Micro- Chapter 6 Lecture

  1. describe the growth patterns of macrobes and microbes?
    • macrobe growth= increase in size
    • microbe growth= increase in cell number via binary fission (bacteria, protists, algae) or budding (yeast)
  2. why do microbes have such diverse habitats?
    • -they are small 
    • -they need small amounts of nutrients
    • -they have diverse metabolisms
    • -they can tolerate a wide variety of physical conditions
  3. what are the basic nutrients that all organisms need to survive?
    carbon, energy, and electrons/hydrogen ions
  4. what are the 4 groups of microbes, based on how they retain their carbon (nutrition) and energy.
    photoautotrophs- get energy from light and carbon from the environment

    chemoautotrophs- get energy from chemicals and energy from the environment

    photoheterotrophs- get energy from light and carbon from organic compounds

    chemoheterotrophs- get energy and carbon from organic compounds
  5. What are the 4 physical requirements for microbial growth?
    Temperature, PH, and Osmotic Pressure, and hydrostatic pressure
  6. Explain why temperature is important for microbial growth 

    what are the microbes with various temp preferences?
    • temp plays an important role because it affects the 3D structure or biological molecules. Microbes have minimum, optimum, and maximum growth temperatures. 
    • -cold causes slow growth
    • -optimal is maximum growth
    • -maximal causes denaturation to occur

    psychrophiles (cold lovers): 0-15 degrees C

    mesophiles (most pathogens): 20-40 degrees C, optimal is 37 degrees

    thermophiles (warm lovers): 45-110 degrees C
  7. Explain why PH is important for microbial growth. 

    what are the microbes with various ph preferences?
    H+ and OH- interfere with the hydrogen bonding of proteins and nucleic acids. A PH that the microbe doesn't like can destroy tertiary and quaternary protein structures and nucleic acid structures. 

    Acidophiles (acid-lovers): PH 0.1-5.4

    Neutrophiles: PH 5.4-8.0 (most human pathogens)

    Alkaliphiles (base-lovers): PH 7-11.7
  8. Why is water important in microbe growth?
    most microbes need water to dissolve enzymes and nutrients for metabolism. cells will eventually die without water although endospores and cysts can last a long time without it. 

    water also effects osmotic and hydrostatic pressure
  9. why is Osmotic pressure important for microbial growth? what are the types of osmotic pressure?
    it determines the amount of pressure put on the cell's membrane due to the dissolved substances in the solution 

    • hyperosmotic (hypertonic) environment- the substances are on the outside of the cell and cause the cell to shrink due to water loss=plasmalysis
    • *used in food preservation
    • *halophiles can live in extreme salty 

    hypoosmotic (hypotonic) environment- substances are on the inside of the cell so the cell takes up water=turgid. this is for cells with cell walls. if the cell doesn't have cell walls, then the cell bursts.
  10. why is hydrostatic pressure important for microbial growth?
    bacteria can survive to a depth of 7000m. Barophiles actually require pressure to keep their tertiary structure. 

    for each 10m of depth, water pressure increases by 1 atm pressure
  11. what are the essential elements?
    CHONPS, trace elements (Zn, Mn, Ng, etc), and vitamins/growth factors
  12. function of essential element Carbon
    Carbon acts as an energy source an is a building block for cells (carbohydrates, etc)
  13. function of essential element Nitrogen
    nitrogen is used in amino acids, purines and pyrimidines

    *nitrogen fixation- cyanobacteria and rhizobium can reduce N2 into NH3 which is an essential process to fertilize soil
  14. importance of essential element oxygen
    in aerobic microbes (obligate aerobes), oxygen is the final electron acceptor of the electron transport chain. However, superoxide radials and peroxide anions of oxygen are also toxic. these toxic forms of oxygen cause cell damage and damage to lipids and proteins
  15. name and explain the 5 types of microbes classified by their oxygen requirements.
    Aerobes- metabolize aerobically; obligate require O2

    Anaerobes- metabolize anaerobically; obligate are poisoned by O2

    Facultative anaerobes- can metabolize aerobically and anaerobically

    Aerotolerant anaerobes- metabolize anaerobically; can detoxify oxygen' poisonous forms

    Microaerophiles- require oxygen levels from 2-10%; have a limited ability to deto
  16. function of essential element Sulfur
    sulfur is for cysteine, methionine and coenzymes
  17. function of essential element phosphate
    needed for nucleic acids, ATP, and phospholipids
  18. what are the 3 types of microbe relationships? explain.
    antagonistic- one organism harms or kills the other 

    synergistic- both organisms cooperate to reap better benefits than if they were living alone (they are able to live separately) 

    symbiotic- they live in close nutritional and/or physical contact and are interdependent on each other. they do not live apart.
  19. what are biofilms?
    complex relationships between organisms. they microbes operate differently as a group than they would independently.
  20. what is quorum sensing
    bacteria respond to signals from each other and with new behaviors
  21. what are the 6 types of general culture media?
    • defined 
    • complex
    • selective
    • differential
    • anaerobic
    • transport
  22. what methods would you use to preserve a culture?
    refridgeration: 4 degrees C 

    deep freezing: -70 degrees C

    lyophilization (freeze drying)
  23. what is the mechanism that microbes grow? what is their growth pattern?
    • they grow by binary fission=the cell duplicates itself by splitting into two daughter cells. 
    • *growth is logarithmic
    • *their generation time is the time is takes the cells to double in number (20 minutes to us is 20 hours to them, for example)
    • *all cells do not divide at the same time=non-synchronous, but they do all stay in the same growth phase
  24. what are the phases of microbial growth? explain.
    lag phase

    log phase- growth at exponential rate (meaning, 2, 4, 8, 18, etc). this phase has a finite number because as bacterial increase in number, nutrients and depleted and waste accumulates. the limiting factor is the rate of energy production from ATP 

    stationary phase- this is the leveling out phase. nutrition is limited, wastes may be at toxic levels, there isn't enough O2 and PH isn't at its optimal level. 

    death/decline phase- too much waste, and not enough nutrition, cells begin to die.
  25. what are the 5 direct methods of counting microbial growth?
    Viable plate counts

    Membrane filtration

    Microscopic counts

    Electronic counters

    Most probable number
  26. what are the indirect methods of measuring microbial growth?
    • turbidity- measuring with a spectrophotometer
    •  (the metabolic products or the dry weight)
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Micro- Chapter 6 Lecture