Topic 5: factors of growth

• Factors in the environment

  • Availability of nutrients
  • Interaction with organisms
  • Physical and chemical controls
• Physical conditions


  Temperature and pressure
• Chemical conditions


  Salinity, oxygen and pH
• Oxygen


  Anaerobes inhibited by obligate anaerobes
• Toxic forms of oxygen
• Different incubation under anoxic conditions

  • Gas jar
  • Anaerobic chamber
  • Vessels
• Temperature


  Major environmental factor
• Organisms based on optimal temperature conditions

  • Psychrophile - below 15
  • Mesophile - around 20-50 (medically significant)
  • Thermophile - around 40-80
  • Hyperthermophile - above 80
• Organisms based on pH preferences

  • Acidophilus - like acidic conditions (pH 6)
  • Alkaliphile - like alkaline conditions (pH 8)
• Other organism types


  • Osmophile - high sugar concentration
  • Xerophile - dry environment
  • Barophile/piezophile - high pressure
  • Barotolerant - grow in absence of pressure but with pressure
  • Obligate aerobe - need oxygen
  • Obligate anaerobe - doesn't require oxygen and is killed by it
  • Facultative - can grow with or without oxygen
  • Microaerophile - uses oxygen at low atmospheric concentrations
  • Aerotolerant - tolerant of oxygen but doesn't use it
• Organisms from least to highest temperature

  • Psychrophile
  • Mesophile
  • Thermophile
• Cold adaptation


  • Wants flexibility
  • Enzymes have more alpha helix sheets
  • Cytoplasmic membrane has increased unsaturated and shorter fatty acids
  • Cryoprotectants
• Hot adaptation


  • Wants stability
  • Enzymes and proteins modified
  • Cytoplasmic membrane modified
  • Bacteria have more saturated lipids
  • Archaea have monolayer membranes