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Downey, LBCC Microbiology Exam 2 Study Guide

Pathogenic bacteria are classified as _____________ for their growth temperature requirements.

mesophiles

An organism that you are studying grows at 4°C and at 25°C. However, it grows best at 20°C. This organism would be classified as a:

psychrotroph

Through metabolism pathogens often produce acids that interfere with their own growth. ________ are added to media to control pH changes.

Buffers

Which of the following are mismatched? Hyperthermophiles :

no water

Bacteria require nitrogen for the synthesis of:

proteins.

Trace elements are added to microbiological media to provide:

cofactors.

Which of the following is not a chemical requirement of all bacteria?

Molecular oxygen

An organism that grows both in the presence and the absence of oxygen and uses oxygen when it is available is called a/an:

Facultative anaerobe.

A culture medium consisting of agar, peptone and beef heart extract is a/an:

complex medium.

Which of the following is not a component of a defined media.

peptone

Which of the following types of media is designed to suppress the growth of unwanted bacteria and encourage the growth of desired microbes?

Selective media

Niacin, when added to a medium, would be considered a/an:

organic growth factor.

Which of the following is not a step in binary fission?

Lysis of the existing cell wall.

If a single bacterium replicated every 30 minutes, how many bacteria would be present in 2 hours?

16

In which phase of the growth curve is the population doubling time fastest?

Log phase.

During the lag phase:

cells are engaged in intense enzymatic activity.

What phase of the cell cycle is extended in a chemostat?

Log phase

All of the following are true of the plate count method except:

Fast-completed in minutes.

An unknown culture is assayed via the plate count method. After dilution of cells and incubation, no colonies are observed. Which of the following is not a possible explanation?

The bacterial cells formed invisible colonies.

Blood agar used to observe hemolysis or clearing around Streptococcus pyogenes colonies is an example of a/an:

differential media.

Shrinking of the cell's cytoplasm in response to osmotic loss of water is called __________.

plasmolysis

The ability of microbes to utilize N2 as a nitrogen source is called __________.

nitrogen fixation

The enzyme __________ catalyzes the conversion of peroxide to water and oxygen.

catalase

The __________ is the most common technique used to obtain pure cultures of microbes. (3 words)

streak plate method

Bacterial growth refers to an increase in the __________ of bacterial cells.

number

An unknown organism grows at the top of a tube of thioglycolate broth. This organism is best described as a/an __________ for its oxygen requirements.

aerobe strict aerobe

Salt agar tends to inhibit the growth of most organisms, except Staphylococcus. This is an example of a/an __________ media.

selective

In a/an __________, cells are added to melted agar and poured into a petri dish. (2 words)

pour plate

A type of cell-to-cell communication that allows bacteria growing in biofilms to communicate and coordinate their activity is known as __________. (two words)

quorum sensing

In a pour plate technique, 32 bacterial colonies are counted on the 10-2 dilution of milk. How many bacteria were in the original milk? __________. (Do not use scientific notation in your answer.)

3200

Psychrotrophic organisms are often responsible for food spoilage in refrigerated foods.

True

Adding salts to a solution increases osmotic pressure and is used to preserve food.

True

Microaerophiles do not require oxygen for growth.

False

Aerotolerant organisms can grow in the presence of oxygen because their cell wall protects them from toxic products of oxygen.

False

During the stationary phase, bacteria continue to undergo binary fission.

True

Candle jars work well for cultivating anaerobic bacteria.

False

When the spread plate technique is used to inoculate culture media, some colonies form within the agar.

False

In a direct microscopic count, dead cells are easily differentiated from live cells.

False

Turbidity, or cloudiness, of cell cultures measured by spectrophotometry is useful in detecting small amounts of microbial contamination in liquids.

False

Cells growing in a rich medium will have a steeper log phase slope than will those growing in a nutrient-poor medium.

