Chapter 5 Quiz

c The blood has nearly a neutral pH, so any organism growing here is a neutralophile.

A bacterial pathogen that can cause septicemia (infection of the blood) is likely Select one: a. an acidophile. b. an alkaliphile. c. a neutralophile. d. a hemophile.

c The relationship between the temperature and the growth rate constant k (number of generations per hour) obeys the Arrhenius equation for simple chemical reactions. The general result of the Arrhenius equation is that growth rate roughly doubles for every 10ºC rise in temperature. Decreasing the temperature 10º from 35ºC to 25ºC should halve the growth rate, leading to one division every 60 minutes instead of 30 minutes.

A mesophile has a growth range between 20ºC and 40ºC, with optimum growth at 35ºC. If the growth rate at 35ºC is one division every 30 minutes, then at 25ºC the growth rate should be approximately Select one: a. one division every 3 minutes. b. one division every 40 minutes. c. one division every 60 minutes. d. one division every 300 minutes.

b The combination of high temperature and high pressure created in an autoclave is effective at killing many bacteria.

A steam autoclave attempts to kill bacteria through a combination of Select one: a. low pH and high temperature. b. high temperature and high pressure. c. high pressure and ionizing radiation. d. ionizing radiation and low temperature.

d A probiotic is a food or nutritional supplement that contains live microorganisms and aims to improve health by promoting beneficial bacteria. Antibiotics are drugs designed to kill bacteria, bioinformatics uses computers to analyze genomes, and phage therapy employs bacterial viruses to kill bacteria.

A woman with irritable bowel syndrome attempts to restore normal intestinal microflora by ingesting yogurt containing live, active cultures. This is an example of using Select one: a. antibiotics. b. bioinformatics. c. phage therapy. d. probiotics.

d Superoxide dismutase removes reactive dangerous oxygen species. The other enzymes listed do not remove reactive oxygen species. In fact, NADH dehydrogenase II can catalyze the formation of reactive oxygen species.

Aerobes may tolerate the presence of oxygen because they have the enzyme Select one: a. DNA gyrase. b. RNA polymerase. c. NADH dehydrogenase II. d. superoxide dismutase.

c Halophiles thrive in high-solute environments. Alkaliphiles grow best in high pH, psychrophiles grow best in cold environments, and barophiles grow under high-pressure conditions.

An organism that grows best at high osmolarity is called Select one: a. an alkaliphile. b. a psychrophile. c. a halophile. d. a barophile.

b Because DNA is a target for irradiation, having less of it means it is less likely to be irradiated. Bacteria usually have smaller genomes than eukaryotic protists and have less DNA per cell unit.

Bacteria have higher D-values for irradiation than protists because Select one: a. bacteria have larger genomes. b. bacteria have smaller genomes. c. bacteria have less cell water per unit volume. d. bacteria have radiation-resistant proteins compared to eukaryotes.

d Barophilic organisms prefer high-pressure environments, such as can be found at great ocean depths.

Barophilic prokaryotes are found primarily Select one: a. on cold mountains. b. in environments enriched in the element barium. c. in the human gastrointestinal tract. d. deep in the ocean.

a The heat shock response is a response to high temperatures. The induction of chaperone proteins helps proteins maintain their correct shape.

Cell changes leading to the production of chaperones that maintain protein shape and enzymes that change membrane lipid composition are known as the Select one: a. heat shock response. b. irradiation response. c. high-pressure response. d. halophile response.

d Temperature changes affect the average rate of molecular motion therefore impacting both the fluidity of membranes and the stability of molecules within bacteria.

Changes in environmental temperature may Select one: a. affect the fluidity of bacterial membranes. b. affect the motion of macromolecules within the bacterial cell. c. affect the stability of molecules within bacteria. d. all of the above

c Eutrophication is the addition of nutrients to an ecosystem. Eutrophication often leads to "blooms," increased numbers of a specific organism. Microbial diversity may decrease as one species outcompetes other species.

Eutrophication may lead to Select one: a. decreased levels of nitrogen. b. decreased levels of phosphate. c. decreased microbial diversity. d. decreased numbers of microbes.

b Extremophilic organisms like archaea have small genomes. Extremophiles grow in environments that are unable to support human life. Extremophiles, although living in various environment, evolved to grow in their specific niche environment, which could be extreme high/low temperature, extreme pH, or salt concentration, etc.

Extremophilic organisms Select one: a. contain an extremely large genome. b. grow in conditions that would be unable to support human life. c. are hypothesized to exist, but have not been documented in the wild. d. often live in environments that are highly unpredictable and subject to extreme temperature changes.

c Halophilic microbes use special ion pumps to excrete sodium and replace it with other cations, such as potassium. In fact, the proteins and cell components of halophiles require high intracellular potassium levels to maintain their structure.

