Chapter 27: Environmental Microbiology
Below you will find answers to the "Review" study questions found at the end of this chapter in Microbiology: An Introduction, 7th edition.
  1. Extremophiles include thermophiles such as Thermus aquaticus, acidophiles such as Thiobacillus, halophiles such as Halobacterium, and endoliths.
  2. The koala should have an organ housing a large population of cellulose-degrading microorganisms.
  3. Penicillium might make penicillin to reduce competition from faster-growing bacteria.


  4. 1--Any chemoheterotroph using aerobic respiration
    2--Any aerobic autotroph
    3--Any anaerobic autotroph
    4--Any chemoheterotroph producing CO2 via fermentation.
  5. Amino acids; SO42-; plants and bacteria; H2S; carbohydrates; S0.
  6. Phosphorus must be available for all organisms.
Process / Reactions / Microorganisms
Ammonification / -NH2--->NH3 / Proteolytic bacteria
Nitrification / NH3 --->NO2- / Nitrosomonas
NO2--->NO3- / Nitrobacter
Denitrification / NO3--->N2 / Bacillus
N fixation / N2---->NH3 / Rhizobium
  1. Cyanobacteria: With fungi, cyanobacteria act as the photoautotrophic partner in a lichen; they may also fix nitrogen in the lichen. With Azolla, they fix nitrogen.
    Mycorrhizae: Fungi that grow in and on the roots of higher plants; increase absorption of nutrients.
    Rhizobium: In root nodules of legumes; fix nitrogen.
    Frankia: In root nodules of alders, roses, and other plants; fix nitrogen.
  2. Settling
    Flocculation treatment
    Sand filtration (or activated charcoal filtration)
    Chlorination
The amount of treatment prior to chlorination depends on the amount of inorganic and organic matter in the water.
  1. A coliform count is used to determine the bacteriologic quality of water; that is, the presence of human pathogens or evidence of fecal contamination.
b / Leaching field
a / Removal of solids
b / Biological degradation
b / Activated sludge
c / Chemical precipitation of phosphorus
b / Trickling filter
c / Results in drinking water
  1. Activated sludge is an aerobic process that can result in complete oxidation of organic matter.
  2. Both require large areas of land and can result in the pollution of surface or groundwater if they are overloaded.
BOD / Rate of Eutrophication / Dissolved Oxygen
Untreated / 3+ / 3+ / +
Primary / 2+ / 2+ / 2+
Secondary / + / + / 3+
  1. Accumulation of BOD and loss of dissolved oxygen would be much less in a fast-moving river. Continual aeration caused by the river's movement would result in rapid oxidation of organic matter.
  2. Biodegradation of sewage, herbicides, oil, or PCBs.

Below you will find answers to the "Multiple-Choice" study questions found at the end of this chapter in Microbiology: An Introduction, 7th edition.
  1. a
  2. b
  3. b
  4. b
  5. c
  6. c
  7. b
  8. b
  9. e
  10. c
Note: The answers to the Critical Thinking and Clinical Applications questions are available to instructors only, and are found in the Instructor's Manual.