Cells

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Cells

• Prokaryotic
• No nucleus DNA free in cytoplasm
• No internal membranes
• Small size
• Bacteria

• Eukaryotic
• Membrane bound nucleus
• Internal membranes
• Larger
• Protists, Fungi, Plants, and Animals

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Glycocalyx

• Most, if not all, bacteria have glycocalyx
• Usually carbohydrate, sometimes protein
• Adhesion, biofilm formation, protection
• Loose slime tight capsule

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Movement

• Simple flagella
• Protein- flagellin H antigen
• Polar, peritrichous, lophotrichous
• Filament
• Filament, Hook,and Basal body
• Powered by Proton Motive Force
• Runs and tumbles
• Chemotaxis movement toward or away

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Motile Cells
Figure 4.9
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Axial Filaments

• Endoflagella
• In spirochetes
• Anchored at one end of a cell
• Rotation causes cell to move
• Corkscrew movement

Figure 4.10a
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Pili and Fimbriae

• Short protein projections
• Fimbriae allow attachment
• Pili are used to transfer DNA from one cell to
  another

Figure 4.11
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Cell Wall

• Determines shape
• Prevents osmotic lysis
• Contains peptidoglycan (in bacteria)

Figure 4.6a, b
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Cell wall

• Peptidoglycan unique to bacteria
• Polymer of modified glucose molecules
• N-acetyl muramic acid
• N-acetyl glucosamine
• Linked by peptides in 3-D structure
• Entire cell wall covalently bound

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Cell Walls

• Gram positive Thick layer of peptidoglycan,
  with teichoic acids
• Gram negative thin layer of peptidoglycan with
  outer membrane
• Outer membrane contains lipopolysaccharide
• Lipid A, core polysaccharide, O antigen
• Porins allow transport of material into cell

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Figure 4.13b, c
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Gram-Positive cell walls

• Teichoic acids
• Lipoteichoic acid links to plasma membrane
• Wall teichoic acid links to peptidoglycan
• May regulate movement of cations
• Teichoic acids provide antigenic variation

Figure 4.13b
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Gram-Negative Outer Membrane

• Lipopolysaccharides, lipoproteins, phospholipids.
• Periplasm forms between the outer membrane and
  the plasma membrane.
• Protection from phagocytes, complement,
  antibiotics.
• O polysaccharide antigen, e.g., E. coli O157H7.
• Lipid A is an endotoxin.
• Porins (proteins) form channels through membrane

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Atypical Cell Walls

• Mycoplasmas
• Lack cell walls
• Sterols in plasma membrane
• 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 Gram negative 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
Figure 4.14a
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Cell Membrane

• Limit of cell
• Phospholipid bilayer with embedded proteins
• Fluid mosaic model
• Enzymes for ATP production
• Photosynthetic pigments on foldings called
  chromatophores or thylakoids

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Plasma Membrane

• Phospholipid bilayer
• Peripheral proteins
• Integral proteins
• Transmembrane proteins

Figure 4.14b
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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.
• Osmosis Movement of water across a selectively
  permeable membrane from an area of high water
  concentration to an area of lower water.
• Facilitative diffusion Solute combines with a
  transporter protein in the membrane.

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Figure 4.18c-e
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Movement Across Membranes

• Active transport of substances requires a
  transporter protein and ATP.
• Group translocation of substances requires a
  transporter protein and Phosphate source.

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DNA

• Chromosome
• Nucleoid
• Single, circular molecule of DNA
• Controls functions of cell
• Genetic material
• Plasmids
• Small circular DNA
• Can be passed to other cells
• Genes for non-essential functions

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Nuclear Area

• Nuclear area (nucleoid)

Figure 4.6a, b
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Cytoplasmic Components

• Ribosomes
• Inclusions
• Beta hydroxybutarate
• Sulfur granules
• Metachromatic granules
• Not bound by phospholipid membranes
• Liquid solution of chemicals

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Ribosomes
Figure 4.19
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Inclusions

• Metachromatic granules (volutin)
• Polysaccharide granules
• Lipid inclusions
• Sulfur granules
• Carboxysomes
• Gas vacuoles
• Magnetosomes

• Phosphate reserves
• Energy reserves
• Energy reserves
• Energy reserves
• Ribulose 1,5-diphosphate carboxylase for CO2
  fixation
• Protein covered cylinders
• Iron oxide (destroys H2O2)

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Endospores

• Dormant, resistant form
• One cell one spore one cell
• Section of cell walled off, dehydrated
• Resistant to heat, chemicals, radiation
• Germinate in favorable conditions

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Shapes

• Cocci
• Singly, diplo-, strepto-, staphylo-
• Bacilli
• Curved rods
• Spirals
• Spirillum and spirochetes
• Stalked
• Branched

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Classification

• Morphology
• Cells and colonies
• Chemistry
• Biochemical reactions
• Serology
• Antigen-antibody reactions
• Genetic and molecular analysis
• GC composition of DNA
• rRNA nucleic acid sequencing

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