Microbiology Exam 4

Acidophilus Milk Yogurt Cheese

--A culture of L. acidophilus is added immediately before packaging. The microbes are included for a possible health benefit in the human intestinal tract. --Pasteurized milk is inoculated with Streptococcus thermophilus, then incubated at 40-45° C for several hours under controlled conditions to alter the milk's consistency and flavor. --Pasteurized milk is inoculated with Lactococcus cremoris and L. lactis, then incubated until fermentation products cause the milk proteins to coagulate.

Which factors made it possible to eradicate smallpox?

-An effective smallpox vaccine was developed -The disease had distinctive, identifiable symptoms -Humans are the only host for smallpox

Which of the following are practical/reasonable mechanisms for preventing spread of pathogens among patients and healthcare workers in hospitals?

-Providing protective equipment such as gloves and masks -Isolating at-risk patients -cleaning and disinfecting medical equipment

Identify the factors that result in streams and rivers generally being aerobic. -Rivers and streams flow rapidly and are turbulent, facilitating O2 circulation. -Rivers and streams can be shallow, allowing light to penetrate to the bottom and facilitating photosynthesis throughout the water body. -Rivers and streams lack heterotophs that consume dissolved O2. -The water in rivers and streams is very warm, and aerobes prefer warm temperatures. -Rivers and streams contain high levels of glucose that autotrophs use to produce O2 through photosynthesis.

1,2

Which of the following cause foodborne intoxications? --Staph. aureus --Shiga-toxin producing E.coli --Clostridium botulinum --Campylobacter species --Lactobacillus species --Salmonella species

1,2

Please select all of the foods and beverages from the list below that are produced by microbial fermentation. --Bread --Yogurt and cheese --Beer and wine --Pickles --Prunes and raisins

1,2,3,4

Which of the following are nitrogen-fixing genera? -Bradyrhizobium -Sinorhizobium -Frankia -Anabaena -Azolla -Azorhizobium

1,2,3,4,6

Identify what researchers can learn about a microbial community using metagenomics. -They can identify the genes that are present in a microbial community -Knowing what genes are present in a community may facilitate identification of microbes -they can determine which microbes can be cultivated in the laboratory -They may learn what role a particular microbe has in the environment -They may identify novel pollutants in the environment

1,2,4

Which of the following factors can influence the ability of an organism to compete successfully for a habitat? -The rate at which the organisms multiplies -The ability of the organisms to withstand adverse environmental conditions -The ability of the organism to attack and consume other microbes in the area -The ability of the organism to inhibit other microbes by producing antimicrobial compounds -The ability of the organism to cause disease in humans and animals in the environment

1,2,4

In a freshwater lake, what is the epilimnion that can form in summer months due to thermal stratification of the water?

An oxygen-rich layer near the surface that forms due to the activities of photosynthetic bacteria.

Please choose the equation that illustrates the production of alcoholic beverages.

Anaerobic reaction of Yeast + Sugar = Ethanol + Carbon Dioxide

Primary Producers Consumers Decomposers

Autotrophs that convert CO2 into organic materials; serve as a food source for other ecosystem members -heterotrophs that eat other organisms; several together can create a food chain, while multiple chains create a food web -Heterotrophs that digest the remains of the other two groups in ecosystems; specialize in digesting complex molecules such as cellulose

Please match the type of epidemic to its corresponding example to test your understanding of common-source and propagated epidemics.

Common source-- the persistent cholera epidemic studied by John Snow in London, during which he traced the source to a sewage-contaminated community pump Propagated epidemic-- An outbreak of chickenpox among unvaccinated children in a large Amish community

What is a common cause of wine spoilage?

Conversion of alcohol to vinegar by acetic acid bacteria naturally occurring on grapes.

Which of the following describes an analytical epidemiological study?

Designed to determine which potential risk factors are actually relevant in the spread of the disease. Can include cross-sectional, retrospective, and prospective studies.

The fresh or partially decomposed organic matter used as a food source by decomposers is known as

Detritus

Which of the following is LEAST likely to change the composition of an infant's normal microbiota?

Diaper Brand

Select the TRUE statements regarding oligotrophic lakes. -The water temperature varies, depending on season and depth. -The upper layer, called the epilimnion, is generally O2 rich due to the activities of photosynthetic organisms. -The upper layer, called the epilimnion, is generally O2 poor due to the activities of photosynthetic organisms. -The lower layer, the hypolimnion, may be anaerobic due to the consumption of O2 by heterotrophs. -The lower layer, the epilimnion, may be anaerobic due to the consumption of O2 by heterotrophs. -Between the epilimnion and the hypolimnion is the thermocline, a zone of temperature stability. -Between the epilimnion and the hypolimnion is the thermocline, a zone of rapid temperature change.

