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  • the bacterial  cell wall  provides structural integrity to the cell. In  prokaryotes , the primary function of the cell wall is to protect the cell from internal  turgor pressure  caused by the much higher concentrations of proteins and other molecules inside the cell compared to its external environment. The bacterial cell wall differs from that of all other organisms by the presence of  peptidoglycan  (poly- N -acetyl glucosamine and  N -acetylmuramic acid), which is located immediately outside of the  cytoplasmic membrane .  Peptidoglycan  is responsible for the rigidity of the bacterial cell wall and for the determination of cell shape. It is relatively porous and is not considered to be a permeability barrier for small substrates. While all bacterial cell walls (with a few exceptions e.g. intracellular parasites such as  Mycoplasma ) contain peptidoglycan, not all cell walls have the same overall structures. Since the cell wall is required for bacterial survival, but is absent in  eukaryotes , several antibiotics ( penicillins  and  cephalosporins ) stop bacterial infections by interfering with cell wall synthesis, while having no effects on human cells.

Transcript

  • 1. MORPHOLOGY OF BACTERIA The Bacterial Cell
  • 2. Key Words Prokaryote Outer membrane Eubacteria (Bacteria) Periplasmic space Oxidative phosphorylation Eukaryote Spheroplast/protoplast Plasmid Flagella Chromosome Chemotaxis Ribosome Axial filament Peptidoglycan (murein, mucopeptide) Gram stain Gram negative Storage Granules Gram positive Pili (fimbriae) Cell envelope Capsule (slime layer, glycocalyx) Cell membrane Endospore (spore) Cell wall Archaebacteria ( Archaea )
  • 3. PROKARYOTES EUBACTERIA ARCHAEA EUKARYOTES
  • 4. Prokaryotes (Bacteria)
    • Eubacter "True" bacteria
      • human pathogens
      • clinical or environmental
      • one kingdom
    • Archaea
      • Environmental organisms
      • second kingdom
  • 5. Introduction
    • Bacteria despite their simplicity, contain a well developed cell structure which is responsible for many of their unique biological properties. Many structural features are unique to bacteria and are not found among eukaryotes.
  • 6. Cell Morphology
    •   The most elemental structural property of bacteria is cell morphology (shape).
    • Bacteria are classified by shape into three basic groups:
        • cocci (spherical)
        • bacilli (rod-like)
        • spirochetes (spiral)
    • Some bacteria are variable in shape and said to pleomorphic.
    • The shape of a bacteria is determined by its rigid cell wall.
    • The microscopic appearance of a bacterium is one of the most important criteria used in identification.
  • 7. Bacteria come in a wide variety of shapes
  • 8.
    • The arrangement of bacteria is important.
    • Example:
        • Cocci in pairs (diplococci)
        • Cocci in chains (streptococci)
        • Cocci in clusters (staphylococci)
  • 9. Bacteria Size
    • Bacteria range in size from about 0.2 to 5 um.  
    • The smallest bacteria (Mycoplasma) are the same size as a large virus.
    • The longest bacteria rods are the same size as some yeasts and human red blood cells.
  • 10. CLASSIFICATION OF BACTERIA
    • ON BASIS OF SHAPE
    • ON BASIS OF ARRANGEMENT
    • ON BASIS OF STAINING
    • ON BASIS OF OXYGEN REQUIREMENT
  • 11. MORPHOLOGY OF BACTERIA (SHAPE)
    • COCCI -- round
    • BACILLI-- rods
    • SPIROCHETES-- spiral
    • PLEOMORPHIC
  • 12. ARRANGEMENT OF BACTERIA
    • CHAINS
    • CLUSTERS
    • PAIRS
    • TETRADS
  • 13. STAINING OF BACTERIA
    • GRAM’S STAINING
    • Gram positive
    • Gram negative
    • Gram variable
  • 14. ON BASIS OF OXYGEN REQUIREMENT
    • Aerobes
    • Anaerobes
    • Facultative anaerobes
    • etc
  • 15. STRUCTURE OF BACTERIA
    • ESSENTIAL STRUCTURES
    • NON-ESSENTIAL STRUCTURES
  • 16. Essential structures
    • Cell envelope:
    • Cell wall (except Mycoplasma)
    • Cell membrane
    • Ribosome
    • Nucleoid
    • Mesosome
    • Periplasm ( in gram’s negative bacteria)
  • 17. Non Essential structures
    • Capsule
    • Pilus
    • Flagellum
    • Spore
    • Plasmid , Transposons
    • Granule
    • Glycocalyx
  • 18. Bacterial Structure
  • 19. Cell Structure
  • 20. CELL ENVELOPE
    • KEY WORDS
    • Cell envelope
    • Cell wall
    • Cell membrane
  • 21. Cell envelope
      • The cell envelope : Consists of cell membrane and cell wall plus an outer membrane if present.
