PPT 2 (SLIDE 1-51)

• Environmental Effects on Bacterial Growth

  • Temperature
  • pH
  • Osmotic pressure
  • Oxygen classes
• Cardinal Temperatures

  1. Minimum
  2. Optimum
  3. Maximum
• Minimum Temperature

  • Temperature below which growth ceases, or lowest temperature at which microbes will grow.
• Optimum Temperature

  • Temperature at which its growth rate is the fastest.
• Maximum Temperature

  • Temperature above which growth ceases, or highest temperature at which microbes will grow.
• Mesophiles (20-45C)

  • Midrange temperature optima
  • Found in warmblooded animals and in terrestrial and aquatic environments in temperate and tropical latitudes
• Psychrophiles (0-20C)

  • Cold temperature optima
  • Most extreme representatives inhabit permanently cold environments
• Hyperthermophiles

  • Optima greater than 80C
  • These organisms inhabit hot environments
• pH

  • measure of [H+] each organism has a pH range and a pH optimum
• acidophiles

  • optimum in pH range 1-4
  • organisms that grow best at low pH
• alkalophiles

  • optimum in pH range 8.5-11
  • organisms that grow best at high pH
• 1. lactic acid bacteria - 4-7
  2. Thiobacillus thiooxidans – 2.2-2.8
  3. fungi – 4-6
• Most of pathogenic bacteria are neutrophiles
• Osmotic pressure depends on the surrounding solute concentration and water availability
• osmophiles

  • organisms which thrive in high solute
• osmotolerant

  • organisms which tolerate high solute
• Halophile

  • organisms which thrive in high salt
• Halotolerant

  • organisms which tolerate high salt
• Barophiles

  • organisms which thrive in high pressure
• Barotolerant

  • organisms which tolerate high pressure
• Xerophiles

  • are able to grow in very dry environments
• Macronutrients

  • elements required in fairly large amounts
• Micronutrients

  • metals and organic compounds needed in very small amounts
• Enzyme for organisms that lives or required O2

  1. catalase (or peroxidase)
  2. Superoxide dismutase (SOD)
• Superoxide Dismutase

  • converts O2 - into H2O2 and O2
• Catalase

  • breaks down H2O2 into H2O and O2
• Obligate aerobes

  • require O2 in order to grow
• Obligate anaerobes

  • cannot survive in O2
• • Facultative anaerobes

  • grow better in O2
• Aerotolerant

  • organisms don’t care about O2
• Microaerophiles

  • require low levels of O2
• Test for Oxygen Requirements of Microorganisms

  • Thioglycolate Broth
• Thioglycolate Broth

  • Contains a reducing agent and provides aerobic and anaerobic conditions
• Thioglycolate 2 Zone

  1. Oxic Zone
  2. Anoxic Zone
• Obligate Anaerobes

  • SOD - positive
  • Catalase - positive
• Facultative anaerobes enzyme

  • SOD - positive
  • Catalase - positive
• Aerotolerant anaerobes

  • SOD - positive
  • Catalase - negative
• Strict Anaerobes

  • SOD - negative
  • Catalase - negative
• Microaerophiles

  • SOD - positive
  • Catalase - low levels
• Culture media

  • supply the nutritional needs of microorganisms