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slice and examining it under an oil immersion lens. Viral identification requires an electron microscope.
(o) Commercial dryers would be available in a college-level food technology program. This equipment controls both
temperature and humidity, both of which can be varied to provide optimum conditions. A sulfuring cabinet may be
used to preserve food colour during the drying process. Solar dryers are being developed, but it is more common to
mechanical dryers
in use in college food technology programs. Silo dryers have trays or tanks to accommodate a
Unit find
2 Microbiology
Review
deeper layer of food than cabinet dryers.
UNIT 2
REVIEW
(Pages 154–157)
Understanding Concepts
1. (a) Many answers are possible. The characteristics of protists, fungi, and bacteria do not fit into the groups of plants
or animals. For example, fungi have cell walls like plants but do not contain chlorophyll. Some protists move in
ways similar to animals, but many of these organisms also contain chloroplasts.
(b) Bacteria were not seen by Aristotle. Some organisms may have chlorophyll and cell walls similar to plants, but
they also lack a nuclear membrane. Other bacteria have flagella—a characteristic of animals and protists; they also
lack chlorophyll. Plant cells and animal cells have a different appearance when viewed under a microscope. If
Aristotle had been aware of this, he may have developed a different classification scheme. Both plant and animal
cells have a true nucleus. Plant cells have cell walls and chlorophyll, while animal cells have no cell walls or
chlorophyll. Some bacteria and protists would have been difficult for Aristotle to classify as plants or animals.
Bacteria have no true nuclei, but contain cell walls; some bacteria contain chlorophyll. Euglena has chloroplasts,
but no cell wall. Euglena also has a true nucleus. Fungi have cell walls and nuclei but no chlorophyll.
2. (a) Escherichia coli—Eubacteria
(b) Plasmodium—Protista
(c) Giardia lamblia—Protista
(d) adenovirus—other
(e) methanogens—Archaebacteria
(f) Bacillus anthracis—Eubacteria
(g) lichen—Protista
(h) yeast—Fungi
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3. In support of the claim that viruses are nonliving, one might argue that viruses are not cells: they have no nucleus,
cytoplasm, or cellular organelles. Viruses have no cellular respiration, so they do not exchange gases, and they do not
feed or reproduce (outside a host cell). To refute the claim that viruses are nonliving, one might argue that viruses
contain genetic material, are capable of reproduction (when inside a host cell), and exhibit genetic variation over time.
4. The invading virus takes over control of the host cell and directs it to expend energy making viral particles. Normal
functioning of the host cell, including protein synthesis, stops.
5. Eubacteria contain peptidoglycan in their cell walls; Archaebacteria lack this component. Most Eubacteria metabolize
with oxygen; most Archaebacteria live without oxygen and thrive in extreme environments (hot, salty, sulfurous).
6. Products that rely on a bacterium for part of their production include: alternate fuel sources; acetone; bioplastics;
stonewashed jeans; enzymes used in food processing (dairy products, vinegar); perfume manufacture; antibiotics and
other pharmaceuticals.
7. Comparison chart of viruses, bacteria, protists and fungi:
Feature
Viruses
Bacteria
Protists
Fungi
cell structure
not a cell
prokaryotic
eukaryotic
eukaryotic
genetic material
DNA or RNA
DNA loop or plasmid
nucleus containing
chromosomes
nucleus containing
chromosomes
locomotion
carried in air or
moisture
flagella
cilia; flagella;
pseudopods
nonmotile
reproduction
replication via
lytic and
lysogenic cycles
binary fission;
conjugation;
form endospores
binary fission;
conjugation;
spore formation
asexual and sexual
life cycles; spore
formation
nutrition
supplied by host
most are heterotrophs;
some autotrophs
most are heterotrophs;
some autotrophs
heterotrophs
habitat
host cell
nature or host cell
aquatic or moist
environments
terrestrial
niche
parasite
producer, consumer,
saprophyte, or parasite
producer, consumer,
or parasite
consumer
8. In Figure 1 (p. 154 of the Student Text), an amoeba is feeding. Students should draw two previous sketches in the
sequence (amoeba with pseudopod approaching food; pseudopod engulfing food particle and drawing it into the
organism). An after-sketch would show the lysis of food vacuoles after digestion is complete.
