoglycanPeptidoglycan
Peptidoglycan (Mucopeptide) is composed of Peptidoglycan (Mucopeptide) is composed of alternating chains of ..alternating chains of ..
N -Acetyl Glucoseamine and N-Acetyl N -Acetyl Glucoseamine and N-Acetyl Muramic acid,Muramic acid, which is cross linked by which is cross linked by Peptide chainsPeptide chains
Structure of Peptidoglycan
PeptidoglycanPeptidoglycan is responsible for is responsible for the rigidity of the bacterial cell the rigidity of the bacterial cell wall and for the determination of wall and for the determination of cell shapecell shape
Based on the Based on the composition of cell composition of cell wall & Stainingwall & Staining bacteria are bacteria are classified into “classified into “Gram positive”Gram positive” and and ““Gram Negative’Gram Negative’
Gram’s Staining
Gram Positive Cell wallGram Positive Cell wall
The The Gram positiveGram positive cell wall is cell wall is characterized by the presence of a characterized by the presence of a very thick very thick PeptidoglycanPeptidoglycan layer layer
20-80 nm thick20-80 nm thick Cell wall contains90% Peptidoglycan Cell wall contains90% Peptidoglycan
and 10%Teichoic acidand 10%Teichoic acid
Interwoven in the cell wall of gram-Interwoven in the cell wall of gram-positive are positive are Teichoic acidsTeichoic acids and and lipoteichoic acidslipoteichoic acids. .
Teichoic acids composed of polymers Teichoic acids composed of polymers of glycerol, phosphates, and the sugar of glycerol, phosphates, and the sugar alcohol- ribitol. alcohol- ribitol.
Teichoic acids constitute for the major Teichoic acids constitute for the major surface antigens.surface antigens.
Eg: In Eg: In Streptococcus pneumoniaeStreptococcus pneumoniae Teichoic acid bears the antigenic Teichoic acid bears the antigenic determinants called the “Forssman determinants called the “Forssman antigen”antigen”
Gram Negative Cell WallGram Negative Cell Wall
Gram negative cell wall contains a thin Gram negative cell wall contains a thin PeptidoglycanPeptidoglycan layer adjacent to the layer adjacent to the Cytoplasmic membraneCytoplasmic membrane, ,
In addition to the In addition to the PeptidoglycanPeptidoglycan layer, layer, the Gram negative cell wall also the Gram negative cell wall also contains an additional outer membrane contains an additional outer membrane composed by composed by PhospholipidsPhospholipids and and Lipopolysaccharide which face into the Lipopolysaccharide which face into the external environment. external environment.
The LPS present on the Gm negative The LPS present on the Gm negative cell wall consists of 3 regions:cell wall consists of 3 regions:
Polysaccharide determining O antigenPolysaccharide determining O antigen Core PolysaccharideCore Polysaccharide Glycolipid portion /Lipid AGlycolipid portion /Lipid A
All the three factors are responsible All the three factors are responsible for the endotoxic activities………for the endotoxic activities………
LPS Endotoxin causes a form of Septic LPS Endotoxin causes a form of Septic Shock for which there is no direct Shock for which there is no direct treatmenttreatment
Cytoplasmic MembraneCytoplasmic Membrane
It is a thin layer lining the inner It is a thin layer lining the inner surface of the cell wall.surface of the cell wall.
Semipermiable membrane controlling Semipermiable membrane controlling the flow of metabolitesthe flow of metabolites
Chemically ,consists of Lipoprotein Chemically ,consists of Lipoprotein and carbohydrates. Sterols are absentand carbohydrates. Sterols are absent
CytoplasmCytoplasm
Colloidal system of variety of organic Colloidal system of variety of organic and inorganic solutes in Viscous and inorganic solutes in Viscous watery solutionwatery solution
No ER,& MitochondriaNo ER,& Mitochondria
Contains Mesosomes Inclusions and Contains Mesosomes Inclusions and VacuolesVacuoles
MesosomesMesosomes
Vesicular, convoluted invaginations of Vesicular, convoluted invaginations of the plasma membranethe plasma membrane
Prominent in GM+ bacteriaProminent in GM+ bacteria Principal sites of Respiratory enzymesPrincipal sites of Respiratory enzymes Analogous to mitochondria in Analogous to mitochondria in
EukaryotesEukaryotes
NucleusNucleus
Bacterial nuclei “Bacterial nuclei “have no nuclear have no nuclear membranemembrane “ “or the nucleolus.or the nucleolus.