1,2,4,7

Select the ways in which microbes are identified and classified in the laboratory. -16S rRNA sequencing -18S rRNA sequencing -Sequencing entire microbial genome -Mitochondrial DNA sequencing -Deducing amino acid sequences in ribosomal proteins

1,2,5

Which microbial groups are most likely to spoil refrigerated foods? --Psyhrophiles --Thermophiles --Psychorotrophs --Hyperthermophiles --Any of these groups

1,3

Select the factors that play a role in microbial competition. -Ability to produce antimicrobial compounds -Ability to grow to a very large size -Ability to multiply faster than other microbes in the environment -Ability to withstand adverse environmental conditions -Ability to rapidly flee from other aggressive microbes

1,3,4

Please select all methods of food preservation from the list. --Drying --Ultraviolet irradiation --Lowering the pH --Salt and sugar --Pasteurization --Antibiotics

1,3,4,5

Which of the following are reasons that made smallpox virus a good target for eradication? 1. Human beings were the only reservoir for the virus 2. There was only a single animal reservoir for the virus 3. The symptoms of the disease were highly evident and obvious 4. An effective vaccine was able to be produced and administered across the globe 5. Administration of the live attenuated vaccine to the U.S. population only gradually led to immunization of the rest of the world as Americans traveled abroad 6. Obviously infected individuals were able to be quarantined quickly to prevent spread of infection to other susceptible individual's 7. Low levels of mortality induced by the disease gradually left most of the global population immune to rein infection. The virus burned itself out.

1,3,4,6

Select the TRUE statements regarding foodborne intoxications. --Result from ingesting an exotoxin secreted by a microbe growing in/on the food --Result from ingesting living microbes growing in/on a food product --May result after improper canning of certain foods --Can be avoided by vaccination --An example of a foodborne intoxication is botulism --Symptoms usually include diarrhea

1,3,5

1. Descriptive studies 2. Analytical studies 3. Experimental studies

1. Attempt to identify potential risk factors that lead to disease 2. Attempt to determine which risk factors are relevant to disease development 3. Used to evaluate the effectiveness of a treatment or intervention in preventing disease

1. Cranberries 2. Dried meat 3. Whole pecans

1. Natural antimicrobials 2. Low aw 3. Physical barrier

1. Metagenomics 2. Fluorescence in situ hybridization 3. DNA microarrays

1. Using microbial DNA sequence information to observe commonly conserved genes for particular traits 2. Using fluorescent probes to look for specific microbes in an area/community 3. Comparing microbial populations by studying gene expression

1. Sporadic diseases 2. Epidemic 3. endemic 4. Pandemic 5. Outbreak

2. An unusually large number of cases of a disease in a population 3. Diseases constantly present in a population 5. An epidemic that spreads over several continents 1. A disease that occurs only from time to time 5. Group of cases of a disease in a specific population

1.Cross-sectional study 2. Case-control study 3. Descriptive study 4. Cohort study 5. Experimental study

3. Data collected from an outbreak used to predict risk factors in spread of that disease 2. Comparison of diseases people with healthy controls to determine events leading to disease 1. Snapshot assessment of a particular population to determine associations between risk factors and disease 4. Groups of people with known risk factors followed over time to correlate disease cause with effect 5. Assessment of effectiveness of preventative factor by comparing cohorts receiving either treatment or placebo.

1. Bacillus species 2. Streptomyces species 3. Azospirillum species

3. Fix nitrogen 1. Form endospores 2. Produce antibiotics

1. Patient microbiota 2. Healthcare workers 3. healthcare environment 4. Other patients

4. A sneezing and coughing patient sharing a room with another patient 3. Drug-resistant Pseudomonas aeruginosa growing on a bar of soap used by a hospitalized but ambulatory patient to scrub his skin in a shower. 2. A physician with a mild case of undiagnosed influenza who reports to work. 1. Staphylococcus epidermidis on the patient's skin around the site of an IV catheter insertion.

1. Poultry, eggs, milk 2. Oysters 3.Raw milk and cheese 4. Rice, meat, vegetables 5. Low-acid canned foods

4. Bacillus cereus 5. Clostridium botulinum 2. Vibrio vulnificus 1. Salmonella species 3. Listeria monocytogenes

1. Acetobacter species 2. Leuconostoc species 3. Erwinia species 4. Bacillus species 5. Alcaligenes species 6. Pseudomonas species

6. Degrade a wide variety of different compounds so spoil many foods 3. Produce enzymes that degrade pectin, spoiling fruits and vegetables 1. Transform ethanol into acetic acid, spoiling wine 5. Form a glycocalyx that spoils milk 2. Produce lactic acid that spoils milk 4. Spoil canned goods and may cause illness

Consider the graphs. Which of the factors does NOT explain why the proportion of deaths due to cancer and heart disease in the United States today is much higher than it was in 1900.