9. Bacteria are involved at every level of the food chain. Some bacteria are photosynthetic and take energy directly from
the sun to produce oxygen and food. At the consumer and producer levels, bacteria act as saprophytes, releasing digestive enzymes into dead organisms and causing organic material to decay. Without decay, dead organisms would accumulate and nutrient cycles would cease to function. Bacteria play an important role in the nitrogen cycle, “fixing” this
nutrient into a usable form for producers. Arrows can also be drawn from bacteria to the deer and fox, because these
organisms take up bacteria and rely on their enzymes to digest nutrients.
sun
trees
bacteria
bacteria
deer
fox
bacteria
bacteria
10. Comparison of cilia and flagella:
Cilia
Similarities
By beating, can produce cell movement
Differences
– tiny (<10 µm), hairlike, protein structures
present on the surface of many cells, notably
protists and some types of vertebrate epithelium
– usually occur in large groups
– beating can create a current in fluid surrounding
the cell
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Flagella
– relatively long (up to 150 mm), fine,
whiplike structures present on the
surface of some cells, e.g.,
spermatozoa, protists
– occur singly or in small groups
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11. Figure 3 (p. 154 of the Student Text) shows conjugation, a sexual form of reproduction. Genetic information is
exchanged; new organisms are genetically different from their parents. In binary fission, the usual form of reproduction in protists, one mother cell produces two genetically identical daughter cells.
12. Algae supply about 80% of the world’s oxygen. Algae are consumed as food; used in the production of fertilizers,
consumer products and pharmaceuticals; and are instrumental in creating petroleum resources. Phytoplankton and
zooplankton occupy essential levels in aquatic food chains.
13. Answers will vary. Students may argue that most protists are unicellular eukaryotes, so do not belong in any of the
other kingdoms. However, there are many exceptions: algae are multicellular but do not form tissues; fungilike protists
form colonies of identical cells. Attempts to classify protists according to the following characteristics show the vast
diversity of this kingdom: size (2 µm length to 5 cm diameter); shape (amorphous—Amoeba; slipper—Euglena and
Paramecium; filamentous—algae; plasmodium—slime moulds); structure (simple—Amoeba—to complex—
Paramecium); locomotion (flagella, cilia, pseudopods, free floating, parasitic); respiration and nutrition (some
autotrophs—algae, Euglena; most are heterotrophs); habitat (fresh or salt water, animal fluids, or very damp terrestrial
environments); and role (some essential to life on Earth, others are pathogenic).
14. Plantlike features of fungi include: eukaryotic; many cell organelles; cell walls; most are anchored in soil or other
substrate; nonmotile; reproduction can be asexual, sexual, or both.
15. The vegetative body or mycelium of a fungus may be present but unnoticed because it exists below soil level.
16. There are over 700 known yeast species and almost as many ways of using this organism. Yeasts are used nutritionally (as a dietary supplement), agriculturally (in a process called effective microorganisms technology), industrially (in
the production of ethanol), and medically (in gene therapy).
17. Antibiotics are administered after pathogenic bacteria have entered the body and triggered an immune system
response. They work by preventing bacteria from manufacturing proteins or constructing a normal cell wall. In each
case, normal cell processes are disrupted and bacteria that are causing the infection die. Vaccines work by stimulating
the immune system with a structure so similar to a specific pathogen that antibodies are produced. When the “real”
pathogen enters the body, memory cells quickly trigger antibody production, and the antigen is neutralized before an
infection takes hold.
18. diphtheria (3); whooping cough (4); oral polio (1); measles (1); mumps (1); smallpox (5); tetanus (3); injected polio (2)
19. Figure 5 (p. 155 of the Student Text), Old Man’s Beard, is a lichen—a symbiotic partnership of an algae and a sac
fungus. The fungal mycelium surrounds the algal cells and provides them with essential minerals, carbon dioxide, and
water for photosynthesis. The mycelium also lends structural support to the entire organism. The algae share the carbohydrates they manufacture from carbon dioxide with the fungi. Lichens are an important source of food for caribou and
other animals in the arctic tundra and boreal forests of northern Canada. Lichens are involved in plant succession: by
being able to establish themselves on rocks and in barren areas, lichen help form basic soil material. Concentrations of
pollutants in an area can be assessed by monitoring the presence or absence of different lichens because lichens absorb
water directly from the air.
