MICB Lecture 5

• Family, molecular, how long

  circular, single stranded RNA molecule

  family: pospiviroidae (replicate in nucleus)

  250-430 nucleotides long

  
• Which is which

  PrPsc differs from PrPc in its 3 dimensional conformation, it is stable and aggregates with other PrPsc

  A) PrPc

  B) PrPsc

  
• eukaryotic microbes exhibit both sexual and asexual reproduction
• Prokaryotic microbes reproduce asexually through binary fission
• FtsZ

  a key bacterial cytoskeletal protein in bacteria and archaea
• FtsZ features

  Homologue of eukaryotic protein tubulin

  required for cell division and septum formation

  forms contractile ring at midcell

  energy from hydrolysis of GTP
• batch culture

  closed vessel (test tube or flask), single batch of medium, population growth can be observed when microbes are cultivated in this
• What is this

  Bacterial growth curve

  A) lag phase

  B) exponential phase

  C) stationary phase

  D) death phase

  
• lag phase


  period following intro of microorganisms into fresh culture

  • no growth - cells synthesizing new components
  • can differ
• exponential phase 


  balanced, constant growth

  2, 4, 8, 16, 32

  growth expressed as generation (doubling time): time required for cells to divide
• stationary phase

  Population growth ceases due to

  • carrier capacity
  • lack of oxygen
  • toxic biproducts
• Death phase

  nutrient deprivation and buildup of toxic wastes cause irreparable harm to cells
• Spores

  stress resistant, dormant cells

  forms when mother cell lysis

  A) bacillus

  
• Name/disease

  Clostridium tetani

  causes tetanus, spores form at one pole

  
• direct cell counts

  measures microbial growth

  Petroff-Hausser method of counting chambers

  drawback: overestimate cell count
• Viable cell counts - measuring microbial growth

  Plating - colony forming units, combine with turbidity measurements
• turbidity measurements - measuring microbial growth

  microbial cells scatter when light strikes them

  more turbid = more cells = more light scattered = higher absorbance reading on spectrophotometer