Exam 3

• Reading Phylogenetic trees

  A) Node

  B) Sister groups

  C) Outgroup

  
• Bacteria General characteristics :

  Micro organisms : 0.5 - 2.0 um in size

  Prokaryotic , single celled

  DNA : single circular chromosome and small circular plasmids
• Bacteria lack complex compartmentalization

  • in growths of plasma membrane that perform metabolic function
• Bacteria can contain gas vessels

  Gas Vessels : capsules containing gas

  • Helps to float (in water) to get closer to surface (sunlight)
• Cell wall : rigid

  • cell shape , physical protection, prevents lysis in a hypotonic environment
  • peptidoglycan (polypeptides + sugars) (lacking is archaea)
• Three shapes for bacteria

  1. Cocci
  2. bacilli
  3. Spiral
• Another shape for bacteria could also be comma shaped rod
• Gram stain tech : groups bacteria by cell wall

  composition of G+ and G-
• G+

  1. plasma membrane
  2. thick peptidoglycan layer
• G-

  1. Plasma membrane
  2. thin peptidoglycan layer
  3. outer member + lipopolysaccharide
• G+ crystal violet :

  stains thick peptidoglycan deep purple
• G-

  alcohol removes crystal violet

  Safrinin counterstain makes cell pink
• Against antibiotics

  G+

  More sensitive to antibiotics (inhibit cell wa;; formation)

  G-

  double membrane resistant to drugs
• Glycocalyx

  Capsule : more dense, firmly attached

  or slime layer : more loosely attached

  'mucilage' : hydrated polysaccharides and proteins, lipids and nucleic acids (biofilm)
• Fimbriae : proteinaceous filament for attachment
• Biofilm: a thin but robust layer of mucilage adhering to a solid surface and containing a community of bacteria and other microorganisms.
• Motility : may have flagella

  Taxis : moves towards stimulus
• Bacterial (archaea) reproduction :

  1. Binary fission (no spindle) : Simple cell division (similar to mitosis)
  2. Budding : unequal division
• Bacterial genetic exchange :

  1. Conjugation
  2. transformation
  3. transduction
• Horizontal gene transfer : DNA exchanged between different species
• Conjugation : via pilus or "mating bridge"

  F factor : genes which allow cell to form pili and donate plasmids of chromosomal DNA
• F+ can form pilus, F- cannot

  Though, can acquire F factor gene after going through conjugation with an F+