20. smallpox (N); measles (N); anthrax (Y); E. coli food poisoning (Y); Streptococcus throat infection (Y); rabies (N);
malaria (Y); viral throat infection (N)
21. Biotechnology is the use of living things in industrial or manufacturing applications. Traditional methods of biotechnology include the production of penicillin from moulds and the use of bacterial enzymes to make cheese and yogourt.
Recombinant DNA technology and viral vectoring are two new biotechnology methods that involve gene manipulation.
22. (a) The application of chemicals (pesticides: fungicides, herbicides, insecticides) kills microorganisms in the soil and
decreases the natural coating of microorganisms on leaf surfaces.
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(b) Soil can be enriched in a more balanced way through effective microorganisms (EM) applications and the use of
integrated pest management (IPM). EM is a cocktail of microorganisms blended in a sugar medium at low pH.
EM application improves soil structure, increases fertility, and reduces disease and the need for pesticides. IPM
uses a combination of cultural, biological, genetic, and chemical methods to control pests in parks and open areas.
Decisions are made that present the lowest health risk to humans, have a minimum impact on nontarget organisms, have greatest effect on target species, and present the least risk to the environment and biodiversity.
23. There is a zone of antibiotic release around the mycelium of the soil fungus. In this area, no other microorganisms
grow. This zone gives the soil fungus a competitive advantage for space, water, and food; otherwise, there would be
competition for these resources.
24. Concept map:
binomial
nomenclature
Linnaeus
Staphylococcus
Eubacteria
mushrooms
Protista
extreme
halophiles
Paramecium
taxonomy
E. coli
Amoeba
Archaebacteria
green algae
Fungi
kingdoms
bread
mould
methanogens
25. HIV is an example of a retrovirus. Lysogeny is an important part of the life cycle of this RNA virus. During the lysogenic cycle, the virus invades and integrates with host DNA, lying dormant for many years before resuming replication
in the lytic cycle. Many other viruses (e.g., smallpox, mumps, influenza) do not go through the process of lysogeny.
Replication occurs quickly in the lytic cycle, and symptoms appear in the host shortly after exposure to the virus.
Applying Inquiry Skills
26. Answers will vary. A possible dichotomous key to classify the viruses:
1.
2.
3.
4.
5.
6.
7.
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a.
b.
a.
b.
a.
b.
a.
b.
a.
b.
a.
b.
a.
b.
geometric shape
head-and-tail shape
cylindrical form
non-cylindrical form
evenly spaced bumps on surface
spiral protrusion visible
a bulging square
spherical
flat face
rounded face
flattened oval
spherical
nail-like protrusions
rounded protrusions
go to 2
bacteriophage
go to 3
go to 4
Ebola virus
tobacco mosaic virus
smallpox virus
go to 5
adenovirus
go to 6
pox virus
go to 7
HIV
rhinovirus
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27. (a) From the information given in this unit, protist A is Euglena, protist B is Paramecium, and protist C is Amoeba.
There are other possibilities within the kingdom Protista.
(b) Protist A is likely a producer. Protists B and C are consumers. They may also be parasites.
28. (a)
Bread Mould Growth
Number of Colonies
60
50
40
30
20
10
0
2
4
6
8
Time (day)
pH 4.0
pH 5.5
pH 7.0
(b)
(c)
(d)
(e)
A pH of 5.5 appears to be optimal for bread mould growth.
Controlled variables include: moisture level, light level, type of bread used, container, location, and handling.
Growth at all pH levels suggests that bread is a suitable substrate for Rhizopus.
Acidity appears to promote mould growth, so a neutral or basic pH might retard mould growth. Other environmental conditions to prevent mould growth are: light, cold, low moisture, absence of food source.
29. (a) Lactic bacteria, yeasts, moulds, and proteolytic bacteria are four microorganisms that grow in raw milk.
(b) Proteolytic bacteria: organisms that break protein down into simpler soluble substances using a hydrolytic
process.
(c) A–B is the exponential phase: lactic acid bacteria are multiplying by converting the milk sugar lactose into lactic
acid. B–C is the stationary phase: lactic bacteria have run out of nutrients, or they have produced wastes that limit
their growth. A flat curve indicates that the death rate is equal to the growth rate. However, the drop in pH has
provided favourable conditions for yeasts and moulds. C–D is the death phase: proteolytic bacteria are digesting
the remains of other organisms, and eventually, themselves.