Genome consists of a single double Genome consists of a single double stranded DNA.stranded DNA.
Might be a Circular form or may be Might be a Circular form or may be open under certain condition to form open under certain condition to form a long chain.a long chain.
PlasmidsPlasmids
Extra chromosomal DNAExtra chromosomal DNA
Circular capable of autonomous Circular capable of autonomous replication.replication.
Transferred from one bacterium to Transferred from one bacterium to another .another .
ImportanceImportance
Their presence confers Their presence confers certain special characters……certain special characters……
ToxigenicityToxigenicityAntibiotic ResistanceAntibiotic ResistanceAbility to use certain unusual Ability to use certain unusual
components as nutrientscomponents as nutrients
Structures external to Structures external to BacteriaBacteria
CapsuleCapsule
FlagellaFlagella
Pili(Fimbriae)Pili(Fimbriae)
CapsuleCapsule
Viscid material secreted by bacteria Viscid material secreted by bacteria around the cell surfacearound the cell surface
CapsuleCapsule is a sharply defined, organized is a sharply defined, organized structure (structure (Eg: Eg: PneumococcusPneumococcus))
Loose undemarkated structure as in Loose undemarkated structure as in Lueconostoc Lueconostoc is a is a Slime layer.Slime layer.
Colorless capsule surrounding the bacterial cell
Capsular Staining
Most bacterial capsules are composed Most bacterial capsules are composed of Polysaccharidesof Polysaccharides
Eg: Eg: Klebsiella pneumoniaeKlebsiella pneumoniae
A few capsules are PolypeptidesA few capsules are Polypeptides
Eg: Eg: Bacillus anthracisBacillus anthracis
Quellung ReactionQuellung Reaction
Described by Described by Neufeld(1902).Neufeld(1902). Serological method of demonstrating the Serological method of demonstrating the
capsule.capsule. Suspension of capsulated bacterium is Suspension of capsulated bacterium is
mixed with its specific anticapsular mixed with its specific anticapsular serum & examined under the serum & examined under the microscope ,capsule appears prominent microscope ,capsule appears prominent & swollen.& swollen.
Used to type Used to type Pneumococci.Pneumococci.
Functions of CapsulesFunctions of Capsules
Antiphagocytic,thus contribute Antiphagocytic,thus contribute “Virulence”.“Virulence”.
Protects against “Lysozyme”Protects against “Lysozyme” Promote attachment of bacteria to Promote attachment of bacteria to
surface(Eg: surface(Eg: StreptococcusStreptococcus mutansmutans).). Permits bacteria to adhere to Permits bacteria to adhere to
Medical Implants & Catheters.Medical Implants & Catheters.
Toxicity to host cell – Eg: Toxicity to host cell – Eg: BacteroidesBacteroides fragilis.fragilis.
Provide protection against Provide protection against temporary drying.temporary drying.
Block the attachment Block the attachment ofBacteriophagesofBacteriophages..
Applications:Applications:
Used in serological typingUsed in serological typing
Detection of capsule in Blood, CSF Detection of capsule in Blood, CSF provides a rapid method of diagnosisprovides a rapid method of diagnosis
Used in preparation of vaccinesUsed in preparation of vaccinesEg: H.influenzaeEg: H.influenzae
FlagellaFlagella
Unbranched, long ,filaments ,made up Unbranched, long ,filaments ,made up of protein “of protein “FlagellinFlagellin””
Organs of locomotionOrgans of locomotion
Found in all motile bacteria except Found in all motile bacteria except SpirochetesSpirochetes
Flagella are highly antigenic,Flagella are highly antigenic,
Termed as the Termed as the ‘H’ Antigen‘H’ Antigen..
Some of the immune responses are Some of the immune responses are directed against these proteins.directed against these proteins.
StructureStructure
3-20 Micrometer.3-20 Micrometer.
