Microbiology: An Evolving Science 5th Edition by Joan L. Slonczewski test bank

 Previously, it was believed that the conversion of grapes and grain to wine and beer was a spontaneous chemical process. Pasteur discovered that this fermentation was caused by living yeast, which did not require oxygen for growth. He also discovered that when the grapes or grain are contaminated with bacteria instead of yeast, acetic acid is produced instead of alcohol.

 Answers may vary. Some examples include bubonic plague, which killed one-third of Europe’s population in the fourteenth century; tuberculosis, which was common in the nineteenth century; human immunodeficiency virus, which affects many people today; and smallpox, which killed a large number of native North Americans.

 Microbes are too small to be seen with the naked eye, so until powerful-enough microscopes were invented, humans did not know that microbes existed. Even after humans were aware of the presence of microbes, they did not suspect them of causing disease until people such as Joseph Lister and Ignaz Semmelweis performed experiments that showed that antiseptics decrease the incidence of infection and then Koch demonstrated that a particular organism was the cause of a specific disease.

 Answers may vary, but a major reason is that humans cannot be injected with HIV to see if they develop AIDS and no suitable animal host exists for testing.

 Attenuation results in a weakened organism that will not produce full-blown disease, but will generate immunity. Answers for mechanisms may vary, but heat treatment, aging for various periods, and natural attenuation in the host are mentioned in the chapter.

 They showed that use of antiseptics on doctors’ hands and medical instruments drastically reduced the mortality rate of hospital patients. They made these observations before Robert Koch advanced the germ theory of disease.

 See Figure 1.19 in the textbook:
(1) The suspected organism is found in all cases of the disease but is absent from healthy individuals.
(2) The suspected organism is isolated from the diseased host and grown in pure culture.
(3) When the suspected organism is introduced into a healthy host, the same disease occurs.
(4) The same strain of microbe found in the originally diseased host is obtained from the newly diseased host.

 The organisms studied by Winogradsky were lithotrophs, which feed solely on inorganic substances. Koch’s plate media contained organic nutrient sources, which may even be toxic to the organisms he was attempting to grow.

 No, this is not a true statement. It is estimated that barely 0.1% of microbial species can be cultured. The work of Winogradsky and later microbial ecologists showed that bacteria are necessary for geochemical cycling. Many of these organisms cannot be grown in pure culture on laboratory media but can be grown in enrichment culture such as a Winogradsky column.

 An endosymbiont is an organism living symbiotically inside a larger organism. Examples may vary, but include the following: Rhizobium in a leguminous plant, bioluminescent bacteria in the light organs of fish and squid, and photosynthetic algae and coral.

 First, even with the use of light microscopes, only the basic shape of microbes can be determined, and many microbes have similar shapes even though they are very different in other ways. Second, microbes do not fit the classic definition of a species, which is a group of organisms that interbreed. Microbes typically reproduce asexually. When they do exchange genes, they may do so with distantly related species.

 The endosymbiosis theory proposes that mitochondria and chloroplasts evolved from bacteria that were engulfed by pre-eukaryotic cells, and that over time these endosymbiotic prokaryotic cells lost the ability to survive outside the host cell but were instead maintained as organelles. Evidence supporting the endosymbiosis theory includes the fact that mitochondria and chloroplasts possess circular DNA with a similarity to modern bacteria.

 Franklin was an X-ray crystallographer who studied the structure of DNA. Her X-ray micrographs showed for the first time that DNA was a double helix. A colleague showed her micrographs to James Watson, who was also studying the structure of DNA. Watson and Francis Crick published their model of the structure of DNA in the journal Nature and denied that they had used Franklin’s micrographs. Franklin also died before the awarding of the prize.

 The ultracentrifuge uses centrifugal forces to separate cell components. Theodor Svedberg calculated that the particle sizes could be determined based on the rate of sedimentation of the particles in an ultracentrifuge.

 Since DNA polymerase in PCR must survive many rounds of cycling to near-boiling temperatures, the most conducive environment for finding DNA polymerase, such as the enzymes used in PCR reactions, would be searching for microbes in an environment where the temperature is extremely high, such as the hydrothermal vents in the oceans.