Microbial Growth And Requirements

• Classification

  • Acidophile
  • Neutrophile
  • Alkaliphile
• Psychrotrophs


  • Microorganisms that can grow at cold temperatures but have an optimal growth temperature higher than psychrophiles
• Physical Requirements

  • Temperature
  • pH
• Thermophiles


  • Microorganisms that thrive in high temperatures
• Mesophiles


  • Microorganisms that grow optimally at moderate temperatures
• Psychrophilic microorganisms


  • Polaromonas, Chlamydomonas nivalis
• Neutrophiles have a pH range of >5.5 and <8, with an example being E. Coli
• Acidophiles have a pH range of <5.5, with examples like Rhodopila globoformis, Acidithiobacillus ferrooxidans, Picrophilus oshimae
• Psychrophiles


  • Microorganisms that thrive in cold temperatures
• Alkaliphiles have a pH of 8, with an example being Chloroflexus aurantiacus
• Thermophilic microorganisms


  • Methanopyrus, Synechococcus, Thermus aquaticus
• Organisms able to live in environments high in sugar as a solute are called OSMOPHILES
• Oxygen level requirement groups

  • Obligate Aerobe
  • Facultative Anaerobe
  • Microaerophile
  • Aerotolerant Anaerobe
  • Obligate Anaerobe
• Bacterial Division methods

  • Binary fission
  • Budding
• pH classifications

  • Acidophile
  • Neutrophile
  • Alkaliphile
• Chemical Requirements

  • Carbon
  • Nitrogen
  • Sulfur
  • Phosphorous
  • Trace Elements
  • Organic Growth Factors
• Organisms able to grow in very dry environments (made dry by lack of water rather than from dissolved solutes) are called XEROPHILES
• Slime layers composed of bacterial communities found in surfaces such as rock in a pond, human tooth, or mucous membrane
• Organisms according to required pH level

  • Neutrophile (pH >5.5 and <8)
  • Acidophile (pH <5.5)
  • Alkaliphile (pH 8)
• Oxygen level requirements

  • High O2 level
  • Low O2 level
• Generation Time Formula: Generation Time = Nf is the total number of cel
• Phases of Growth

  • Lag phase
  • Log phase
  • Stationary phase
  • Death phase
• Formula: Generation Time Nf is the total number of cells in the population Ni is the starting number of cells. Exponent n denotes generation time. 2^n is the number of cells in that generation. Nf = (Ni)2^n
• References: 'Tortora, G. J., Funke, B. R. & Case, C. L. (2016). Microbiology; An Introduction. 12th ed. Boston: Pearson Publisher. Madigan, M. T., Martinko, J. M., Stahl, D. A. & Clark, D. P. (2010). Brock Biology of Microorganisms. 13th ed. Benjamin Cummings Publisher'
• Bacterial Division

  • Binary fission
  • Budding
• Spectrophotometer used in measuring turbidity