True

The growth curve pictured best depicts ________.

a mesophile incubating at 37° C

What causes a bacterial culture to enter the stationary phase?

depletion of nutrients and accumulation of waste products

During which phases of the bacterial growth curve are there no changes in the number of living cells?

lag and stationary

Which of the following situations will lead to food being in the "danger zone," with the potential for food poisoning?

Five pounds of homemade potato salad, refrigerated overnight in one huge bowl, and served without any cooling on a warm summer day.

In this graph, the x-axis represents the number of generations. If this axis is changed to time, how would that change affect the slope of the logarithmic graph for different bacteria? Assume that the time scale for each graph is the same.

Faster-growing bacteria would have a greater slope than would those with a slower generation time.

What would be a disadvantage of using turbidity estimation to determine the number of viable bacterial cells in a broth culture?

The turbidity method "counts" dead cells as well as those that are viable, and the turbidity method cannot be used on very dilute populations.

Sterilization is the ________.

destruction of all life-forms

An antiseptic is used to remove microbes from ________.

skin, before an injection

Which of the following infectious agents challenges current sterilization strategies that have been accepted and in use for decades?

prions

Some antimicrobial treatments kill microbes; some inhibit growth. Which term refers to an agent that inhibits bacterial growth?

bacteriostatic

Which of the following is not a major target for action of antimicrobials?

flagella

You contaminate the kitchen counters with Salmonella enterica in chicken blood and expose it to a variety of treatments to study the survival of the bacteria on kitchen surfaces. The following DRT values were obtained: 2.0 min. at 52°C; 3.7 min. at pH 2.6; 13.3 min. with 10 mM hydrogen peroxide; and > 35 days without treatment. Which treatment is most effective against S. enterica?

heat (52°C)

Which of these is not a characteristic of the autoclave?

the requirement for long (hours) exposure times

Pasteurized milk in an unopened container spoils in the refrigerator. A sample reveals the presence of microorganisms. The most likely explanation is ________.

the microbes that survived pasteurization were able to grow at 4°C.

Pasteurization was first used by Pasteur to control spoilage of ________.

wine

You are preparing a medium for growing fastidious bacteria and must add several heat-labile solutions of growth factors. Which of the following is an appropriate strategy for preparing and sterilizing this medium?

Prepare and autoclave the medium before adding the growth factors. After the medium has cooled, filter sterilize and aseptically add the growth factors.

Which of the following is least likely to be damaged by exposure to gamma radiation?

prions

Packages of milk and coffee creamers may be stored without refrigeration if they have been sterilized by ________.

ultra-high-temperature (UHT) treatment

All of the following methods are used for food preservation except ________.

direct flaming

Some microbes are very resistant to antimicrobial chemicals. Which of the following would be the easiest to kill?

E. coli.

Which type of radiation is least effective in killing microbes?

microwaves

The DRT for a particular bacterial species at 60°C is 30 minutes. How long would it take at this temperature to remove 99.9% of this bacterial population?

90 minutes

Alcohol is most effective when used as a ________ solution.

70%

All of the following are examples of microbial control using heavy metals except ________.

benzoyl peroxide used for acne treatment

________ is a compound found in antimicrobial soaps that targets gram-positive bacteria.

Triclosan

The following may be listed on the ingredients of your favorite snack food. Which of these products is not antimicrobial?

xanthan

The more microbes present in a sample, the __________ it takes to eliminate the microbial population.

longer, more time

The decimal reduction time is the time required to kill __________ percent of a bacterial population.

90

Moist heat kills microbes by __________ of cellular components.

denaturation

__________ is a common household disinfectant that has been used to disinfectant everything from dairies to drinking water.

bleach

A zone of growth inhibition around a copper penny on a plate that had been swabbed with bacteria demonstrates the __________ of copper.

oligodynamic action, oligodynamic effect

__________ has little value as an antiseptic but is important in the mechanical removal of microbes.

soap

Oxidizing agents, such as hydrogen peroxide, are useful for irrigating deep wounds where released oxygen will inhibit the growth of __________.

anaerobic bacteria, anaerobes

__________ bacteria may survive pasteurization.

Thermoduric, Endospore-forming, Heat-resistant

Operating rooms may receive ventilation from air that has passed through __________ filters to remove microorganisms.

