Download Suggested Answers for Insight Questions, Foundations in

Suggested Answers for Insight Questions, Foundations in Microbiology,
7th Edition, listed by chapter, number, and page location.
A note to the users of these answers: These answers discuss some of the possible ways to
approach the questions. They are not meant to be exhaustive in depth, but can offer information,
suggestions, and points of view that will be helpful in understanding some of the concepts
covered in the Insight and the chapter. Furthermore, they are not the final word--you may have
thought of some other explanations that are just as valid. It is hoped they will serve to stimulate
class discussion and inspire further research.
12.1, pg. 349 – From Witchcraft to Wonder Drugs
First thing would be to collect some seawater in coconut shells and allow it to dehydrate
so that it became quite salty. (Regular seawater alone may not be salty enough). Salt is a
good inhibitor of most microbes, and it could safely be placed on skin or used as a gargle
or mouthwash. Speaking of coconuts, coconut milk is a fantastic substance with many
healthful properties. An unbroken coconut stays sterile inside, so it is automatically free
of microbes. It is actually used in some cultures to treat diarrhea, similar to oral
rehydration solution. It also contains a variety of fatty acids, many of which have
properties that act against viruses, protozoa, fungi, and bacteria, so it could be used orally or on
skin lesions. I would try to start a fire to boil fresh water, so that I would have disinfected water to
drink and wash with. The charcoal from the fire could be used as well to filter water and used to
make a paste for wounds. Charcoal is known to have some antimicrobial powers and could be
ingested in small amounts to treat gastroenteritis. I would search over the desert island and find
plant leaves, bark, and other materials. I would use plant materials with caution, but try small
amounts on skin to test for possible effects. All leaves contain chlorophyll, which can be
inhibitory to some infectious agents. Being a microbiologist, I might try to culture various native
molds on coconut meat, and test them to see if they can kill bacteria. Sounds like the professor
on Gilligan's Island!
12.2, pg. 357 – A Modern Quest for Designer Drugs
Drug research and development (R and D) is time intensive because of the numerous steps in
the process. First, a new potential drug must be discovered through extensive testing, chemically
characterized, and purified. It could be an antibiotic derived from microbes, plants, or animals, or
a synthetic compound created in a laboratory. This step alone could easily take 5 years or
more. Then the precise effects of this drug--its mode of action--must be analyzed and tested on a
wide variety of microbes, usually in vitro. Sometimes the drug will be modified chemically
(semisynthesized) to improve its effectiveness. This stage of testing could take another 3-5
years. The effect of the drug on living animals (in vivo) would be the next test, partly to determine
effectiveness and partly for potential side effects and toxicity--another 3-5 years. If the drug does
not work, it may be sent back for further R and D and may have to be abandoned even after
several years. If it passes the tests on experimental animals, then it undergoes several phases of
clinical trials on humans, often using double blind and placebo testing to ensure its scientific
accuracy. These clinical trials can take 5 to 7 years, and only when the drug has been approved
by the Food and Drug Administration (FDA) can it be available for therapy. The length and
expense of R and D is a major reason that drug companies are given lengthy patents on their
drugs, and why drugs can be so expensive.
12.3, pg. 365 – Household Remedies – From Apples to Zinc
The main positive aspects of using natural foods, herbs, or other alternative therapies is that they
have very few of the adverse side effects that many processed drugs have. They are often
substances such as garlic or yogurt that are normally eaten in large quantities and are nontoxic
and harmless. They would also be less likely to cause allergies or disturb the normal flora. In
fact, the probiotic bacteria present in active culture yogurt are known to stabilize the normal flora.
The problem of drug resistance can be side-stepped entirely. With natural products, one may
also be ingesting useful nutrients rather than just a pure chemical. One attitude about home
remedies is “try it, and if it works, then great; if it doesn’t work, no harm done.” Take for example
using Vicks vaporub on toenail fungus or duct tape on warts. Neither substance will do any harm
and yet for many people they are highly effective treatments. One should still be careful ingesting
exotic herbs and potions with unproved or untested claims, especially since one does not always
know their complete contents.
12.4, pg. 370– The Rise of Drug Resistance
The primary reasons are that microbes 1) have very short generation times, which allow for rapid
expansion of the population and the gene for drug resistance; 2) are very adept at acquiring and
using genes obtained from other microbes; and 3) readily adapt to beneficial mutations of their
own genomes that favor survival. For example, if a bacterium, say E. coli is living in the large
intestine of a cow that harbors a drug resistant Salmonella, it is possible for a cell of E. coli to
acquire the gene for drug resistance through conjugation with Salmonella. Note that it takes only
a single instance of this to create drug resistance. The scene is set when the cow is given feed
with the drug added to it. The environment of the intestine will now contain that drug, and the E.
coli cell that has become resistant is not affected by it. It now grows in the presence of the drug,
easily expanding its population from a single cell to several billion cells in a few hours. Then if
the cow's milk or meat becomes fecally contaminated, the E. coli (not to mention the Salmonella),
may be ingested with milk or meat that are not properly disinfected. The drug resistance does not
end with that cow, since cattle can pick up drug resistant bacteria from grazing and contaminated
water.