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Dr. Alvin Fox

Bacterial cell, Lecture 32. Dr. Alvin Fox. Archaebacteria . ( Archaea ). Key Words. Prokaryotic. Outer membrane . Eubacteria ( Bacteria ) . Periplasmic space. Oxidative phosphorylation . Eukaryotic. Spheroplast/protoplast . Plasmid.

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Dr. Alvin Fox

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  1. Bacterial cell, Lecture 32 Dr. Alvin Fox

  2. Archaebacteria (Archaea) Key Words Prokaryotic Outer membrane Eubacteria (Bacteria) Periplasmic space Oxidative phosphorylation Eukaryotic Spheroplast/protoplast Plasmid Flagella Chromosome Chemotaxis Ribosome Axial filament Peptidoglycan (murein, mucopeptide) Periplasmic binding protein Gram stain Permeases Gram negative Storage Granules Gram positive Pili (fimbriae) Cell envelope Capsule (slime layer, glycocalyx) Cell membrane Endospore (spore) Cell wall

  3. EUKARYOTES PROKARYOTES BACTERIA ARCHAEA

  4. Prokaryotes (Bacteria) • Eubacter "True" bacteria • human pathogens • clinical or environmental • one kingdom • Archaea • Environmental organisms • second kingdom

  5. Eukaryotes • Other cell-based life e.g. • plants • animals • fungi

  6. Prokaryotic Cell (versus Eukaryotic Cell) • Not compartmentalized • Cell membranes lack sterols (e.g. cholesterol) • Single circular chromosome • Ribosomes - 70S - subunits • 30S (16S rRNA) • 50S (5S & 23S rRNA)

  7. Bacteria versus Archaebacteria • Eubacteria • peptidoglycan (murein) • muramic acid • Archaebacteria • pseudomurein • no muramic acid

  8. Bacteria versus Archaebacteria • 16S rRNA • sequence different

  9. Eukaryotic cell Prokaryotic cell Gram + (e.g. animal) Flagellum Nucleoid Cell membrane Cell wall Rough endoplasmic reticulum Nucleus Gram - Pili Granule Capsule Cytoplasm Cell (inner) membrane Outer membrane Ribosomes Mitochondria Cell wall

  10. Bacteria • Plasmids • Extra-chromosomal DNA • multiple copy number • coding • - pathogenesis factors • - antibiotic resistance factors • bacterial replication

  11. The Cell Envelope Gram Stain Gram Positive Gram Negative

  12. Oxidative phosphorylation occurs at cell membrane (since there are no mitochondria). Cell Wall Cytoplasm Cell membrane • The cell wall is outside of cell membrane • rigid, protecting cell from osmotic lysis.

  13. GRAM POSITIVE Lipoteichoic acid Peptidoglycan-teichoic acid Cytoplasmic membrane Cytoplasm GRAM NEGATIVE Lipopolysaccharide Porin Outer Membrane Braun lipoprotein Periplasmic space Inner (cytoplasmic) membrane Cytoplasm

  14. Outer Membrane • Gram negative bacteria • major permeability barrier • space between inner and outer membrane • periplasmic space • store degradative enzymes • Gram positive bacteria • no periplasmic space

  15. GRAM NEGATIVE CELL ENVELOPE Outer Membrane (Major permeability barrier) Lipopolysaccharide Porin Braun lipoprotein Periplasmic space Degradative enzyme Periplasmic binding protein Permease Inner (cytoplasmic) membrane Cytoplasm

  16. GRAM POSITIVE CELL ENVELOPE Degradative enzyme Peptidoglycan-teichoic acid Lipoteichoic acid Cytoplasmic membrane Cytoplasm

  17. FLAGELLA • Some bacteria are motile • Locomotory organelles- flagella • Taste environment • Respond to food/poison • chemotaxis

  18. Flagella • embedded in cell membrane • project as strand • Flagellin (protein) subunits • move cell by propeller like action

  19. Axial filaments • spirochetes • similar function to flagella • run lengthwise along cell • snake-like movement

  20. Making Wall-less forms • Result from action of: • enzymes lytic for cell wall • antibiotics inhibiting peptidoglycan biosynthesis • Usually non-viable • Wall-less bacteria that don’t replicate: • spheroplasts (with outer membrane) • protoplasts (no outer membrane). • Wall-less bacteria that replicate • L forms

  21. Naturally Wall-less Genus • Mycoplasma

  22. Pili (fimbriae) • hair-like projections of the cell • sexual conjugation • adhesion to host epithelium

  23. Capsules and slime layers • outside cell envelope • well defined: capsule • not defined: slime layer or glycocalyx • usually polysaccharide • often lost during in vitro culture • protective in vivo

  24. Endospores (spores) • Dormant cell • Produced when starved • Resistant to adverse conditions • - high temperatures • - organic solvents • contain calcium dipicolinate • Bacillus and Clostridium

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