Reduced incidence of an infectious disease due to an aging global population.

Which of the following is NOT one of the molecular Koch's postulates?

Replacement of the mutated virulence gene with a wild-type gene should have no impact on the virulence of the strain.

Some people consider Staphylococcus aureus to be a primary pathogen, while others classify it as an opportunist. Which of the following statements supports the opinion that it is an opportunist?

S. aureus is found in the nasal passages of many healthy people.

Which of the following statements describes how antibodies can cause damage to host tissue during a bacterial infection?

The bacteria have molecules similar enough to our molecules that cross-reactive antibodies are produced which target host tissues.

Please read the following scenario: "Molly developed gastroenteritis after eating raw cookie dough. Upon culture of her stool, the causative agent was shown to be Salmonella enterica serotype Typhimurium. Presumably the Salmonella was in the uncooked eggs in the raw cookie dough." What is the reservoir for the infection in this case?

The chickens from which the eggs came

Select the TRUE statement regarding the microbial competition figure.

The cocci are replicating faster than the rods.

A typhoid fever (bacterial disease) outbreak that originated at a ski resort in Switzerland eventually resulted in more than 430 cases of the disease appeared in at least six countries. Which is the most likely reason for this outcome?

The disease has a long incubation period, so infected people had flown home before becoming ill, spreading it in their own countries.

Please select the FALSE statement regarding mycorrhizas.

They grow as endosymbionts within specialized organs called nodules.

During the production of soy sauce, the initial several days-long step is necessary in order to

allow for production of fermentable sugars, peptides, and amino acids that the salt-tolerant microbes involved in the process can ferment to produce soy sauce.

Spoiled foods are

any foods that have undergone an undesirable change due to microbial growth.

Babies born by cesarean section are likely to have less Lactobacillus species in their normal microbiota than babies born vaginally.

True

Bacteria that reside within a host cells can avoid the bactericidal effects of the complement cascade

True

Global warming may increase the risk of emerging diseases because vectors are spreading to new environments.

True

Nitrogen fixation and ammonification are two different reactions in the nitrogen cycle that yield ammonium as a product.

True

Some people are genetically immune to diseases such as HIV/AIDS and malaria.

True

Some viruses are capable of regulating apoptosis, inhibiting the interferon response and interfering with antigen presentation.

True

The metabolism of lactic acid bacteria differs from that of most other microorganisms that can grow aerobically in that wost organisms that grow aerobically use aerobic respiration, lactic acid bacteria only ferment.

True

The sulfur cycle resembles the carbon cycle more than the nitrogen cycle in that sulfur is mostly in solid form and originates from natural sedimentary deposits rather than from the atmosphere.

True

The use of starter cultures improves the safety of fermented meat products by increasing the number of microbes that create acidic end products, thereby inhibiting the pathogens that otherwise might grow.

True

M cells in the intestinal epithelium are important because pathogenic bacteria such as Shigella species

Use them to gain access to underlying tissue

Which of the following immune responses is best suited to prevent a virus from infecting a cell?

Virus-specific antibodies

Which of the following would typically be the most numerous in soil?

Gram-positive bacteria

Following an outbreak of a diarrheal illness in school children, which would be the best group to use as a control in a case-control study?

Healthy classmates of the children with diarrhea.

Which of the following statements indicates the significance of Koch's work?

His postulates are used to show that specific microorganisms can cause specific diseases

Under what circumstance could the number of cases from a common-source outbreak remain high over a much longer period of time and not decrease to zero?

If the source continued to infect new people e.g. if a restaurant continues to serve contaminated food.

Consider the figure of a lichen. In this symbiotic relationship, the photosynthetic alga provides the fungus with organic nutrients. The fungus provides the alga with water and protection. Which of the normal microbiota relationships described below is most similar to this association?

Mutualism - intestinal bacteria providing host with vitamins E and K.

The growth and metabolism of organisms themselves can alter an environment dramatically. Why?

Nutrients may become depleted, and a variety of potentially toxic waste products may accumulate.

Which of the following statements about pathogenesis is FALSE?

Pathogens that destroy complement component C3b can avoid the classical pathway of activation.