(d) Growth of lactic acid species peaks at 1.5 days. Growth should be halted just before this stage if a milk product
is produced from this species.
(e) Optimum pH for mould growth appears to be 4.4.
(f) There is an inverse relationship between pH and time in milk spoilage: as time increases, pH decreases.
30. IPM uses a combination of cultural, biological, genetic, and chemical methods to control pests in parks and open areas.
Decisions are made that present the lowest health risk to humans, have a minimum impact on nontarget organisms,
have greatest effect on target species, and that present the least risk to the environment and biodiversity. Pest populations may not be eradicated using this method, but they are kept under control. With this balanced approach, there is
a less dramatic effect on the diversity of soil organisms than there would be with widespread use of chemicals.
Making Connections
31. Helpful and harmful roles of E. coli:
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Helpful role of E. coli bacteria
Harmful role of E. coli bacteria
– live in the human intestine; involved in food
digestion and synthesis of vitamins K and B
– used in recombinant DNA process to produce
useful proteins and enzymes such as insulin,
GH, and EPO
– present in water through fecal contamination;
detected by coliform test
– one strain (E. coli O157:H7) is responsible
for systemic poisoning and could lead to death
– another strain is present in raw meat and causes
hemolytic uremic syndrome (HUS), more commonly
known as “hamburger disease”
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32. Antibiotics are effective only against bacteria. Some throat infections are caused by viruses. If test results indicate that
the infectious organism is bacterial, the doctor may prescribe an antibiotic. If viral, the doctor will likely advise rest
and fluids. Inappropriate dispensing of antibiotics is contributing to antibiotic resistance.
33. There are many different kinds of leukemia—cancer of the blood, bone marrow, and liver—but most are characterized
by an abnormally high rate of white cell production. Although many more white blood cells are produced, these are
abnormal cells that cannot help the body fight infections. White blood cell function is essential to immune system
response. Lymphocytes— plasma and memory cells—make antibodies when stimulated by antigens. Without adequate
lymphocyte function, a cancer patient’s system cannot respond to an infectious agent, and is susceptible to many lowgrade pathogens that would otherwise be neutralized. For this reason, people with leukemia often get infections and
have fevers. A person with leukemia would need to reduce exposure to pathogens, and maintain high standards of
personal cleanliness.
34. Answers may vary. A sample answer in support of vaccination is provided. Polio remains a debilitating disease.
Although it is uncommon, it is not totally eradicated. It replicates quickly and is a highly contagious virus. Simple
precautions, including vaccination, protect children from random exposure and a lifetime of side effects.
35. Dysentery is an inflammation of the intestine that results in the frequent passage of feces, usually with blood and
mucus. The two most common causes of dysentery are infection with a Shigella bacillus, and infestation by an amoeba,
Entamoeba histolytica. Both types are spread by fecal contamination of food and water and are most common where
sanitation is poor. They are primarily diseases of the tropics but may occur in any climate. Canada has a secure water
supply that is generally well monitored and tested. In cases of contamination, the population is warned to boil local
water or obtain water from other sources. Advice is generally followed, so it is rare to see cases of dysentery associated with water contamination. However, our food is imported from many countries around the world, and residues of
bacillus and amoeba remain on the surfaces of fruits and vegetables. Incomplete washing could result in dysentery.
Other cases are brought home from travellers abroad.
36. The following responsible steps can be taken to reduce the problem of eutrophication: limit your fertilizer use and
apply at appropriate times; use environmentally-friendly landscaping instead of grass; control run-off and soil erosion;
start a compost pile and recycle yard waste; conserve water and energy; plant trees; maintain your septic system; drive
less; be a responsible boater and pump out wastes; get involved.
37. Facts about livestock infectious diseases from the Nelson Science Web site links:
• Foot-and-mouth disease affects cattle, sheep, pigs, and goats. The disease is caused by a viral infection and is spread
through airborne particles, infected meat, dung, animals, humans, and other physical objects that have come into
contact with the virus.
