microbes in the flask media after sterilization, despite the presence of the swan necks. 40 .So many of the genes
originally contained in the chromosomes of the bacteria from which these organelles arose have been transferred to
the host nuclei, so these organelles no longer have a full complement of genes available to code for themselves
independent of the host cell. The modern-day organelles need nuclear genes to function. 41 .Snow was the first to
use epidemiology, tracing the incidence of disease and mapping it to locate its source. In doing so, he was able to
determine that cholera was caused by fecally contaminated water. This was an important step in the development of
the germ theory and clearly refuted the prevailing miasma theory of that time. His work also resulted in the first
public health response to an epidemic, which was successful. 42 .(a) fimbrae, (b) cytoplasm, (c) nucleoid, (d)
flagellum, (e) cell wall, (f) plasma membrane 43 .d 44 .Any component found only in bacteria would be a good
target. Common antibiotic targets include peptidoglycan, found in bacterial cell walls, and the bacterial ribosome,
because it is structurally distinct from the eukaryotic cytoplasmic ribosome. 45 .The bacterium would be difficult to
kill because it would form endospores to survive harsh conditions, such as the high temperatures of cooking or
boiling, dehydration, ultraviolet radiation, or chemical exposure. For this reason, the food industry must follow
carefully designed protocols to process preserved foods that may contain these bacteria or their endospores. 46 .A.
plasma membrane; B. nucleus; C. nucleolus; D. mitochondria; E. centrioles; F. endoplasmic reticulum; G. Golgi
apparatus; H. flagellum 47 .Peroxisomes grow through the incorporation of peroxin proteins synthesized by free
ribosomes in the cytoplasm. When large enough, they divide by binary fission, similar to mitochondria. They differ
from mitochondria in their function and, unlike mitochondria, they contain neither their own DNA nor their own
ribosomes. 48 .Both of these organelles contain components that are used for the degradation of molecules.
Lysosomes contain digestive enzymes that degrade engulfed foodstuffs, infectious agents, and damaged cellular
constituents. Peroxisomes contain hydrogen peroxide, which is a strong oxidizing agent that aids in the breakdown
of uric acid, amino acids, and fatty acids. If the contents of these organelles were not contained within membranes,
they would damage cytoplasmic components within cells.
Chapter 4
1 .B 2 .C 3 .B 4 .A 5 .A 6 .D 7 .C 8 .B 9 .D 10 .A 11 .A 12 .B 13 .B 14 .D 15 .B 16 .True 17 .parasitism
18 .Eukarya 19 .antibiotic 20 .ammonia 21 .obligate 22 .Helicobacter pylori 23 .Gammaproteobacteria
24 .Treponema pallidum pallidum 25 .purple nonsulfur 26 .genus 27 .pyogenic 28 .high 29 .distance 30 .common
ancestor 31 .vents 32 .ionizing radiation 33 .Sulfolobus 34 .Methanobrevibacter oralis 35 .Commensalism is a
relationship between two organisms in which one benefits and the other is unaffected. Amensalism is a relationship
between two organisms in which one is unaffected and the other is harmed. 36 .Long-term treatment with antibiotics
can change the vaginal microbiota. If acid-producing bacteria (e.g.,Lactobacillus) are eliminated by antibiotics, the
less-acidic vagina becomes populated by yeasts. 37 .Coliforms ferment lactose completely, producing acid and gas.
Noncoliforms either can’t ferment lactose or ferment incompletely. Several species of intestinal pathogens are part
of the noncoliform group. 38 .They are unable to produce ATP and are metabolically inactive outside of host cells.
They are only able to replicate inside host cells, where they can use the intracellular ATP. 39 .CFB group is a large
nontaxonomic group of gram-negative nonproteobacteria that includes the generaCytophaga,Fusobacterium, and
Bacteroides. 40 .Borrelia burgdorferi, a gram-negative nonproteobacterium in the Spirochaetae, infects arachnoids
(ticks) and can be transmitted to humans by tick bites. It is a fastidious bacterium, which is extremely difficult to
culture. Microscopically, it looks like a very thin spiral. 41 .The phylum Cyanobacteria is a large group of aquatic
bacteria known for their blue-green pigment and ability to produce large amounts of gaseous oxygen during
photosynthesis. Cyanobacteria play a major role in the maintenance of oxygen content in our planet’s atmosphere.
42 .methicillin-resistantS. aureus(MRSA) and vancomycin-resistantS. aureus(VRSA). These two typesS. aureus
are resistant to multiple classes of antibiotics, which makes treatment of infections challenging 43 .Deeply
branching bacteria provide scientists with clues as to the nature of life on earth billions of years ago. In industry,
some of them are used for molecular hydrogen production. 44 .the unique mechanisms of DNA repair
45 .photosynthesis that uses bacteriorhodopsin 46 .Samples of the Martian atmosphere contain the gases produced
272 Answer Key
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