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TORTORA  FUNKE  CASE
ninth edition
MICROBIOLOGY
an introduction
4
Part A
Functional
Anatomy of
Prokaryotic and
Eukaryotic Cells
PowerPoint® Lecture Slide Presentation prepared by Christine L. Case
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Prokaryotic Cells
 Comparing prokaryotic and eukaryotic cells
 Prokaryote comes from the Greek words for
prenucleus.
 Eukaryote comes from the Greek words for
true nucleus.
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Prokaryote
Eukaryote
 One circular
 Paired chromosomes,
chromosome, not in a
in nuclear membrane
membrane
 No histones
 Histones
 No organelles
 Organelles
 Peptidoglycan cell walls
 Polysaccharide cell walls
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Prokaryotes
 Average size: 0.2 -1.0 µm  2 - 8 µm
 Basic shapes:
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Figures 4.1a, 4.2a, 4.2d, 4.4b, 4.4c
Prokaryotes
 Unusual shapes
 Star-shaped Stella
 Square Haloarcula
 Most bacteria are monomorphic
 A few are pleomorphic
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Figure 4.5
Arrangements
 Pairs: Diplococci,
diplobacilli
 Clusters: Staphylococci
 Chains: Streptococci,
streptobacilli
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Figures 4.1a, 4.1d, 4.2c
Main bacterial shapes
 Cocci
 Bacillus
 Coccobacillus
 Spirochete
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Glycocalyx (Sugar Coat)
 Outside cell wall
 Usually sticky
 A capsule is neatly organized
 A slime layer is unorganized
and loose
 Extracellular polysaccharide
allows cell to attach
 Capsules prevent phagocytosis
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Figure 4.6a–b
Glycocalyx and virulence
 Capsules are present and are there to protect the
bacteria from phagocytosis by the host.
 In some species – only the encapsulated bacteria will
cause disease (B. anthracis)
 Why would non-capsulated cells not be able to cause
disease?
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Flagella
 Outside cell wall
 Made of chains of
flagellin
 Attached to a protein
hook
 Anchored to the wall
and membrane by the
basal body
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Figure 4.8a
Flagella
 Three main parts
 Filament – long outermost region, contains flagellin
in intertwining chains to form a helix around a hollow
core (no membrane or sheath protecting them)
 Hook – the filament is attached here
 Basal body – anchors the flagellum to the cell wall /
plasma membrane
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Flagella Arrangement
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Figure 4.7
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Figure 4.8b
Motile Cells
 Rotate flagella (either clockwise or counter-clockwise)
to run or tumble
 Eukaryotic flagella move with more wavelike
appearance.
 Motility – ability of an organism to move by itself
 Move toward or away from stimuli (taxis)
 Flagella proteins are H antigens
(e.g., E. coli O157:H7) *useful to determine among
serovars / variations in a species
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 Different types of taxis (movement toward or away from
a stimulus)
 Chemotaxis
 Phototaxis
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Motile Cells
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Figure 4.9
Motile Cells
PLAY
Animation: Bacterial Motility
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Figures 4.9a, 4.23d
Axial Filaments
 Endoflagella
 In spirochetes
 Anchored at one end
of a cell
 Rotation causes cell
to move
 Bundles of fibrils at the
end of a cell
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Figure 4.10a
Axial filaments
 Treponema pallidum (causative agent of syphillis)
 Borrelia burgdorferi (c / a of Lyme disease)
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 Fimbriae allow
attachment
 Pili are used to
transfer DNA from
one cell to another
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Figure 4.11
Cell Wall
 Prevents osmotic lysis
 Made of peptidoglycan (in bacteria)
 Almost all prokaryotes have a cell wall
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Figure 4.6a–b
Peptidoglycan
 Polymer of disaccharide
N-acetylglucosamine (NAG) and N-acetylmuramic acid
(NAM)
 Linked by polypeptides
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Figure 4.13a
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Figure 4.13b–c
Gram-Positive
Cell Walls
Gram-Negative
Cell Walls
 Thick peptidoglycan
 Thin peptidoglycan
 Teichoic acids
 lipopolysaccharide
 In acid-fast cells,
 No teichoic acids
contains mycolic acid
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 Outer membrane
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.
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Figure 4.13b
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.
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Gram-Negative Outer Membrane
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Figure 4.13c
Gram Stain Mechanism
 Crystal violet-iodine crystals form in cell.
 Gram-positive
 Alcohol dehydrates peptidoglycan
 CV-I crystals do not leave
 Gram-negative
 Alcohol dissolves outer membrane and leaves holes
in peptidoglycan.
 CV-I washes out
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Atypical Cell Walls
 Archaea
 Wall-less or
 Walls of pseudomurein (lack NAM and D amino
acids)
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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.
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Plasma Membrane
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Figure 4.14a
Plasma Membrane
 Phospholipid bilayer
 Peripheral proteins
 Integral proteins
 Transmembrane proteins
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Figure 4.14b
Fluid Mosaic Model
 Membrane is as viscous as olive oil.
 Proteins move to function.
 Phospholipids rotate
and move laterally.
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Figure 4.14b
Plasma Membrane
 Selective permeability allows passage of some
molecules
 Enzymes for ATP production
 Photosynthetic pigments on foldings called
chromatophores or thylakoids
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Plasma Membrane
 Selective permeability
 AKA – semipermeability
 Mesosomes – Originally thought to be a cell structure
(large irregular folds in the plasma membrane),
scientists even proposed many functions…. But… we
have figured out they are not cell structures at all, just
an artifact from preparing the specimen
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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.
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Movement Across Membranes
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Figure 4.17
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.
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Figure 4.18a
Movement Across Membranes

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Figure 4.18a–b
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Figure 4.18c–e
Movement Across Membranes
 Active transport of substances requires a transporter
protein and ATP.
 Group translocation of substances requires a
transporter protein and PEP.
PLAY
Animation: Membrane Transport
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Cytoplasm
 Cytoplasm is the substance inside the plasma
membrane.
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Figure 4.6a–b
Nuclear Area
 Nuclear area (nucleoid)
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Figure 4.6a–b
Ribosomes
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Figure 4.6a–b
Ribosomes
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Figure 4.19
Inclusions
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Figure 4.20
Endospores
 Resting cells
 Resistant to desiccation, heat, chemicals
 Bacillus, Clostridium
 Sporulation: Endospore formation
 Germination: Return to vegetative state
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Figure 4.21b