Halophilic archaea can grow at an aw of 0.75 and require 10-20% NaCl to grow. To maintain optimal intracellular Na+ concentration, halophilic microbes Select one: a. use special ion pumps to bring in the additional Na+ required for growth. b. utilize a symport mechanism to bring in additional Na+ along with potassium. c. use special ion pumps to excrete sodium. d. utilize an antiport mechanism to bring potassium in.

d H. pylori employs an exquisitely potent urease converting urea produced by the gastric lining to massive amounts of ammonia, which neutralizes the acid pH environment.

Hylicobacter pylori is a causative agent of gastric ulcers. It survives in the low pH environment of the stomach by Select one: a. actively pumping out protons. b. consuming HCl. c. producing various amino acid decarboxylases. d. secreting urease to generate ammonia.

c Bacteria do not have means to regulate their temperature and equilibrate to the environmental temperature.

If a psychrophilic bacterium that has an optimum growth rate at 14ºC is placed in a 17ºC environment, after a short while the temperature of the bacterial cytoplasm will be Select one: a. 12ºC, as there is an initial undershoot while bacterium tries to regain its optimum temperature. b. 14ºC. c. 17ºC. d. It is impossible to determine what the bacterium's temperature will be.

c Because it will be hard to maintain a proton motive force in an alkaline environment, many alkaliphiles use a sodium motive force as a source of potential energy. Even though alkaliphiles live in alkaline environments, internal proteins do not function well above a pH of 8.

Many alkaliphiles have Select one: a. intracellular proteins that can withstand a pH of 2. b. intracellular proteins that can withstand a pH of 12. c. a sodium motive force. d. triple-stranded DNA as their genetic material.

d Barophiles, which require high pressures to grow, can be found in ocean depths. Since the average temperature at the ocean's floor is 2ºC, many barophiles are also psychrophiles. There is no evidence that it is difficult for enzymes to function at high pressure and above 20ºC as barophilic hyperthermophiles form the basis of thermal vent communities.

Many barophiles are also psychrophilic because Select one: a. it is cold at the high, mountain top elevations where barophiles grow. b. it is difficult for enzymes to function at high pressure and above 20ºC. c. it is usually warm at the ocean depths. d. it is usually cold at the ocean depths.

b Mesophiles grow in moderate temperatures, between 20ºC and 40ºC.

Mesophiles prefer temperatures between Select one: a. 0ºC and 20ºC. b. 20ºC and 40ºC. c. 40ºC and 60ºC. d. 60ºC and 80ºC.

a The human body is at a temperature of about 37ºC, which is preferred by mesophiles. Thermophiles prefer temperatures higher than that of humans and psychrophiles prefer temperatures lower than that of humans.

Most human pathogens prefer temperatures similar to Select one: a. mesophiles. b. thermophiles. c. psychrophiles. d. none of the above.

c Psychrophiles thrive best in cold environments and will be extremely susceptible to high temperatures. Although ethanol and phenol may kill psychrophilic bacteria, they are a chemical means of killing microbes, not a physical means.

One physical means for killing a psychrophilic bacteria is Select one: a. ethanol. b. phenol. c. high temperature. d. low temperature.

c At high temperatures, noncovalent bonds responsible for protein secondary and tertiary structure will break leading to protein denaturation. Other changes at high temperatures are increased membrane fluidity and increased diffusion rates.

One reason most organisms cannot grow at high temperatures is that Select one: a. membranes will stiffen. b. diffusion rates slow down. c. proteins denature. d. DNA base pairs become too stable.

a Strict aerobes can only use oxygen as a final electron acceptor in their electron transport chains. Although aerobes can grow in the presence of oxygen, they do not necessarily use oxygen as the final electron acceptor in the electron transport chain. Anaerobes do not use oxygen and strict anaerobes are killed by oxygen.

Organisms that must use oxygen as a final electron acceptor in electron transport chains are Select one: a. strict aerobes. b. aerobes. c. anaerobes. d. strict anaerobes.

c Oligotrophic environments are low in nutrients. Heterotrophs are organisms that must obtain reduced carbon from their environment. Hypotroph and mesotroph are made-up terms and are not used to describe any group of microorganisms.

Organisms with a high rate of growth at low nutrient concentrations are called Select one: a. hypotrophs. b. mesotrophs. c. oligotrophs. d. heterotrophs.

d Pasteurization relies on high heat, a physical way to kill microbes.

Pasteurization limits microbial numbers through Select one: a. chemical means. b. filtration. c. refrigeration. d. high heat.

b Piezophiles is a synonym for barophiles, referring to organisms that require high pressures for growth.

