question

In mesophiles, growth rates increase gradually as the temperature is increased, until the optimum growth temperature for the organism is reached. If the temperature is increased beyond the optimum, __________.

answer

growth rates decline rapidly as the temperature increases

question

Bacteria that are able to grow in humans and cause disease have likely evolved to be

answer

mesophiles

question

Most mesophilic organisms can grow in a temperature range of

answer

20-40°C.

question

A microbe growing in a refrigerator is likely

answer

psychrotolerant or psychrophilic.

question

One reason food is refrigerated to control microbial growth is because irreversible cell damage is more likely to occur at low rather than high temperatures.

answer

False

question

The optimum temperature is usually closer to the minimum temperature than the maximum temperature.

answer

False

question

Which statement illustrates the chemical basis for the predominant type of fatty acids in the plasma membrane of a psychrophile?

answer

Unsaturated fats have kinked side chains that prevent tight packing as temperatures drop.

question

Relative to enzymes in mesophilic microorganisms, which of the following is NOT characteristic of enzymes in psychrophiles?

answer

less ionic bonds

question

A bacterium such as a snow alga that is able to survive a cold temperature is called a psychrophile.

answer

False

question

Which statement shows which adaptations are necessary for hyperthermophilic proteins to stay functional at temperatures above 80Â°C?

answer

Hyperthermophiles have increased ionic bonds to stabilize the proteins.

question

Which of these statements is/are TRUE?

answer

Nonphototrophic organisms are able to grow at higher temperatures than phototrophic organisms. In general, prokaryotic organisms can grow at higher temperatures than eukaryotic organisms. The most thermophilic prokaryotes are species of Archaea. ---- All of the statements are true.

question

Some microbes can grow in boiling water.

answer

True

question

Due to the relationship between the rate of enzyme catalysis and temperature, organisms living in boiling hot springs are also rapid growers with fast doubling times.

answer

False

question

Taq polymerase was isolated from a thermophile and is used in the polymerase chain reaction (PCR) technique because it does not become inactivated at high temperatures.

answer

True

question

Where would it be best to isolate bacteria from to study the mechanism of the sodium motive force?

answer

soda lakes

question

Consider solution A (pH 6) and solution B (pH 9). Which of the following statements is CORRECT?

answer

Solution B is 1,000 times more alkaline (basic) than solution A.

question

In principle, the chemical composition of membranes in obligate acidophiles could be distinguished from neutrophiles.

answer

True

question

A bacterium's pH optimum reflects the optimal pH of its intracellular environment.

answer

False

question

The ratio of the vapor pressure of the air in equilibrium with a substance to the vapor pressure of pure water is known as

answer

water activity.

question

Organisms able to live in environments with high sugar concentrations are

answer

osmophiles.

question

When water activity is low, an organism must

answer

increase its internal solute concentration.

question

The sensitivity of DNA and RNA is one major reason water activity can limit microbial growth.

answer

False

question

The addition of thioglycylate into a growth medium would NOT support the growth of a(n)

answer

microaerophilic aerobe.

question

A bacterium containing ________ provided with hydrogen peroxide will produce oxygen bubbles.

answer

catalase

question

Which of the following forms of oxygen is/are generally toxic to living organisms?

answer

superoxide, hydrogen peroxide, and hydroxyl radicals are all toxic

question

A non-aerated or shaken liquid growth medium inoculated with a bacterium is one of the best ways to culture an obligate anaerobe.

answer

False

question

Which of the following shows the moist heat methods in order of the temperature used (highest to lowest)?

answer

Ultrahigh;Autoclave;Boiling;Batch Pasteurization

question

_______________ is a process used to destroy pathogens in food and drinks. It must be done at a lower temperature than other methods so that _______________.

answer

Pasteurization; the taste of the food or drink will not be altered

question

During a flood, a community's well water system is contaminated with a pathogenic fungus. If the residents boil their water for 15 minutes prior to consumption, will they be protected?

answer

yes, most likely

question

What temperature is most commonly used for autoclaves to sterilize growth media and other devices prior to experimentation?

answer

121°C

question

An unpressurized autoclave would not be able to sterilize a growth medium with contaminating bacteria but could still pasteurize it.

answer

True

question

A microbiologist wants to study the virus particles from a urine sample, but not any bacteria that might be present. How can the bacteria be eliminated without harming the viruses?

answer

Filter the sample with a 0.2 ïm pore filter.

question

Your laboratory supervisor has given you a plastic petri dish filled with soil to sterilize using radiation. What type of radiation will you use?

answer

ionizing radiation

question

Many aromatic compounds used for growth substrates by bacteria are broken down during high heat autoclaving. Which is the BEST way to sterilize these aqueous solutions?

answer

0.2 ?m filter sterilization

question

Sterility of a laminar flow hood is accomplished by filter-sterilized air passed through the hood quickly enough that non-sterile air does not flow into the work area.

answer

True

question

The major distinguishing difference between antiseptics and disinfectants is __________.

answer

antiseptics can be used on living tissue

question

What does the minimum inhibitory concentration (MIC) of a chemical tell you?

answer

It tells you the smallest concentration of the chemical that is needed to inhibit the growth of a specific microorganism.

question

The MOST effective antibiotics in preventing growth of disease-causing bacteria are

answer

bacteriolytic or bacteriocidal.

question

The L-form B. subtilis bacteria described in the introductory passage have a spherical shape and pattern of growth that is very different from non-mutant B. subtilis, which is a rod-shaped bacterium. What best explains the difference in appearance and shape?

answer

A sphere is the most energetically favorable shape for a cell.

question

Hyperthermophiles are organisms that thrive at extremely high temperatures. What sorts of specializations might they have to survive in such high temperatures?

answer

extremely heat stable proteins that function best at high temperatures increased use of isoprene units instea of fatty acids cell membranes with long chain fatty acids monolayer membranes that link one side to the other for stability

question

L-form bacteria rely on their cell membrane as their protection from the external environment, determining what can move in and out of the cell. Bacteria with cell walls have additional protection, but need to synthesize the peptidoglycan precursors within the cell and then transport them across the membrane to maintain or expand the cell wall. The peptidoglycan precursors require assistance in moving across the membrane, which is accomplished by a hydrophobic molecule called bactoprenol. Why is it important for peptidoglycan precursors to be sufficiently hydrophobic in order to cross the cell membrane?

answer

The hydrocarbon tails in the phospholipid membrane are hydrophobic, so it is easier for hydrophobic materials to pass through the membrane.

question

Microbes are found at a wide range of temperatures, from the cold in the Antarctic to hot springs like those at Yellowstone National Park. In the introductory passage, B. subtilis is discussed because it has been used as a model organism. B. subtilis is a bacterium normally found in the human gut and can sometimes cause disease. An autoclave is often used at a temperature of 121°C, which is close to the maximum temperature for most Archaea (122°C). What is likely to be an optimal temperature for the growth of B. subtilis?

answer

The optimal temperature for the growth of B. subtilis is 36-38°C. B. subtilis is considered a mesophile.

Microbiology Exam 2 Growth Conditions – Flashcards

Unlock all answers in this set

Haven't found what you were looking for?

Search for samples, answers to your questions and flashcards