      • Most bacterial cell envelopes fall into two major categories: Gram positive and Gram negative based on Gram staining characteristics that reflect major structural differences between the two groups
  • 22. GRAM POSITIVE CELL ENVELOPE Cytoplasm Lipoteichoic acid Peptidoglycan-teichoic acid Cytoplasmic membrane
  • 23. GRAM NEGATIVE CELL ENVELOPE Cytoplasm Inner (cytoplasmic) membrane Outer Membrane (Major permeability barrier) Lipopolysaccharide Porin Braun lipoprotein Periplasmic space Periplasmic binding protein Permease
  • 24. Cell Walls Depending on Structure of their cell walls, the bacteria absorb either the purple dye or the pink dye.
  • 25. Prokaryotic cell Gram + Gram - Cell wall Cell (inner) membrane Outer membrane Cell wall Cell membrane
  • 26. Cell wall
    • Cell wall consists of
    • the peptidoglycan layer
    • attached structures
    • (eg: capsule, pili etc)
  • 27.
      • PEPTIDOGLYCANS ( murein/ mucopeptide)
      • Multilayered in gram positive bacteria.
      • Surrounds the bacterial cell membrane.
      • Provides rigidity. It is huge (billions in molecular weight)
      • Consists of a glycan (polysaccharide) backbone with peptide side chains.
      • PG is found in all bacteria except Chlamydia and Mycoplasma .
  • 28.
    • Gram positive cell envelope:
    • Thick peptidoglycan with covalently bound teichoic acid . These negatively charged molecules concentrate metal ions from the surroundings. Lipoteichoic acid is primarily associated with the cell membrane .
  • 29. Gram negative cell envelope
    • Outer membrane present ( lipopolysachride, lipoprotein &phospholipid) --- endotoxin
    • Lipid A --- toxic
    • Polysaccharide core
    • Outer polysaccharide -- antigenic
    • Thin peptidoglycan layer
    • No teichoic acid
    • Periplasmic space : b/w two membranes
  • 30. Gram negative cell envelope
    • Porin protein
  • 31. GRAM POSITIVE GRAM NEGATIVE Cytoplasm Cytoplasm Lipoteichoic acid Peptidoglycan-teichoic acid Cytoplasmic membrane Inner (cytoplasmic) membrane Outer Membrane Lipopolysaccharide Porin Braun lipoprotein Periplasmic space
  • 32. Cytoplasm CELL MEMBRANE . Cell membrane
    • Oxidative phosphorylation (no mitochondria).
    • Synthesis of cell wall precursor.
    • Active transport
    • Synthesis of enzymes .
    Cell Wall
  • 33. CYTOPLASM
    • Mesosome
    • Cytoplasmic membrane invagination.
    • Cell division-----DNA binding site.
    • Ribosomes
    • 70S in size (50S & 30S)
    • Protein synthesis.
    • Nucleoid
    • No nuclear membrane.
    • DNA---Single, circular, about 2000 genes.
    • No introns in DNA, no mitotic spindle, no nucleolus, no histones
  • 34. Non Essential structures
    • Capsule
    • Pilus
    • Flagellum
    • Spore
    • Plasmid , Transposons
    • Granule
    • Glycocalyx
  • 35. Capsules and slime layers (Glycocalyx)
    • well defined: capsule
    • outside cell envelope
    • usually polysaccharide (in B. anthracis– D glutamate)
    • Gives virulance (antiphagocytic).