Each flagellum consists of 3 partsEach flagellum consists of 3 parts
1.Filament 1.Filament
2.Hook2.Hook
3.Basal body3.Basal body
Flagellar Arrangement
Kinds of MotilityKinds of Motility:: Darting motilityDarting motility : : V.choleraeV.cholerae Tumbling motilityTumbling motility::
L.monocyctogenesL.monocyctogenes Cork &screw motilityCork &screw motility:: T.pallidumT.pallidum Stately motile Stately motile : : Clostridium Clostridium
spp.spp. Serpentine motilitySerpentine motility: : Salmonella Salmonella
(Except S.gallonarum pullorum)(Except S.gallonarum pullorum)
Detection of motility :Detection of motility :
Direct observation by hanging Direct observation by hanging dropdrop
Dark field microscopyDark field microscopyMotility mediaMotility media
Flagellar stainingFlagellar staining
Electron microscopyElectron microscopy
Immunological detection Immunological detection of “H” antigenof “H” antigen
FimbriaeFimbriae
Hair like surface appendagesHair like surface appendages
0.5-10 nm thick0.5-10 nm thick
Shorter thinner than flagellaShorter thinner than flagella
Formed of protein subunits – PilinFormed of protein subunits – Pilin
FunctionsFunctions
Organs of adhesionOrgans of adhesion Forms “Pellicles”Forms “Pellicles” Hemagglutination –Clumping of RBC’s Hemagglutination –Clumping of RBC’s
((EscherichiaEscherichia,,KlebsiellaKlebsiella)) Special type of Fimbriae called Sex Special type of Fimbriae called Sex
pili,help in attachment to other pili,help in attachment to other bacteriabacteria
EndosporesEndospores Highly resistant stages of bacteriaHighly resistant stages of bacteria
Spores germinate to form a single Spores germinate to form a single Vegitative cell.Vegitative cell.
It is formed inside the cell .It is formed inside the cell .
Eg: Eg: BacillusBacillus, , ClostridiumClostridium
Endospore
Core contains the Nuclear bodyCore contains the Nuclear bodySurrounded by a Spore Wall.Surrounded by a Spore Wall.Outside this is a thick Spore Outside this is a thick Spore
cortexcortexThis is covered in turn by a This is covered in turn by a
tough Spore coat.tough Spore coat.Exosporium is additional outer Exosporium is additional outer
covering, which exhibits ridges covering, which exhibits ridges and groovesand grooves
Factor responsible for the resistance Factor responsible for the resistance of sporesof spores
Presence of calcium dipicolinic acidPresence of calcium dipicolinic acid
Endospore inside bacteria
Position of SporesA = oval, terminal;
B = rectangular, terminal;
C = rectangular, sub terminal,
D = rectangular, central;
E = circular, terminal;
F = circular, central;
G = terminal, club-shaped.
Pleomorphism and Involution Pleomorphism and Involution formsforms
Process of exhibiting variation in the shape Process of exhibiting variation in the shape and size of individual cells – Pleomorphismand size of individual cells – Pleomorphism
Eg: H.influenzaeEg: H.influenzae Certain bacteria exhibit swollen and Certain bacteria exhibit swollen and
aberrant forms in ageing cultures – aberrant forms in ageing cultures – Involution formsInvolution forms
This may be due to defective cell wall This may be due to defective cell wall synthesis or due to Autolytic Enzymessynthesis or due to Autolytic Enzymes
Eg: Eg: Yersinia, GonococcusYersinia, Gonococcus
Protoplasts,Spheroplasts and Protoplasts,Spheroplasts and L-FormsL-Forms
Removal of bacterial cell wall by Removal of bacterial cell wall by hydrolysis with Lysozyme or hydrolysis with Lysozyme or antibiotics like Penicillin, liberates ..antibiotics like Penicillin, liberates ..
““Protoplasts” from Gram positive cellsProtoplasts” from Gram positive cells ““Spheroplasts” from Gram negative Spheroplasts” from Gram negative
cellcell
(retain the outer membrane and PG.)(retain the outer membrane and PG.)
When Protoplasts and Spheroplasts When Protoplasts and Spheroplasts are able to grow and divide they are are able to grow and divide they are called the called the L-Forms.L-Forms.
First observed by Kleineberger-NobelFirst observed by Kleineberger-Nobel Named it as L forms after Lister Named it as L forms after Lister
Institute London.Institute London.
Eg: Streptobacillus moniliformisEg: Streptobacillus moniliformis
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