Micro Ch 6

Home > Preview

The flashcards below were created by user skoops on FreezingBlue Flashcards.

  1. What are the 4 phases of microbial growth ?
    Image Upload

    • Lag: no growth ( adjusting) 
    • Log: Rapid growth 
    • Stationary: Slowed growth due to high cell density
    • Death: pop goes down ( no food left)
  2. Which microbial growth phase is characterized by rapid growth of the organism?
  3. Which microbial growth phase is characterized by a slowing or stopping of growth due to high cell density being present?
  4. Which microbial growth phase occurs when a small number of the microbes have been placed into a new environment
    • Lag  = no growth
    • ( the microbes are adjusting to the new environment)
  5. What are the physical requirements required for growth?
    • Temperature
    • pH
    • Osmotic Pressure
  6. Temperature growth for Psychrophiles
    Cold loving 

    • 0C - 20 C 
    • cause food spoilage
  7. Temperature growth range for Psychotrophs
    • 0-30 C 
    • cause food spoilage
  8. Temperature growth for Mesophiles
    • Moderate temp(around the human range) 
    • 10-50C
  9. Temperature growth range for Thermophiles
    • Heat loving 
    • 40-70C
  10. Why is osmotic pressure important for microbial growth?
    Osmotic pressure increases: Microbial growth decreases 

    • Microbes get most nutrients from water to grow 
    • Hypertonic environments ( salt, sugar)=plasmolysis 
    • - The cell water leaves the cell , and the cytoplasm shrinks 

    - bacteria can't grow ex. used to preserve food ( honey, salted fish. The plasma membrane pulls away from the cell wall
  11. pH range ideal for most bacteria?

    What range is lethal for most bacteria
    • 6.5-7.5 = best 
    • 1-4, 10-12 = lethal
  12. Chemical requirements for growth
    • Carbon 
    • Nitrogen, sulfer, phosphorus
    • Oxygen
    • Organic growth factor
    • Trace elements
  13. 2 Uses of Carbon for microbial growth
    Energy ( make vitamins, purines..etc) 

    Chemoheterotrophs ( humans) = get C from organic materials 

    Autotrophs  get C from CO2
  14. 2 Uses of Nitrogen in microbial growth
    Used to make amino acids and proteins to decompose protein 

    Use for NH4 or NO3
  15. 2 Uses for Sulfer in microbial growth
    • Used to make sulfur-containing amino acids, and vitamins ex. Thiamine, and biotin 
    • - Most bacteria decompose protein 
    • Some use SO4, or H2S
  16. 2 uses for Phosphorus for microbial growth
    • To make DNA, RNA and membranes 
    • PO4
  17. Effect of O2 on growth in Obligate Aerobes
    Require O2 

    In test tube : growth is close to the top
  18. Effect O2 has on Facultative Anaerobes
    • Can use 02 but can grow if its not available
    • Test tube: most growth is on the top, but its spread out on the bottom
  19. Effect of 02 on Obligate Anaerobes
    Grow only without 02 

    Test tube: growth only on the bottom
  20. Effect of 02 on Aerotolerant anaerobes
    Grows evenly , no O2
  21. Effect of 02 on Microaerophiles
    Need low 02 

    growth only in the middle
  22. How to determine if a microbe is a strict anaerobe?
    Growth is only on the bottom, no 02
  23. 4 Forms of Toxic Oxygen
    • 1) Singlet Oxygen : 02 boosted to a higher state ( due to light absorption) 
    • = minor damage 
    • 2) Superoxide free radicals : Made by the immune system to kill microbes , by stealing negative charges 
    • = extremely damaging 
    • 3) Peroxide Anion . Ex. hydrogen/benzoyl peroxide 
    • = extremely toxic 

    • -- to protect from damage: uses catalase to turn it into water 
    • 4) Hydroxyl radical: Made by immune system, very reactive 
    • -- antioxidants as protection
  24. Advantages of forming biofilms
    • Microbial communities 
    • Form slime/hydrogens ( bacteria are attracted by chemicals via quorum sensing) -- communicate 
    • -share nutrients 
    • -sheltered from harmful factors ( desiccation, antibiotics, and the body's immune system) 
    • -transfer genetic info
  25. Define culture medium
    nutrients prepared for microbial growth
  26. Define sterile
    No living microbes
  27. Define Inoculum
    Put microbes into a medium
  28. Define culture
    Microbes growing on/on a culture medium
  29. What is agar? Why is it useful for growing microbes?
    Complex polysaccharide, used as a solidifying agent for culture media in petri plates, slants, and deeps 

    • Not metabolized by microbes
    • It liquefies at the boiling point of water
  30. Chemically defined vs complex media
    chemically defined : exact chemical composition is known

    complex media: chemical comp varies from batch to batch
  31. What is reducing media used for ? What types of organisms would grow in these conditions?
    Ex. level 4 bio labs 

    • Media with chemicals ( thioglycolate / oxyrase) that combines O2 
    • Heated so there is no O2 

    - Anaerobes grow because there is no Oxygen
  32. What are capnophiles
    • Microbes that require high CO2 conditions 
    • ( candle in a jar, with co2 packet)
  33. What is selective media?
    Suppress unwanted microbes and encourage desired microbes
  34. What is Differential Media?
    Make it easy to distinguish colonies of different microbes
  35. Can selective and differential media be used at the same time?
  36. How to make an enrichment culture for a particular organism
    • Encourage growth of a desired microbe
    • Ex. soil sample, isolate microbe so that it can grow on phenol
    • 1) soil + liquid enriched medium with phenol as only energy
    • 2) Incubate, then transfer culture, transfer again, incubate
    • 3) Only phenol- metabolized bacteria will grow
  37. Define colony , and why does a colony not grow to an infinite size, or at least fill the confines of the Petri plate ?
    A population of cells from 1 cell/spore/group of attachement 

    Doesnt grow infinite amount because of nutrient exhaustion
  38. Describe how pure cultures can be isolated by using the streak plate method
    • A loop is dipped into the culture, and streaked 
    • Cells rub off = isolated colonies
  39. Define bacterial growth
    Increase in the number of cells, not the size of the cell
  40. Define binary fission
    bacteria reproductive method 

    1 cell splits in 2
  41. How to calculate how many cells are present after 15-20 generations
    • Ex. 5 generations = 2to the 5th power= 32 cells
    • Ex. 10 generations = 2 to the 10th power= 1024 cells
  42. Be able to calculate # of generations
    # generations = log ( end cells) - log ( cell start) / log(2)
  43. Calculate generation time
    generation time = 60 min x # hours/ # of generations
  44. Why bacterial growth is plotted as a logarithmic plot instead of  a linear plot
    a linear plot does not clearly show the population changes in the early stages of the growth curve ( first 10 generations dont even appear)
  45. Describe the serial dilution process
    Image Uploadits done to more easily calculate colonies formed
  46. Direct measures of cell growth
    • - Plate count ( after incubation count colonies on the plate) 
    • - Direct microscopic count ( membrane filtration) 
    • -Serial Dilutions
  47. Indirect measures of growth
    (metabolic activity is measured ) 

    • -Turbidity: cell growth cloudiness ( measure light passing through) 
    • -Metabolic activity 
    • - Dry weight ( remove extraneous material ,and weighed)

Card Set Information

Micro Ch 6
2016-09-17 21:46:09
Microbial Growth
Show Answers:

Home > Flashcards > Print Preview