• Mad-cow disease, or bovine spongiform encephalopathy (BSE), is thought to be caused by a type of prion. Prions
are subviral proteins that are linked to eight rare, fatal, degenerative diseases of the nervous system. The transmission of BSE is still the subject of much debate, but it’s thought to be related to the use of feed prepared from the
carcasses of infected cattle.
38. Fungi are responsible for recycling usable nutrients back into the soil by the decomposition of organic matter. This makes
nutrients available for plants to absorb through their roots. Some fungi form symbiotic relationships with plants: in
mycorrhizae, an extensive network of hyphae helps the roots of plants absorb specific nutrients. In addition, fungal
mycelia break up the soil, freeing space for the movement of gases, water, and beneficial soil organisms like earthworms.
39. There are short-term benefits to pesticide use: prevention of crop diseases (potato blight), increased land productivity,
and eradication of insect vectors of human disease (malaria, West Nile virus). However, prolonged use reduces biodiversity. Natural organisms in the soil are killed, affecting nutrient cycles, plant growth, and the local food chain.
40. Moving genes from one organism to another provides new gene combinations beyond those possible by sexual reproduction. Current genetic research is focused on correcting genetic defects (ADA deficiency, CF). As genomes are
mapped, the possibility exists of designing and creating new organisms and significantly altering existing ones. As
students consider the implications of “dialing up” children with green eyes or Einstein’s intelligence, answers will
vary. Gene therapy is expensive and may be available to only a select few. Its use is unlegislated and unregulated at
present and its long-term safety is unknown. This issue is widely debated by religious, cultural, and scientific communities, and student opinions may reflect this controversy.
41. Summary of human growth hormone information from the Nelson Science Web site:
• GH (also called somatotropin) is a protein of 191 amino acids. It is secreted by the pituitary gland upon stimulation from the hypothalamus.
• GH promotes body growth by binding to receptors on the surface of liver cells and stimulating them to release
insulin-like growth factor-1 that acts directly on the ends of the long bones to promote their growth.
• Pituitary abnormalities in childhood: hyposecretion of GH produces the stunted growth of a dwarf while hypersecretion leads to gigantism. Pituitary abnormalities in adults: a hypersecretion of GH leads to acromegaly.
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• GH from domestic mammals like cows and pigs does not work in humans. Use of GH from the glands of human
cadavers was halted when several patients died from a rare neurological disease attributed to contaminated glands.
Gene therapy uses E. coli bacteria to synthesize recombinant human GH.
• The main use of GH is to correct the deficiency, but many other claims have been made about its effect: younger,
thicker skin; stronger bones; an average gain of 8.8% in muscle mass after six months without exercise; an average
loss of 14.4% body fat after six months without dieting; a stronger immune system; better exercise performance; a
higher energy level; greater cardiac output; lower cholesterol; regrowth of heart, liver, spleen, kidneys, and other
organs that shrink with age; tissue regeneration in the healing of wounds and recovery from surgery; improved
kidney function; lower blood pressure; fewer wrinkles; elimination of cellulite; sharper vision; and better retentive
memory.
42. (a) This example represents mutualism.
Benefits to algae include: protection, carbon dioxide, and a tight cycling of nitrogenous wastes. Benefits to coral
include: organic carbon (glycerol, sugars, and amino acids) and an increased rate of skeletal growth in such a way
that it maximizes the sunlight for algal photosynthesis.
(b) If much of the coral’s needs are met by the accompanying algae, it can survive in nutrient-poor water without the
competition from other species that would exist in nutrient-rich areas. This is a good example of adaptation.
(c) Other examples of symbiosis involving microorganisms: Lichens represent a form of symbiotic relationship
between green algae (cyanobacteria) and a fungus. The fungus provides the photosynthetic cells of the algae with
carbon dioxide and water. The fungus also provides structural support. Mycorrhizae are a symbiotic relationship
between the hyphae of a fungus and the roots of a plant. In mycorrhizae, fungal hyphae help the plant absorb nutrients such as phosphorus. Rhizobium bacteria live in the nodules of legume roots. The legume provides the bacteria
with a protected habitat, an energy source for its nitrogen-fixing activities, and the carbon molecules necessary for
the production of organic compounds that contain nitrogen. In return, the bacteria provide the legume with a form
of nitrogen it can use to make proteins.
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