    • Antigenic (vaccine formation).
    • Adherence.
    • Quellung reaction (Identification).
    • not well defined-- slime layer or glycocalyx
    • Adherence
    • S.mutans (Plaque formation)
  • 36. FLAGELLA
    • For motility – long & whip like
    • Subunits—Flagellin
    • Respond to food/poison –chemotaxis
    • Never present in cocci.
    • Use ATPs – proton motive force
    • Number and location of flagella.
    • (Peritrichous, monotrichous, lophotrichous, axial).
  • 37.
    • Flagella
      • embedded in cell membrane
      • project as strand
      • Flagellin (protein) subunits
      • move cell by propeller like action
      • *axial filament
      • *flagellar antigen
  • 38. Flagella A- Monotrichous;  B- Lophotrichous; C- Amphitrichous;  D- Peritrichous;
  • 39. Axial filaments
      • spirochetes
      • similar function to flagella
      • run lengthwise along cell
      • snake-like movement
  • 40. Pili (fimbriae)
    • Short , hair-like projections of the cell
    • Protein--pilin
    • Mostly on gram-ve bacteria
    • adhesion to host epithelium
    • Two types– ordinary pili
    • sex pili
    • sexual conjugation (sex pili)
  • 41. Endospores (spores)
    • Metabolically dormant cell
    • Produced when adverse conditions eg starved – sporulation – bacterial DNA, cytoplasm, cell membrane, peptidoglycans, water & keratin- like coat
    • Resistant to adverse conditions
    • - high temperatures (not killed by boiling),
    • - radiation, dehydration
    • - organic solvents
    • Killed by autoclaving (121 C for 30 min)
    • contain dipicolinic acid
    • Bacillus (central) and Clostridium (terminal)
    • Survival for many years
  • 42. CYTOPLASM
      • Granules
      • Storage of nutrients
      • Stained with dyes
      • Transposons
    • Jumping genes – within DNA or between DNAs of bacteria, plasmids & bacteriophages
    • Pieces of DNA
    • No independent replication.
    • Can be more than one in 1 DNA.
    • For toxins, enzymes, antibiotic resistance etc.
    • 4 domains– inverted repeats, transposase, repressor, resistance.
  • 43.
    • Plasmids
    • Multiple copies in number
    • Extra-chromosomal DNA, double stranded, circular
    • Can be incorporated in DNA
    • Coding pathogenesis and antibiotic resistance, heavy metal & U-V light resistance, toxins, pili etc.
    • Replication independent of bacterial chromosome .
    • Transmissable & Non transmissable.
  • 44. Making Wall-less forms
    • Result from action of:
      • enzymes lytic for cell wall (eg lyzozyme)
      • antibiotics inhibiting peptidoglycan biosynthesis
    • Wall-less bacteria that don’t replicate:
      • spheroplasts (with outer membrane) gram - ve
      • protoplasts (no outer membrane) gram +ve.
    • Wall-less bacteria that replicate
      • L forms ( relative resistance to antibiotics)
  • 45. Naturally Wall-less Genus
    • Mycloplasma
  • 46. The Cell Envelope Gram Stain Gram Positive Gram Negative
  • 47. GRAM STAIN
    • Gram positive
    • Gram negative
    • Gram variable
  • 48. Procedure of Gram Staining
    • Developed by Christian Gram
    • In 1884
    • 4 steps:
    • Stain with Crystal voilet (primary stain)
    • Then pour Gram,s iodine (mordant)
    • Decolourize
    • Pour Safranin (counter stain)
  • 49. Gram Stain Gram negative Gram positive Heat/Dry Crystal violet stain Iodine Fix Safranin stain Alcohol de - stain
  • 50. Gram stain morphology
    • Shape
      • cocci (round)
      • bacilli (rods)
      • spiral or curved (e.g. spirochetes)
    • Single or multiple cells
      • clusters (e.g. staphylococci)
      • chains (e.g. streptococci)
    • Gram positive or negative