Prokaryotes

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Prokaryotes

• Functional Anatomy

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Prokaryotes

• Cell walls usually peptidoglycan, a complex
  polysaccharide
• Divide by binary fission
• No internal membrane-bound organelles
• Include bacteria and archaea (no peptidoglycan)
• Unicellular

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TOPICS

• External structures
• Cell Envelope
• Internal Structures
• Cell Shapes, Arrangement, and Sizes
• Classification
• Archaea
• Biofilms

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External Structures

• Flagella
• Pili and fimbriae
• Glycocalyx

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Flagella

• Flagella (singlular flagellum)
• Composed of protein subunits
• Motility (chemotaxis)
• Varied arrangement
• Monotrichous - single flagellum
• Lophotrichous - small bunches
• Amphitrichous - both poles of the cell
• Peritrichous - randomly over cell surface

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Flagella Structure
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Chemotaxis
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Proteus vulgaris Swarming
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Axial Filament of Spirochetes

• Spirochete bacteria have their flagella embedded
  in the membrane

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Diagnostic Use of Flagella

• H antigen differs within a species and can be
  used to distinguish a serovar (serotype)
• Example E. coli O157H7 makes a potent toxin that
  causes gastroenteritis

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Fimbriae (singl. fimbria)

• Fimbriae are used for attachment
• Antibodies to fimbriae block attachment

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Pili (singl. pilus)

• Pili are used for mating (conjugation, DNA
  transmission to another cell)

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Glycocalyx

• Polysaccharide or polypeptide coat that surrounds
  cells - also called extracellular polysaccharide
  (EPS)
• Made inside cell and secreted

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Functions of Glycocalyx

• Virulence factor (disease severity)
• avoid phagocytosis (being engulfed and killed by
  white blood cells)
• Attachment to surfaces
• Syntrophic metabolism in biofilm
• Protection from drying, viruses, antibiotics
• Provide nutrients

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Capsule

• Capsule organized EPS
• tightly attached to cell wall
• Inhibits phagocytosis virulence factor

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Slime Layer (EPS)

• Slime layer unorganized, loosely attached to
  cell wall
• Attachment, blocks phagocytosis

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Biofilms

• Biofilm a microbial community attached to a
  surface
• May be one or several organisms

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Environmental Biofilms
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Environmental Biofilms
What do cows and termites have in common?
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Environmental Biofilms
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Infectious Disease Biofilms
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Infectious Disease Biofilms

• On implants

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Some Medically Important Biofilms

• CDC estimate 65 of human bacterial infections
• Dental plaque
• Infectious kidney stones
• Endocarditis
• Catheters
• Cystic Fibrosis

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Cell Envelope

• Cell Wall
• classification
• shape
• Cytoplasmic (plasma) membrane

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Cell Wall

• Located just outside plasma membrane
• Functions
• maintains cell shape
• protects cell from rupturing when water pressure
  is higher inside cell
• anchors flagella
• Differentiated by Gram stain

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Peptidoglycan (PG)

• Repeating disaccharide of N-acetylglucosamine
  (NAG) and n-acetylmuramic acid (NAM)
• Cross linked by polypeptides
• Penicillin blocks peptidoglycan cross-linking
• Lysozyme breaks peptidoglycan

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Gram Positive Cell Wall

• Many layers of peptidoglycan
• Teichoic acid
• Regulate positive ion flow
• Protect wall from breakdown
• Antigen specificity of cells

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http//www.arches.uga.edu/kristenc/cellwall.html
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Gram Negative Cell Wall

• Thin peptidoglycan, no teichoic acid
• Outer membrane (OM) contains lipopolysaccharide
  (LPS) endotoxin ( O antigen)
• Protects cell from penicillin, lysozyme
• Contains porins that form channels to allow
  passage of nutrients

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LPS
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Gram Positive and Negative Cell Walls
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Cytoplasmic membrane

• Lipid bilayer
• Phospholipids
• Proteins
• Functions
• Regulates transport
• Site of ATP synthesis

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Atypical Cell Walls

• Mycobacteria (TB, leprosy)
• Very thick outer lipid layer - acid fast
• Slow nutrient exchange
• Slow growth

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Atypical Cell Walls

• Mycoplasma lack cell wall - pleiotropic

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Damage to Cell Walls

• Digested by lysozyme
• Gram positive bacteria become protoplasts, lyse
  in distilled water by osmotic lysis
• Gram negative cells become spheroplasts

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To Be Continued

• Internal Structures
• Cell shapes and arrangements
• Classification
• Archaea