Microbiology - Microbial Growth and Nutrition (Ch. 6)

  1. What are the four toxic forms of oxygen?
    • 1) Singlet Oxygen (1O2)
    • 2) Peroxide Anion (O2-)
    • 3) Superoxide Radical (O22-)
    • 4) Hydroxyl Radical (OH-)

    (6, 167-168)
  2. What is a chemotroph?
    Organisms that acquire energy from redox reactions involving organic and inorganic chemicals.

    (6, 166)
  3. What are the six types of general culture media?
    • 1) Defined Media
    • 2) Complex Media
    • 3) Selective Media
    • 4) Differential Media
    • 5) Anaerobic Media
    • 6) Transport Media

    (6, 178)
  4. What is another name for heterotroph?

    (6, 166)
  5. How do most unicellular microorganisms reproduce?
    Binary fission, where the cell doubles in size and divides in half to produce two identical daughter cells.

    (6, 182)
  6. Explain complex media.
    Complex media is a growth medium in which the exact composition is unknown. They contain nutrients released by the partial digestion of yeast, beef, soy, or protein.

    (6, 178)
  7. Explain selective media.
    Selective media is a growth medium the either favors the growth of a particular microorganism or inhibit the growth of unwanted ones.

    (6, 178)
  8. Explain differential media.
    Differential media is a growth media formulated such that either the presence of visible changes in the medium or differences in the appearance of colonies can be used to differentiate among different kinds of bacteria growing on the medium.

    (6, 179)
  9. What is an enrichment culture?
    A growth culture that makes use of a selective medium and is designed to increase very small numbers of a chosen microbes to observable levels.

    (6, 181-182)
  10. What is generation time?
    Generation time is the time required for a bacterial cell to grow and divide.

    • *Another way to look at it...
    • The time required for a population of cells to double in number.

    (6, 183)
  11. What is serial dilution?
    Serial dilution is the stepwise dilution of a liquid sample.

    (6, 185)
  12. What are barophiles?
    Organisms that live under extreme pressure, such as the bottom of the ocean.

    (6, 173)
  13. What is a heterotroph?
    Organisms that catabolize organic molecules (proteins, carbs, amino acids, and fatty acids) they acquire from other organisms.

    (6, 166)
  14. What is an autotroph?
    Organisms that utilize an inorganic source of carbon (CO2) and make organic compounds from it. Thus, they don't need to acquire carbon and organic compounds from other organisms.

    (6, 166)
  15. What is a phototroph?
    Organisms that use light as their energy source.

    (6, 166)
  16. What is a colony forming unit (CFU)?
    The progenitor from which a particular pure culture is derived.

    (6, 176)
  17. What are the three categories of microorganisms based on their tolerance of pH levels?
    • 1) Neutrophiles (pH between 6.5-7.5)
    • 2) Acidophiles
    • 3) Alkalinophiles

    (6, 171)
  18. What is crenation?
    • Crenation is the shriveling of a cell when placed in a hypertonic solution, resulting in shrinkage and the acquirement of a notched or scalloped surface.
    • *Cells can die from this.

    (6, 172)
  19. What is osmotic pressure?
    Osmotic pressure is the pressure exerted on a semipermeable membrane by a solution containing solutes that cannot freely cross the membrane.

    (6, 172)
  20. What are obligate halophiles?
    Obligate halophiles are microbes which are adapted to exist under high osmotic pressure, such as salt ponds.

    (6, 172)
  21. What is lyophilization?
    Lyophilization is a preservation technique where a culture is instantly frozen in liquid nitrogen or liquid CO2 then the frozen water is removed from a culture using an intense vacuum in such a way that there is no permanent damage to cellular structures and chemicals. These cultures can be preserved for decades before being revived. 

    (6, 182)
  22. Deep-freezing preservation technique happens at what temperature range?
    -50o to -90o Celsius

    (6, 182)
  23. Explain defined media.
    • A medium in which the exact composition is known.
    • *Also known as a synthetic medium.

