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SECTION 2.4 QUESTIONS
(Page 112)
Understanding Concepts
1. Most organisms in kingdom Archaebacteria thrive under extreme conditions that other organisms could not
tolerate.
Most live without oxygen. The thermophiles obtain energy by oxidizing sulfur and function in extremely hot
environments.
The methanogens live in volcanic sea vents and metabolize carbon dioxide to produce methane. The halophiles
live in extremely salty environments and use sunlight for energy.
2. Archaebacteria contribute to human society in the following ways: digestion of sewage and oil spills; alternate
fuel
source; cancer research; production of bioplastics; production of enzymes for food processing, perfume
manufacture;
pharmaceuticals; and enzymes used in molecular biology.
3. Classification of eubacteria according to shape, respiration, and nutrition:
44 U nit 2 Student Book Solutions NEL
NEL Section 2.4 45
4. Anaerobic bacteria live in the absence of oxygen. They thrive in any area without air circulation: in the soil,
inside the
body, or inside a sealed container (e.g., home canning).
5. Conjugation is considered a form of sexual reproduction in bacteria because genetic material is exchanged
through the
pilus. The new organisms are genetically different from their parents.
6. During unfavourable conditions (e.g., drought, removal of food source), bacteria go into dormancy by forming
resting
cells called endospores. Genetic material is encased by a thick, resistant cell wall. When conditions improve, this
wall
dissolves and bacterial function resumes.
7. (a) streptococcus (b) bacillus (c) coccus
8. Identification of E. coli:
Anatomy Physiology
– thrives in both aerobic and anaerobic conditions
– heterotrophic
– feeds on substances in the human intestine, digesting
food and synthesizing vitamin K and B-complex vitamins
Making Connections
9. Summary of Gram stain technique:
(a) Flood slide with crystal (or gentian) violet for 10 s. (Wash with running tap water.)
(b) Flood with Gram’s iodine for 10 s. (Wash with water.)
(c) Carefully decolourize with 95% ethanol until thinnest parts of the smear are colourless. (Wash with water.)
(d) Flood with safranin (pink colour) for 10 s. (Wash with water.) Air-dry or blot with absorbent paper.
Organisms that retain the violet-iodine complexes after washing in ethanol stain purple are termed Gram-positive;
those
that lose this complex and stain red from the safranin counterstain are termed Gram-negative. Examples of Gramnegative
bacteria are Escherichia coli, Salmonella typhi, Vibrio cholerae, and Bordetella pertussis. Examples of Grampositive
bacteria are Staphylococcus epidermidis, Streptococcus pyogenes, Actinomyces odontolyticus, and Clostridium
tetani.