In areas with no sunlight, ______ obtain energy by oxidizing hydrogen sulfide and fix CO2, providing animals in the area with both a carbon and an energy source.

chemolithoautotrophs

Toxins that are not components of the bacterial cell structure are called ______.

exotoxins

Most bacteria require an aw (water activity) above 0.90 for growth. Which of the following is likely to spoil quickest?

fresh stew - aw 0.98

Consider the figure of a virus infected cell. By directing the host cell to synthesize fake MHC class I molecules, the virus is

making sure its host is not destroyed by TC cells or NK cells.

A new disease spreads rapidly around the world, causing disease in many but death in few. From this information, you can reasonably state that this

pandemic has a high morbidity rate.

Production of vinegar from alcohol is carried out by oxidation via

the acetic acid bacteria—Acetobacter and Gluconobacter species.

The tart taste of yogurt, pickles, sharp cheeses, and some sausages is due to

the production of lactic acid as a by-product of fermentation in these foods by bacteria.

Bacteriocins are ______ produced by bacteria that kill off closely related strains, thereby reducing competition in a low-nutrient area.

toxins

What is a zoonosis

A disease of animals (other than humans) that can be transmitted to humans.

Consider the statements below. Which of the people described is LEAST likely to contract the disease?

A person who contracts 30 cells of a pathogen that has an infectious dose of 100,000 cells.

Which of the following statements about the composition of an infant's normal microbiota is FALSE?

All newborn babies have the same normal microbiota composition.

Which of the following refers to a descriptive epidemiological study?

Collecting data that characterize the occurrence, from the time and place of the outbreak to the individuals infected.

A microbial mat is a thick, dense, highly organized structure composed of distinct layers. They are examples of a specific type of ______.

Biofilm

How does boiling a home-canned food immediately before serving it prevent botulism?

Botulinum toxin is denatured by heat, becoming harmless.

Why is the temperature of the canning process for acidic fruits and pickles not as high as that required for canning beans?

C. botulinum does not grow or produce toxin below pH 4.5, so it is not a danger in highly acidic foods.

Please choose the best definition of virulence factors.

Characteristics of a microorganism that enable it to establish infection and cause disease.

Primary producers can be either photoautotrophs (using sunlight for energy) or chemolithotrophs (oxidizing ______ chemicals for energy).

Chemolithotrophs

Which foodborne pathogen can cause hemolytic uremic syndrome?

E. coli O157:H7

Please select the mode of disease transmission being demonstrated in this scenario: A teacher walking through her first grade classroom pauses to pick up a used tissue that ended up on the floor instead of in the waste basket. Unfortunately, after discarding the tissue, she doesn't immediately wash her hands, and acquires a strain of rhinovirus. Several days later she begins to experience the symptoms of a cold.

Fomite

It is normal for the meninges to become inflamed during an infection and no additional concern is warranted.

False

Why is an orange more likely to be spoiled by fungi than by bacteria?

Fruits are naturally more acidic than bacteria can tolerate, allowing acid-resistant fungi to grow without competition.

What would happen if a pathogen lost the ability to make adhesins?

It would be unable to attach to and colonize a host.

Which molecule is responsible for displaying fragments of proteins made within the cell and would therefore be useful in detecting a virally infected cell?

MHC

Which of the following diseases can potentially be eradicated and why? Select all the correct answers.

Measles, because there is an effective vaccine (MMRV) Polio, because there are effective vaccines

Which of the following is a mechanism used by pathogens for avoiding antibodies?

Molecular mimicry

Which of the following pairs about protozoan and helminth pathogenesis is mismatched

Plasmodium vivax—attaches to Duffy antigen on white blood cells.

Much work is currently being done toward global eradication of which of the following diseases?

Polio

Please choose the correct statement that describes the actions of methanogens in the carbon cycle.

Produce methane in anaerobic ecosystems

Which of the following does NOT help a pathogen establish an infection?

Producing a capsule that prevents deposition of complement C3b.

In which way does cytomegalovirus avoid the cellular immune response?

Producing fake MHC class I molecules that NK and Tc cells do not recognize

Which of the following is NOT a method used by pathogens for penetrating skin or mucous membranes?

Production of endotoxin

Please select the pair that is incorrectly matched, regarding establishing an infection.

Siderophores - injecting toxins

Which of the following is considered the most difficult barrier for microbes to penetrate?

Skin

Which of the following is NOT an intrinsic factor influencing the growth of microbes in food?

Storage temperature

Which of the following is NOT a potential reservoir of infectious agents in healthcare settings?

These are all potential reservoirs of infection