Piezophiles are also known as Select one: a. alkaliphiles. b. barophiles. c. halophiles. d. psychrophiles.

d A protein works best at a particular temperature, pH, and osmolarity. Different proteins may have different optima for these variables.

Proteins have optima for Select one: a. temperature. b. pH. c. osmolarity. d. all of the above.

b Both psychrophiles and mesophiles can grow over about a 20ºC temperature range, but the range is shifted down to colder temperatures for psychrophiles. Because decreased temperatures stiffen proteins, psychrophiles' proteins need to be more flexible. Decreased temperatures make membranes less fluid, so psychrophiles have membrane lipids that enhance fluidity. Psychrophiles also tend to produce fewer generations per hour than mesophiles.

Psychrophiles tend to have Select one: a. more membrane lipids that enhance membrane stiffening than mesophiles. b. more flexible proteins than mesophiles. c. faster growth than mesophiles. d. a wider temperature growth range than mesophiles.

a Archaea have been found in the most extreme (by human standards) conditions. Eukaryotes, such as plants, are least able to tolerate extreme conditions.

The most extremophilic organisms are Select one: a. archaea. b. bacteria. c. eukaryotes. d. plants.

c Phages are viruses that infect and may kill bacteria. With the emergence of many antibiotic-resistant strains of bacteria, the idea that phages can be used to kill bacteria is gaining renewed interest.

The term "phage therapy" refers to Select one: a. the presence of "good" bacteria such as lactobacillus in yogurt. b. the use of light energy (photons) to cure viral diseases. c. the idea that phages could be used to treat bacterial diseases. d. none of the above.

b Even halophiles require low intracellular sodium as an inward sodium gradient is often used to transport other molecules into the cell. The other molecules listed can be accumulated intracellularly to lower a cell's osmolarity.

To maintain water balance in a hypertonic environment, some microorganisms accumulate intracellular solutes. Which molecule would NOT be used as a cytoplasmic solute? Select one: a. Glutamic acid b. Sodium ion c. Potassium ion d. Proline

b As osmolarity increases, the increasing solutes hold water and decrease the water activity.

What is the relationship between osmolarity and water activity? Select one: a. There is a positive correlation; as osmolarity increases water activity also increases. b. There is a negative correlation; as osmolarity increases water activity decreases. c. There is a positive correlation and the magnitude of the correlation is temperature dependent. d. There is no correlation between osmolarity and water activity.

a Barophiles grow under high pressure. The other organisms listed are not considered extremophiles.

Which of the following is an extremophile? Select one: a. A barophile b. A mesophile c. A microaerophile d. A neutralophile

b The correct definitions are: · Disinfection removes pathogens from inanimate objects. · Sterilization kills all cells, spores, and viruses on an object. · Antisepsis removes pathogens from the surface of living tissues.

Which of the following sentences is correct? Select one: a. Sterilization kills all cells, spores, and viruses on an object; antisepsis removes pathogens from inanimate surfaces; and disinfection removes pathogens from the surface of living tissues. b. Sterilization kills all cells, spores, and viruses on an object; disinfection removes pathogens from inanimate surfaces; and antisepsis removes pathogens from the surface of living tissues. c. Disinfection kills all cells, spores, and viruses on an object; sterilization removes pathogens from inanimate surfaces; and antisepsis removes pathogens from the surface of living tissues. d. Disinfection kills all cells, spores, and viruses on an object; antisepsis removes pathogens from inanimate surfaces; and sterilization removes pathogens from the surface of living tissues.

a In a hypertonic solution, water will flow out of the bacteria by osmosis. This will decrease cell volume. In a hypotonic solution, water will flow into a bacterium by osmosis. In an isotonic solution, the bacterium is at water equilibrium with its environment.

Which of the following sentences is true? Select one: a. If a bacterium's cell volume decreases after it is placed in solution A, then solution A is hypertonic relative to the bacterium. b. If a bacterium's cell volume decreases after it is placed in solution A, then solution A is hypotonic relative to the bacterium. c. If a bacterium's cell volume decreases after it is placed in solution A, then solution A is isotonic relative to the bacterium. d. If a bacterium's cell volume decreases after it is placed in solution A, then solution A is thermotonic relative to the bacterium.

a Although each species has an optimal temperature for maximum growth, for each species temperature and growth show a positive correlation. As temperature increases, reactions tend to speed up, increasing metabolism and growth.

Within temperatures allowable for growth, higher temperatures usually lead to Select one: a. higher growth rates. b. slower growth rates. c. no effect on growth rates. d. The effect depends on the species.