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

Rotate like a propeller Proton motive force used for energy Presence/arrangement can be used as an identifying marker Flagella - motility E. coli O157:H7

Flagella - motility Presence/arrangement can be used as an identifying marker Peritrichous Polar Other (ex. tuft on both ends) Rotate like a propeller Proton motive force used for energy Chemotaxis - Directed movement towards/away from a chemical

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 Glycan chains are connected to each other via peptide chains on NAM molecules Alternating subunits of NAG and NAM form glycan chains 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

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) endotoxin - recognized by innate immune system - ex. E. coli O157:H7

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 Transport proteins function as selective gates (selectively permeable) Control entrance/expulsion of antimicrobial drugs Receptors provide a sensor system Semi-permeable; excludes all but water, gases, and some small hydrophobic molecules 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

Defines the boundary of the cell Transport proteins function as selective gates (selectively permeable) Control entrance/expulsion of antimicrobial drugs Receptors provide a sensor system Semi-permeable; excludes all but water, gases, and some small hydrophobic molecules Phospholipid bilayer, embedded with proteins Cytoplasmic membrane

Defines the boundary of the cell Transport proteins function as selective gates (selectively permeable) Control entrance/expulsion of antimicrobial drugs Receptors provide a sensor system Semi-permeable; excludes all but water, gases, and some small hydrophobic molecules Phospholipid bilayer, embedded with proteins

Cytoplasmic membrane Defines the boundary of the cell Transport proteins function as selective gates (selectively permeable) Control entrance/expulsion of antimicrobial drugs Receptors provide a sensor system Semi-permeable; excludes all but water, gases, and some small hydrophobic molecules Phospholipid bilayer, embedded with proteins Fluid mosaic model

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 Cytoplasmic membrane Electron transport chain

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