Gram negative outer membrane
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Gram-Negative Outer Membrane. Figure 4.13c. Figure 4.13b–c. Thick peptidoglycan Teichoic acids In acid-fast cells, contains mycolic acid. Thin peptidoglycan No teichoic acids Outer membrane. Gram-PositiveGram-Negative Cell Walls Cell Walls. Gram-Positive Cell Walls. Teichoic acids

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Gram-Negative Outer Membrane

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Gram negative outer membrane

Gram-Negative Outer Membrane

Figure 4.13c

Gram negative outer membrane

Figure 4.13b–c

Gram positive gram negative cell walls cell walls

Thick peptidoglycan

Teichoic acids

In acid-fast cells, contains mycolic acid

Thin peptidoglycan

No teichoic acids

Outer membrane

Gram-PositiveGram-Negative Cell Walls Cell Walls

Gram positive cell walls

Gram-Positive Cell Walls

  • Teichoic acids

    • Lipoteichoic acid links to plasma membrane

    • Wall teichoic acid links to peptidoglycan

  • May regulate movement of cations.

  • Polysaccharides provide antigenic variation.

Figure 4.13b

Gram negative outer membrane1

Gram-Negative Outer Membrane

  • Lipopolysaccharides, lipoproteins, phospholipids

  • Forms the periplasm between the outer membrane and the plasma membrane.

  • Protection from phagocytes, complement, and antibiotics

  • O polysaccharide antigen, e.g., E. coli O157:H7

  • Lipid A is an endotoxin

  • Porins (proteins) form channels through membrane.

Gram stain mechanism

Gram Stain Mechanism

  • Crystal violet-iodine crystals form in cell.

  • Gram-positive

    • Alcohol dehydrates peptidoglycan

    • CV-I crystals do not leave

    • The color will be purple

  • Gram-negative

    • Alcohol dissolves outer membrane and leaves holes in peptidoglycan.

    • CV-I washes out

    • The color will be purple

Atypical cell walls

Atypical Cell Walls

  • Mycoplasmas

    • Lack cell walls

    • Sterols in plasma membrane

  • Archaea

    • Wall-less or

    • Walls of pseudomurein (lack NAM and D amino acids)

Damage to cell walls

Damage to Cell Walls

  • Lysozyme digests disaccharide in peptidoglycan.

  • Penicillin inhibits peptide bridges in peptidoglycan.

  • Protoplast is a wall-less cell.

  • Spheroplast is a wall-less Gram-positive cell.

  • L forms are wall-less cells that swell into irregular shapes.

  • Protoplasts and spheroplasts are susceptible to osmotic lysis.

Plasma membrane

Plasma Membrane

Figure 4.14a

Plasma membrane1

Plasma Membrane

  • Phospholipid bilayer

  • Peripheral proteins

  • Integral proteins

  • Transmembrane proteins

Figure 4.14b

Fluid mosaic model

Fluid Mosaic Model

  • Membrane is as viscous as olive oil.

  • Proteins move to function.

  • Phospholipids rotate and move laterally.

Figure 4.14b

Plasma membrane2

Plasma Membrane

  • Selective permeability allows passage of some molecules

  • Enzymes for ATP production

  • Photosynthetic pigments on foldings called chromatophores or thylakoids

Plasma membrane3

Plasma Membrane

  • Damage to the membrane by alcohols, quaternary ammonium (detergents), and polymyxin antibiotics causes leakage of cell contents.

Movement across membranes

Movement Across Membranes

  • Simple diffusion: Movement of a solute from an area of high concentration to an area of low concentration.

  • Facilitative diffusion: Solute combines with a transporter protein in the membrane.

Movement across membranes1

Movement Across Membranes

Figure 4.17

Movement across membranes2

Movement Across Membranes

  • Osmosis: The movement of water across a selectively permeable membrane from an area of high water concentration to an area of lower water.

  • Osmotic pressure: The pressure needed to stop the movement of water across the membrane.

Figure 4.18a

Movement across membranes3

Movement Across Membranes

Figure 4.18a–b

Gram negative outer membrane

Figure 4.18c–e

Movement across membranes4

Movement Across Membranes

  • Active transport of substances requires a transporter protein and ATP.

  • Group translocation of substances requires a transporter protein and PEP.



  • Cytoplasm is the substance inside the plasma membrane.

Figure 4.6a–b

Nuclear area

Nuclear Area

  • Nuclear area (nucleoid)

Figure 4.6a–b



Figure 4.6a–b



Figure 4.19



Figure 4.20


Metachromatic granules (volutin)

Polysaccharide granules

Lipid inclusions

Sulfur granules


Gas vacuoles


Phosphate reserves

Energy reserves

Energy reserves

Energy reserves

Ribulose 1,5-diphosphate carboxylase for CO2 fixation

Protein covered cylinders

Iron oxide (destroys H2O2)




  • Resting cells

  • Resistant to desiccation, heat, chemicals

  • Bacillus, Clostridium

  • Sporulation: Endospore formation

  • Germination: Return to vegetative state

Gram negative outer membrane

Figure 4.21b

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