Micro Exam 2

• What determines microbial growth?

  An increase in the number of cells NOT the size of the individual cells
• 3 Physical requirements for microbial growth

  1. Temp
  2. Ph
  3. Osmotic Pressure
• The lowest temp at which an organism can survive and replicate is

  minimum growth
• The growth rates are the highest at

  optimum growth
• The highest temp at which organisms can survive and replicate is

  maximum growth
• What are psychrophiles

  Survive in : Polar Region

  Temp : -10 - 20 C
• What are Psychotrophs

  Spoilage in refrigerated foods

  Temp : -10 - 20 C
• What are Mesophiles

  Most pathogens and spoilage organisms

  Temp: 10 - 50 C
• What are Thermophiles

  Location : Compost Piles & Spoilage of Canned Goods

  Temp: 40 - 70 C
• What are Hyperthermophiles

  Location: Hydrothermal Vents & Hot Springs

  Temp: 65 - 110 C
• Danger Zone

  15 - 50 C
• Rapid growth of bacteria; some may produce toxins

  Danger Zone
• Major reason of illnesses

  improper cooling
• Primary reason for food related illnesses

  leaving cooked foods out for too long
• Room Temperature is

  78 F / 25 C
• The boiling point of water is

  212 F / 100 C
• Ice Forms at

  32 F / 0 C
• Osmosis

  Movement of water from high concentration to a low concentration
• Isotonic Solutions

  Equal concentration both inside and outside of cell
• Hypertonic Solutions

  Little concentration inside cell ; shrivels
• Hypotonic Solutions

  Too much concentration inside cell ; swells and bursts
• Obligate


  Required Condition
• Facultative

  Can tolerate conditions for a short period of time
• Heterotrophs

  Use organic carbon sources
• Autotrophs

  Use CO2 to make sugars
• 4 Major chemical elements required for all bacterial growth

  1. Carbon
  2. Nitrogen
  3. Sulfur
  4. Phosphorus
• Trace Elements

  Inorganic elements required in small amounts
• 4 Examples of trace elements

  1. Iodine
  2. Magnesium
  3. Zinc
  4. Iron
• 4 Toxic Forms of oxygen

  1. Superoxide Free Radicals
  2. Peroxide Anion
  3. Singlet Oxygen
  4. Hydroxyl Radical
• Superoxide Dismutase

  O2- + 2H+ ----> H2O2 + O2
• Catalase

  2H2O2 ----> 2H2O + O2
• Peroxidase

  H2O2 + 2O+ ----> 2H2O
• What are vitamin, amino acids, purines, and pyrimidines ?

  Organic compounds obtained from the environment
• Culture

  Microbes growing in / on culture medium
• Culture Medium

  Nutrients prepared for microbial growth
• Sterile

  No living microbes, including endospores
• Inoculum

  Voluntary introduction of microbes into medium
• Contamination

  Involuntary introduction of microbes into medium
• 4 Types of culture media

  1. Broth
  2. Agar Slant
  3. Agar Deep
  4. Agar Plate
• Why might a microbiologist choose one media over the other?

  To only culture the desired bacteria