HEPA, high-efficiency particulate air

__________ ammonium compounds are less effective against gram-negative bacteria and more effective against gram-positive bacteria.

Quaternary

Most viruses are highly resistant to disinfectants and antiseptics.

False

The presence of organic matter, such as blood or saliva, may impair the action of antimicrobial chemicals.

True

All bacteria die at once when they are exposed to heat or chemical treatment.

False

Times required for sterilization in an autoclave are shorter than those required in a dry oven because moist heat penetrates biological specimens more effectively than does dry heat.

True

Ethylene oxide gas is used to sterilize medical equipment that might be damaged by exposure to the heat of autoclaving.

True

UV radiation and x-ray radiation are similar in that they damage DNA and have a high penetrating power.

False

Iodine is one of the least effective antimicrobial chemicals, effective only against certain very sensitive strains of bacteria.

False

Soap is ineffective in killing bacteria. Therefore, hand washing is a rather ineffective measure in preventing disease transmission.

False

Ionizing radiation can be used to sterilize some foods such as spices, meat, and fruits and vegetables.

True

Which of the following factors influences the rate at which heat or chemicals kill bacteria?

all of these. exposure times, types of chemical, temperature.

You have two populations of cells that you want to kill. The first has 100,000 cells per ml, and the second has 1,000,000 cells per ml. Which will be killed at a faster rate?

Both populations will be killed at the same rate.

Put the following in order from least to greatest amount of time to kill the population using a chemical agent:

gram-negative bacteria, gram-positive bacteria, endospores, mycobacteria. gram-positive bacteria, gram-negative bacteria, mycobacteria, endospores

A new soil microorganism has been described. On some growth media, it forms colonies of unicellular organisms; but under certain conditions it forms long, multicellular filaments and spores. The cells have nuclei, and their cell walls are composed of chitin. To which of the following groups does this new organism belong?

fungi

Unicellular, nonfilamentous fungi are known as ________.

yeasts

In the 1990s a new parasitic helminth was described in a 3-year-old boy. The only unusual part of his history was that he played in a shed frequented by raccoons. To diagnose the child's behavioral changes and loss of speech and motor skills, doctors did MRIs and CT scans. The data collected from these scans suggested the presence of larval helminths in his brain. Which of the following is the most likely scenario?

Raccoons are the definitive hosts, and humans are accidental intermediate hosts.

All of the following answers are true of the fungi except ________.

they are strict aerobes

Fungi are ________.

chemoheterotrophs

Fungal spores ________.

are considered "reproductive" spores

All of these answers are true of yeasts except ________.

they always cause disease

Four days after playing in the wading pool at a neighborhood park, several 3- and 4-year-old children experienced abdominal cramping and watery diarrhea. Upon microscopically examining the children's stools with an acid-fast stain, doctors found red, cystlike structures about 10 microns in diameter. What is the most likely diagnosis?

infection with Cryptosporidium spp.

Which of the following is not involved in the production of sexual spores in fungi?

fragmentation

Which of these answers is true for the trematodes?

They may have more than one intermediate host.

Which structure is not found in cestodes?

intestine

A fungus that produces sporangiospores and zygospores and has hyphae without cross-walls would be classified in the category ________.

Zygomycota

Lichens ________.

are organisms made of a fungus and a photosynthetic partner

In a lichen, ________.

the fungus appears to make the plasma membrane of the photosynthetic partner more permeable

You observe large (> 10 μm) oval cells in a sputum sample from a patient. Your culture of the sample reveals fuzzy filamentous colonies. You conclude that ________.

the patient has an infection caused by a dimorphic fungus

A unicellular alga with cell walls containing pectin and silica is isolated from coastal waters. It is capable of photosynthesis and stores oil for energy. This alga is most likely a ________.

diatom

Which answer is an incorrect match?

hookworm; incomplete digestive system

Which answer is an incorrect match regarding motility?

