Microbial Growth

  1. Microbial growth refers to
    • Increase in number of cells and not cell size
    • Eg. Increase in populations or colonies 
  2. Physical requirements to microbial growth
    • Temperature
    • pH
    • Osmotic Pressure
  3. Chemical requirement for microbial growth
    • Carbon
    • Nitrogen, sulfur, and phosphorous 
    • Trace elements
    • Oxygen
    • Organic growth factors
  4. Minimum growth temp
    The lowest temp at which an organism will grow
  5. Optimum growth pattern
    The temp at with an organism grows best
  6. Maximum growth temp
    The highest temp an organism with grown in
  7. Organisms classified on a basis of their preferred temp rang
    • Psychrophiles
    • Mesophiles 
    • Thermophiles
  8. Psychotrophs
    • Can grow at 00C but optimal growth at 20-30 (refrigeration temp, similar to psychrophiles 
    • So sensitive to heat they may not grown at warm room temp (25oC)
    • Usually found in oceans depths/polar regions
    • Food Spoilage
  9. Mesophiles
    • Optimal growth of  25-45oC
    • Most common type of microbe
    • Live in the bodies on animals and usually have an optimal growth closer to the temp of the host
    • Most common disease components
  10. Thermophiles
    • High temperatures (50-60oC)
    • About the temp of hot tap water
    • Endospores formed help survive in higher heat
  11. Hyperthermophiles
    • Aka extreme thermophiles 
    • Hot springs associated volcanic activity
    • Sulfur is usually important in their metabolic activity 
    • Deep sea hydrothermal vents (121oC)
  12. Organism classifications based on pH
    • Acidophile
    • Neutrophile 
    • Alkalineophile
  13. Acidophile
    Grow in acidic or low pH environments
  14. Neutrophile
    • Most bacteria grow best at neutral 6.5-7.5pH
    • Which is about the same pH range as most tissues and organs
  15. pH in which most molds and yeast grow
    Between pH or 5-6
  16. Alkalinophiles
    Organisms that grow best in alkaline environments
  17. Plasmolysis
    Is osmotic loss of water, causing shrinkage of cell's cytoplasm
  18. Hypertonic environments
    • Water from the cell passes through the plasma membrane and into the hypertonic/ High [solute] solution.
    • Can be used to preserve foods 
    • Plasmolysis 
  19. Extreme/Obligate Halophiles
    When the organisms require environment with high salt concentrations
  20. Osmotolerant/Falcultative halophiles
    Tolerate high osmotic pressure
  21. Besides water, what is the most important requirements for microbial growth?
    • Carbon
    • Structural backbond of organic and living matter
  22. What are the carbon sources for chemoheterotrophs and Autotrophs
    • Chemoheterotrophs- From organic materials such as protein, carbohydrates, and lipids
    • Autotrophs- From CO2
  23. Aerobes
    Microbes that use molecular oxygen to extract more energy from nutrients
  24. Anaerobes
    Microbes that do not require oxygen to extract energy from nutrients
  25. Obligate Aerobes
    • Organisms that REQUIRE O2 to live
    • At a disadvantage because O2 is poorly soluble in water
    • Bacillus anthracis

    • Microorganisms growth occur at top of test tube where oxygen is present
  26. Microaerophiles
    • Only aerobic growth
    • And only occur in low levels of [O2]
    • Nisseria gonorrhoeae

    Orgamisms will grow in middle of test tube where oyxgen is diffused to a medium
  27. Facultative Anaerobes
    • Grow best in presence of high O2
    • Can grown in aerobic OR anaerobic conditions 
    • E. coli

    Growth throughout test tube, but higher grown in higher [oxygen]
  28. Obligate Anaerobes
    • Only grow without presence of O2
    • O2 is harmful to most obligate anaerobes 
    • Clostridium spp

    Only grows in test tube where there is no oxygen
  29. Aerotolerant Anaerobes
    • Only uses anaerobic growth but can continue growth in presence of O2
    • Growth occurs evenly through entire test tube
    • Streptococcus spp
  30. Superoxide free radicals
    • O2-
    • Formed during normal respiration that use O2 as a FEA
    • Extremely dangerous because the free radicals
  31. Superoxide Dismutase (SOD)
    • Enzyme that takes free radicals and neutralizes them
    • O2- + O2- + 2H-  -->  H2O+ O2

    Or H2O2- + O2-  --> H2O2 + O2

  32. Peroxide Anion
    • O22-
    • Produced from superoxide free radicals and ALSO toxic

  33. Catalase
    • Enzymes that break down peroxide anion (O22-)
    • 2H2O--> Catalase --> 2H2O + O2

    Bubbling is O2 being released 
  34. Peroxidase
    • Enzyme that acts similar to catalase
    • H2O2 + 2H --> Peroxidase --> 2H2O
  35. Hydroxyl radical (OH)
    • Forms when H2Ois present
    • This free radical can damage any cellular component
  36. Organic Growth Factors
    • Essential organic cmpds an organism is unable to synthesize
    • Must be directly obtained from the environment 
    • Vitamins, Amino acids, Purines (A+G in nucleic acids), Pyrimidines(C+T in nucleic acids)
    • Especially necessary for fastidious organisms
  37. Purines
    A and G in nucleic acids
  38. Pyrimidines
    C and T in nucleic acids
  39. Fastidious Organisms
    Organisms that have special nutritional needs
  40. Biofilms
    • Complex intermicrobial communities in hydrogel(slime)
    • First colonists must produce capsules of slime
  41. Where are biofilms/slime/hydrogel produced?
    Lungs, mouth, throat, GI tracts, Catheters(Tubes) or Implants (heart valves, joint replacements)
  42. Patients with catheters where contaminated with
    Biofilms through heparin while using IVs
  43. What is the name of the organism that creates a biofilm that is fluorescent
    Pseudomonas Fluorescens 
  44. Biosafety Levels (BSL 1-4)
    • 1. No special precautions 
    • 2. Lab coat, gloves, eye protection
    • 3. Biosafety cabinets to prevent airborne transmission 
    • 4. Sealed, negative pressure
  45. Reproduction in prokaryotes
    • Prokaryotes have a greater surface area/vol ratio
    • Prokaryotes have a greater metabolic rate
    • Prokaryotes have greater rates of growth (once every 20 mins 60X faster than eukaryotes)
  46. 4 steps to Binary Fission
    • 1. Cell elongates and DNA is replicated 
    • 2. Cell wall and plasma membrane begin to constrict 
    • 3. Cross-wall forms, completely seperating the two DNA copies 
    • 4. Cell separates
  47. 4 phases of growth
    • Lag phase
    • Log phase
    • Stationary Phase
    • Death Phase
  48. Lag phase
    • Step 1 - Starting with inoculation
    • Bacteria adapt to new environment 
    • High metabolic activity 
    • BR less/equal to DR
  49. Log phase
    • Step 2
    • Fastest rate of cell division (exponential growth)
    • BR greater than DR
  50. Stationary phase
    • Step 3
    • Limited space and nutrients 
    • BR = DR

    Endospore form at the end of this phase
  51. Death Phase
    • 4th step
    • Waste products and age start to cause death
    • BR less then DR
Card Set
Microbial Growth
Microbial Growth