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Bacterial Anatomy

Bacterial Anatomy. Rashmi.S. Anatomy of a Bacterial Cell. Description. Bacteria are Prokaryotic, unicellular that do not contain chlorophyll. Size of bacteria may range from 0.2-1.5 micrometer in diameter and 3-5 micrometer in length. DIFFERENCES BETWEEN PROKARYOTES AND EUKARYOTES.

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Bacterial Anatomy

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  1. Bacterial Anatomy Rashmi.S

  2. Anatomy of a Bacterial Cell

  3. Description • Bacteria are Prokaryotic, unicellular that do not contain chlorophyll. • Size of bacteria may range from 0.2-1.5 micrometer in diameter and 3-5 micrometer in length

  4. DIFFERENCES BETWEEN PROKARYOTES AND EUKARYOTES Character Prokaryotes Eukaryotes Nucleus: Nuclear Membrane Absent Present Nucleolus Absent Present Mitotic Division Absent Present Cytoplasm Cytoplasmic Streaming Absent Present Pinocytosis Absent Present Lysosomes Absent Present Golgi Apparatus Absent Present Endoplasmic Reticulum Absent Present Chemical Composition Sterols Absent Present Muramic Acid Present Absent Teichoic Acid Present Absent

  5. Classification of Bacteria based on their Shape • Cocci • Bacilli • Vibrio • Spirilla • Spirochetes • Actinomycetes • Mycoplasma

  6. Cellular Arrangement In Cocci, • Diplococci: Cocci arranged in pairs • Streptococci: Arranged in chains • Staphylococci: Arranged in grape like clusters

  7. In Bacilli, • Coccobacilli: Oval shaped • Palisades : Parallel, attached at any one end of the cell • Streptobacilli: In chains

  8. Vibrio Spirilla

  9. Mycoplasma Actinomycetes

  10. Structure of a Bacterial Cell(Bacterial Anatomy) • Examination of a bacterial cell reveals components of structures • Some external to cell wall • Others internal to cell wall

  11. Anatomy of a Bacterial Cell

  12. Demonstration of the cell wall • Plasmolysis • Microdissection • Specific Antibodies • Differential Staining • Electron Microscope

  13. Structure of the cell wall • Bacterial cell wall provides structural integrity to the cell. • The bacterial cell wall differs from that of all other organisms by the presence of Peptidoglycan • Peptidoglycan (Mucopeptide) is composed of alternating chains of .. • N -Acetyl Glucoseamine and N-Acetyl Muramic acid, which is cross linked by Peptide chains

  14. Structure of Peptidoglycan

  15. Peptidoglycan is responsible for the rigidity of the bacterial cell wall and for the determination of cell shape • Based on the composition of cell wall & Staining bacteria are classified into “Gram positive” and “Gram Negative’

  16. Gram’s Staining

  17. Gram Positive Cell wall • The Gram positive cell wall is characterized by the presence of a very thick Peptidoglycan layer • 20-80 nm thick • Cell wall contains90% Peptidoglycan and 10%Teichoic acid

  18. Interwoven in the cell wall of gram-positive are Teichoic acids and lipoteichoic acids. • Teichoic acids composed of polymers of glycerol, phosphates, and the sugar alcohol- ribitol.

  19. Teichoic acids constitute for the major surface antigens. Eg: In Streptococcus pneumoniaeTeichoic acid bears the antigenic determinants called the “Forssman antigen”

  20. Gram Negative Cell Wall • Gram negative cell wall contains a thin Peptidoglycan layer adjacent to the Cytoplasmic membrane, • In addition to the Peptidoglycan layer, the Gram negative cell wall also contains an additional outer membrane composed by Phospholipids and Lipopolysaccharide which face into the external environment.

  21. The LPS present on the Gm negative cell wall consists of 3 regions: • Polysaccharide determining O antigen • Core Polysaccharide • Glycolipid portion /Lipid A

  22. All the three factors are responsible for the endotoxic activities……… • LPS Endotoxin causes a form of Septic Shock for which there is no direct treatment

  23. Cytoplasmic Membrane • It is a thin layer lining the inner surface of the cell wall. • Semipermiable membrane controlling the flow of metabolites • Chemically ,consists of Lipoprotein and carbohydrates. Sterols are absent

  24. Cytoplasm • Colloidal system of variety of organic and inorganic solutes in Viscous watery solution • No ER,& Mitochondria • Contains Mesosomes Inclusions and Vacuoles

  25. Mesosomes • Vesicular, convoluted invaginations of the plasma membrane • Prominent in GM+ bacteria • Principal sites of Respiratory enzymes • Analogous to mitochondria in Eukaryotes

  26. Nucleus • Bacterial nuclei “have no nuclear membrane “or the nucleolus. • Genome consists of a single double stranded DNA. • Might be a Circular form or may be open under certain condition to form a long chain.

  27. Plasmids • Extra chromosomal DNA • Circular capable of autonomous replication. • Transferred from one bacterium to another .

  28. Importance • Their presence confers certain special characters…… • Toxigenicity • Antibiotic Resistance • Ability to use certain unusual components as nutrients

  29. Structures external to Bacteria • Capsule • Flagella • Pili(Fimbriae)

  30. Capsule • Viscid material secreted by bacteria around the cell surface • Capsule is a sharply defined, organized structure (Eg: Pneumococcus) • Loose undemarkated structure as in Lueconostoc is a Slime layer.

  31. Colorless capsule surrounding the bacterial cell

  32. Capsular Staining

  33. Most bacterial capsules are composed of Polysaccharides Eg: Klebsiella pneumoniae • A few capsules are Polypeptides Eg: Bacillus anthracis

  34. Quellung Reaction • Described by Neufeld(1902). • Serological method of demonstrating the capsule. • Suspension of capsulated bacterium is mixed with its specific anticapsular serum & examined under the microscope ,capsule appears prominent & swollen. • Used to type Pneumococci.

  35. Functions of Capsules • Antiphagocytic,thus contribute “Virulence”. • Protects against “Lysozyme” • Promote attachment of bacteria to surface(Eg: Streptococcusmutans). • Permits bacteria to adhere to Medical Implants & Catheters.

  36. Toxicity to host cell – Eg: Bacteroidesfragilis. • Provide protection against temporary drying. • Block the attachment ofBacteriophages.

  37. Applications: • Used in serological typing • Detection of capsule in Blood, CSF provides a rapid method of diagnosis • Used in preparation of vaccines Eg: H.influenzae

  38. Flagella • Unbranched, long ,filaments ,made up of protein “Flagellin” • Organs of locomotion • Found in all motile bacteria except Spirochetes

  39. Flagella are highly antigenic, • Termed as the ‘H’ Antigen. • Some of the immune responses are directed against these proteins.

  40. Structure • 3-20 Micrometer. • Each flagellum consists of 3 parts 1.Filament 2.Hook 3.Basal body

  41. Flagellar Arrangement

  42. Kinds of Motility: • Darting motility : V.cholerae • Tumbling motility: L.monocyctogenes • Cork &screw motility: T.pallidum • Stately motile : Clostridium spp. • Serpentine motility: Salmonella (Except S.gallonarum pullorum)

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