    (6, 178)
  24. Describe the general chemical makeup of the dry-weight of cells.
    • Carbon, hydrogen, oxygen, and nitrogen make up 95% of the dry-weight of a cell.
    • The rest is composed of  phosphorus, sulfur, calcium, manganese, magnesium, copper, iron, and a few other elements.

    (6, 169)
  25. What is nitrogen fixation and why is it important?
    Nitrogen fixation is a process where certain bacteria (many cyanobacteria) reduce nitrogen gas (N2) to ammonia (NH3). Without this process, nitrogen would not be available in a useable form for other organisms, because they can't utilize nitrogen its nitrogen gas (N2) form.

    (6, 169)
  26. What are growth factors?
    Growth factors are certain necessary organic chemicals that organisms need for growth but that they cannot synthesize themselves.

    *Vitamins are an example.

    (6, 169)
  27. What is quorum sensing?
    How does it work?
    Quorum sensing is a system of stimulus and response correlated to population density.

    As the density of microorganisms increases, the concentration of signal molecules the cells emit increases, and the more receptors bind to these molecules. Then, when the concentration exceeds a certain threshold, the expression of previously suppressed genes is triggered, leading to the creation of biofilms and other new characteristics (production of enzymes, changes in cell shape, formation of mating types, and more).

    (6, 173)
  28. What does the word axenic refer to?
    Axenic refers to a pure culture.

    (6, 176)
  29. What is a clinical specimen?
    A clinical specimen is a sample of human material (saliva, blood, feces, etc.) that is examined or tested for the presence of microorganisms.

    (6, 175)
  30. What are microaerophiles?
    They are organisms that require oxygen levels of 2-10%, presumably because they have a limited ability to detoxify hydrogen peroxide and superoxide radicals.

    (6, 168)
  31. What are the three things all cells need for metabolism?
    • 1) A source of energy
    • 2) A source of electrons or hydrogen atoms
    • 3) A carbon source

    (6, 166)
  32. What is another name for autotroph?

    (6, 166)
  33. Compare antagonistic, synergistic, and symbiotic relationships.
    • Antagonistic - relationship in which one organism harms or even kills another organism.
    • Synergistic - relationship in which individuals cooperate and benefit from each other, but do not need each other to survive.
    • Symbiotic - relationship where organisms live in such close nutritional or physical contact such that they rarely (if ever) live outside the relationship.

    (6, 173)
  34. What are the effects of gaseous oxygen (gO2) on aerobes compared to anaerobes?
    Aerobes need gaseous oxygen to survive, anaerobes are harmed (if not killed) by it.

    (6, lecture)
  35. What are three special culture techniques?
    • 1) Animal and cell cultures
    • 2) Low-oxygen cultures
    • 3) Enrichment cultures

    (6, 181-182)
  36. What is an inoculum?
    An inoculum is a sample of microorganisms.

    (6, 174)
  37. Why are organisms sensitive to changed in acidity (pH levels)?
    They are sensitive to changes in acidity because hydrogen ions and hydroxyl ions interfere with hydrogen bonding within proteins and nucleic acids.

    (6, 171)
  38. What is agar?
    Agar is a complex polysaccharide derived from the cell walls of certain red algae. It serves a gelling agent within a variety of growth media.

    (6, 176-177)
  39. List the four temperature categories for microbes and the approximate temperature ranges in which they can survive.
    • 1) Psychrophiles: -5 - 20oC
    • 2) Mesophiles: 15 - 45oC
    • 3) Thermophiles: 43 - 80oC
    • 4) Hyperthermophiles: 68 - 105oC

    (6, 170-171)
  40. What are aertolerant anaerobes?
    They are organisms that do not use aerobic metabolism, but they tolerate oxygen by having some of the enzymes that detoxify oxygen's poisonous forms.

    (6, 168)
  41. What are facultative anaerobes?
    The are anaerobic organisms that can maintain life via fermentation or anaerobic respiration, though their metabolic efficiency is typically reduced in the absence of oxygen.

    (6, 168)
Card Set
Microbiology - Microbial Growth and Nutrition (Ch. 6)
Microbiology - Microbial Growth and Nutrition (Ch. 6)