Pathogenic bacteria are classified as _____________ for their growth temperature requirements.
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:
Through metabolism pathogens often produce acids that interfere with their own growth. ________ are added to media to control pH changes.
An organism that grows both in the presence and the absence of oxygen and uses oxygen when it is available is called a/an:
Which of the following types of media is designed to suppress the growth of unwanted bacteria and encourage the growth of desired microbes?
If a single bacterium replicated every 30 minutes, how many bacteria would be present in 2 hours?
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:
Shrinking of the cell's cytoplasm in response to osmotic loss of water is called __________.
The __________ is the most common technique used to obtain pure cultures of microbes. (3 words)
streak plate method
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.
In a/an __________, cells are added to melted agar and poured into a petri dish. (2 words)
A type of cell-to-cell communication that allows bacteria growing in biofilms to communicate and coordinate their activity is known as __________. (two words)
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.)
Aerotolerant organisms can grow in the presence of oxygen because their cell wall protects them from toxic products of oxygen.
When the spread plate technique is used to inoculate culture media, some colonies form within the agar.
Turbidity, or cloudiness, of cell cultures measured by spectrophotometry is useful in detecting small amounts of microbial contamination in liquids.
Cells growing in a rich medium will have a steeper log phase slope than will those growing in a nutrient-poor medium.
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.
Which of the following infectious agents challenges current sterilization strategies that have been accepted and in use for decades?
Some antimicrobial treatments kill microbes; some inhibit growth. Which term refers to an agent that inhibits bacterial growth?
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?
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.
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.
Packages of milk and coffee creamers may be stored without refrigeration if they have been sterilized by ________.
ultra-high-temperature (UHT) treatment
Some microbes are very resistant to antimicrobial chemicals. Which of the following would be the easiest to kill?
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?
All of the following are examples of microbial control using heavy metals except ________.
benzoyl peroxide used for acne treatment
The following may be listed on the ingredients of your favorite snack food. Which of these products is not antimicrobial?
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.
__________ is a common household disinfectant that has been used to disinfectant everything from dairies to drinking water.
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.
Oxidizing agents, such as hydrogen peroxide, are useful for irrigating deep wounds where released oxygen will inhibit the growth of __________.
anaerobic bacteria, anaerobes
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.
The presence of organic matter, such as blood or saliva, may impair the action of antimicrobial chemicals.
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.
Ethylene oxide gas is used to sterilize medical equipment that might be damaged by exposure to the heat of autoclaving.
UV radiation and x-ray radiation are similar in that they damage DNA and have a high penetrating power.
Iodine is one of the least effective antimicrobial chemicals, effective only against certain very sensitive strains of bacteria.
Soap is ineffective in killing bacteria. Therefore, hand washing is a rather ineffective measure in preventing disease transmission.
Ionizing radiation can be used to sterilize some foods such as spices, meat, and fruits and vegetables.
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?
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.
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.
A fungus that produces sporangiospores and zygospores and has hyphae without cross-walls would be classified in the category ________.
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 ________.
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
Merozoites, sporozoites, trophozoites, and gametocytes are part of the Plasmodium life cycle. In the __________ stage, malaria is transmitted to humans by the mosquito.
A protective structure formed by certain protozoa under adverse conditions is called a/an __________.
__________ are symbiotic fungi that help plant roots absorb water and minerals from the soil.
Cestodes (tapeworms) have many segments known as __________ that contain reproductive structures.
Because of their role as producers in the aquatic environment, algae are beneficial to all of the other organisms in the aquatic ecosystem.
The Apicomplexan protozoa, such as Plasmodium and Toxoplasma, use an apical complex structure to help penetrate the host cell.
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.
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?
After the attachment and entry of a virus into a host cell, what is the next step in the multiplication of animal viruses?
In polio virus replication, the function of the antisense (- strand) RNA is to ________.
serve as a template for the production of sense (+ strand) RNA
To what does the term viral species refer?
a group of viruses sharing the same genetic information and structure
Which of these enzymes is necessary for the replication of a + strand RNA virus?
RNA-dependent RNA polymerase
Which of these statements is not true?
Attachment of animal viruses to host cells is random and nonspecific.
The potential use of viruses that infect bacteria to treat bacterial infections in humans is known as __________. (2 words)
phage therapy, bacteriophage therapy
During the lysogenic cycle of the bacteriophage lambda, integrated phage DNA is known as the __________.
When viruses infect cell cultures, they often produce damage to the cells called __________. (2 words)
Retroviridae use an RNA-dependent DNA polymerase, called __________, to transcribe DNA from an RNA strand.
The toxin production by Corynebacterium diphtheriae carrying a temperate phage is an example of __________. (2 words)
During the maturation of enveloped viruses, the envelope is acquired through budding from the host cell membrane.
Viruses range from 20 to 1000 nm in length and are easily seen using a compound light microscope.
Of the following diseases, which one is caused by viruses that belong to the Papovaviridae family?
The uncoating of an animal virus by the host cell is equivalent to what step in the lytic cycle of bacteriophage?
Put the steps of the lytic cycle in the proper order:
attachment, penetration, biosynthesis, maturation, release
is capable of entering a lysogenic cycle. This happens when the circularized phage DNA is inserted into the host's chromosome. As the host DNA is replicated, so is the phage DNA. Occasionally a lysogenized bacterial cell will have the phage DNA "pop out," and a lytic cycle will result.