Euglenozoa; nonmotile

Which of these answers is true of the Apicomplexa?

Enzyme-containing organelles are present at one end.

You are an epidemiologist studying an emerging disease reported over the past 3 years in Wisconsin, Minnesota, and Michigan. You have noticed a seasonal pattern of disease, with new cases appearing in late April through September and peaking in July. No new cases appear during late fall or the winter months. This pattern is suggestive of ________.

disease transmission by an arthropod vector such as a mosquito or tick

Fungi that produce only asexual spores are called __________.

anamorphic, anamorphs, anamorphic fungi

Diseases caused by fungi are called __________.

mycoses

The filaments of molds and fleshy fungi are referred to as __________.

hyphae, mycelium, mycelia

Merozoites, sporozoites, trophozoites, and gametocytes are part of the Plasmodium life cycle. In the __________ stage, malaria is transmitted to humans by the mosquito.

sporozoite, sporozoites

The __________ is the part of a tapeworm that attaches to the host.

scolex

An arthropod that transmits pathogenic microbes to a host is known as a/an __________.

vector

A protective structure formed by certain protozoa under adverse conditions is called a/an __________.

cyst

__________ are symbiotic fungi that help plant roots absorb water and minerals from the soil.

Mycorrhizae

Cestodes (tapeworms) have many segments known as __________ that contain reproductive structures.

proglottids

Trematodes are also known as __________.

flukes

Members of a fungal phylum are characterized by a specific type of sexual spore.

True

Most plants benefit from symbiotic fungal partners.

True

Because of their role as producers in the aquatic environment, algae are beneficial to all of the other organisms in the aquatic ecosystem.

False

All fungi produce both asexual spores and sexual spores.

False

Slime molds are in the Fungi kingdom.

False

The Apicomplexan protozoa, such as Plasmodium and Toxoplasma, use an apical complex structure to help penetrate the host cell.

True

Humans are intermediate hosts for Plasmodium spp.

True

All algae are either filamentous or unicellular.

False

The phylum Platyhelminthes contains the cestodes and trematodes.

True

Nematodes are always intestinal parasites.

False

What is meant by a "definitive" host?

A definitive host is one in which sexual reproduction of a microorganism takes place.

In the life cycle of the fluke Paragonimus, where does the miracidium fit?

Miracidium hatch from eggs and are eaten by snails.

The spores formed by Rhyzopus during sexual reproduction are

Haploid

Viruses possess genetic material comprised of ________.

DNA or RNA

Which of these processes of viral multiplication is most likely to damage the host cell?

release of nonenveloped viruses

Which of the following are possible strategies for treating viral infections?

all of the above: blocking viral attachment to host cell receptors, blocking uncoating of the virus after entry, blocking insertion of viral DNA into the host cell chromosomes, blocking biosynthesis of viral nucleic acids.

A double-stranded, enveloped DNA virus that contains reverse transcriptase belongs to which family?

Hepadnaviridae

Members of the Adenoviridae cause ________.

the common cold

Which method cannot be used to culture viruses in a laboratory?

nutrient agar culture media

Cell lines derived from transformed (cancerous) cells are called ________.

continuous cell lines

During the bacteriophage lysogenic cycle, ________.

phage DNA is inserted into the host chromosome

After the attachment and entry of a virus into a host cell, what is the next step in the multiplication of animal viruses?

uncoating

An example of a latent virus infection is ________.

shingles

A virus may contain any of any of the following except ________.

ribosomes

Viruses that use RNA as a template for transcribing DNA include ________.

Retroviridae

Prion diseases can be acquired in all of the following ways except by ________.

direct contact

Which of the following terms are not correctly matched?

Poxviridae; chickenpox

In polio virus replication, the function of the antisense (- strand) RNA is to ________.

serve as a template for the production of sense (+ strand) RNA

How could a virus pick up a human oncogene?

specialized transduction

All of the following are RNA viruses except ________.

hepatitis B virus

To what does the term viral species refer?

a group of viruses sharing the same genetic information and structure

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