Morphology of Prokaryotic Cells:
Cell Shapes
Morphology of
Prokaryotic Cells:
terminology in
practice
• Curved rods:
– Campylobacter species
– Vibrio species
• Spiral rods:
– Helicobacter species
– Spirillum species
– Spirochetes:
• Leptospirosa species
Morphology of Prokaryotic Cells:
Cell Groupings
**Bacterial Structures**
You should know what all of
the structures on this diagram
are - what their basic
composition is and what their
function is
The Glycocalyx:
Capsules and Slime Layers
• Outermost layer
• Polysaccharide or
polypeptide
• May allow cells to adhere
to a surface
• Contributes to bacterial
virulence by preventing
phagocytosis
• An important virulence
factor
Filamentous Protein Appendages
Escherichia coli
Enterococcus faecium
Flagella - motility
E. coli O157:H7
Rotate like a propeller
Proton motive force used for energy
Presence/arrangement can be
used as an identifying marker
Flagella - motility
Rotate like a propeller
Proton motive force used for energy
Chemotaxis - Directed movement
towards/away from a chemical
Presence/arrangement can be
used as an identifying marker
Peritrichous
Polar
Other (ex. tuft on both ends)
Pili - attachment
Common pili (fimbriae); singular = pilus
Function in adhesion = virulence factor
Helical arrangement of protein subunits
Sex pili - Conjugation
Sharing of mobile
genetic information –
plasmids
Cell Wall
Provides rigidity to the cell
(prevents it from bursting)
Cell Wall
Provides rigidity to the cell
(prevents it from bursting)
**Cell Wall**
•Peptidoglycan - rigid molecule; unique to
bacteria
•Alternating subunits of NAG and NAM
form glycan chains
•Glycan chains are connected to each other
via peptide chains on NAM molecules
Know the basic
structure/composition of the
bacterial cell wall; know the
structureal and chemical
differences between the cell
walls of Gram-negative and
Gram-positive bacteria and how
these differences relate to how
they appear in a Gram stained
slide
Cell Wall
Cell Wall
Medical significance of peptidoglycan
•Target for selective toxicity; synthesis is
targeted by certain antimicrobial
medications (penicillins, cephalosporins)
•Recognized by innate immune system
•Target of lysozyme (in egg whites, tears)
Cell Wall
Gram-positive
Thick layer of peptidoglycan
Teichoic acids
Cell Wall
Gram-negative
Thin layer of peptidoglycan
Outer membrane - additional
membrane barrier
Lipopolysaccharide (LPS)
O antigen
Core polysaccharide
Lipid A
Cell Wall
Gram-negative
Thin layer of peptidoglycan
Outer membrane - additional
membrane barrier; porins permit passage
lipopolysaccharide (LPS)
- ex. E. coli O157:H7
endotoxin
- recognized by innate immune system
Cell Wall
Gram-negative
Thin layer of peptidoglycan
Outer membrane - additional
membrane barrier; porins permit passage
lipopolysaccharide (LPS)
periplasm
Cytoplasmic membrane
•Defines the boundary of the cell
•Semi-permeable; excludes all
but water, gases, and some
small hydrophobic molecules
•Transport proteins function as
selective gates (selectively permeable)
•Control entrance/expulsion of
antimicrobial drugs
•Receptors provide a sensor system
•Phospholipid bilayer, embedded with proteins
The Gram stain
Acid fast stains:
Fite’s, modified Fite’s, Kinyoun
Primary stain: carbolfuchsin
Decolorizing agent: acid alcohol
Secondary stain: methylene blue
Cytoplasmic membrane
•Defines the boundary of the cell
•Semi-permeable; excludes all
but water, gases, and some
small hydrophobic molecules
•Transport proteins function as
selective gates (selectively permeable)
•Control entrance/expulsion of
antimicrobial drugs
•Receptors provide a sensor system
•Phospholipid bilayer, embedded with proteins
Cytoplasmic membrane
•Defines the boundary of the cell
•Semi-permeable; excludes all
but water, gases, and some
small hydrophobic molecules
•Transport proteins function as
selective gates (selectively permeable)
•Control entrance/expulsion of
antimicrobial drugs
•Receptors provide a sensor system
•Phospholipid bilayer, embedded with proteins
Cytoplasmic membrane
•Defines the boundary of the cell
•Semi-permeable; excludes all
but water, gases, and some
small hydrophobic molecules
•Transport proteins function as
selective gates (selectively permeable)
•Control entrance/expulsion of
antimicrobial drugs
•Receptors provide a sensor system
•Phospholipid bilayer, embedded with proteins
•Fluid mosaic model
Cytoplasmic membrane
Electron transport chain - Series of proteins that eject protons from the cell,
creating an electrochemical gradient
Proton motive force is used to fuel:
•Synthesis of ATP (the cell’s energy currency)
•Rotation of flagella (motility)
•One form of transport
If a function of the cell
membrane is transport…..
• How is material transported in/out of the
cell?
– Passive transport
• No ATP
• Along concentration gradient
– Active transport
• Requires ATP
• Against concentration gradient
Types of transport
• Passive transport
• Simple diffusion
• Facilitated diffusion
• Osmosis
• Active transport
• System that uses proton motive force
• System that uses ATP
• Group translocation
Facilitated Diffusion
Diffusion of water is Osmosis
Active transport: Proton Motive
Force
Active transport: Use ATP
Active transport: Group
translocation
Internal structures: Chromosome
Internal structures: Ribosomes
Internal structures:Storage
Granules
Internal structures: Cytoskeleton
Internal structures: Endospores