Microbiology FINAL
Which of the following are the standard conditions for an autoclave?
121 °C, 15 psi, 20 minutes
Antigenic shift caused a severe influenza pandemic, the "Spanish flu," during which years?
1918-1919
Match each bacterial disease with its distinguishing characteristics.
Acute otitis media A. very common in young children; may occur with or without fluid buildup Diphtheria B. associated with the production of an exotoxin that causes the formation of a pseudomembrane that impairs breathing Pertussis C. causes severe coughing that can last for months; especially dangerous for infants; can be effectively prevented through vaccination Streptococcal pharyngitis D. can be associated with serious sequelae, such as acute glomerulonephritis and rheumatic fever Tuberculosis E. associated with severe cough and small, round lesions in the lungs; antibiotic resistance is a serious problem
Match each type of organism with the best description of its oxygen requirements.
Aerotolerant anaerobes C. an organism that grows equally well with or without oxygen facultative anaerobe D. an organism that can grow without oxygen but that grows best with oxygen microaerophile E. an organism that requires a low concentration of oxygen (less than the oxygen concentration in the atmosphere) obligate aerobe A. an organism that requires oxygen to survive obligate anaerobe B. an organism that requires an oxygen-free environment
The skin is an effective barrier against many pathogens. All the following describe ways that pathogens penetrate the skin except for which one?
Bacteria on the surface of the skin often gradually consume the epidermis and dermis, creating a pathway to deeper parts of the body.
Why are Pseudomonas aeruginosa infections difficult to treat?
Because they form biofilms, which are difficult for antibiotics to penetrate
There has been considerable concern about finding good ways to treat infections involving biofilms, such as those that develop on medical devices. What characteristics of biofilms complicate the treatment of infections involving biofilms?
Biofilms contain certain pathogens that increase the antibiotic resistance. Biofilms also allows for the exchange of extrachromosomal DNA, which also leads to antibiotic resistance. The proposed hypotheses include at least three possibilities. First, microbes in biofilms may be less metabolically active and bacteria that are less metabolically active are generally affected less by medications. Second, the extracellular polymeric substances may inhibit the ability of medications and other chemicals to penetrate the biofilm to affect the deeper cells. In addition, microbes in biofilms may have metabolic abilities that help to counteract medications. For example, they may be able to pump out antibiotics using efflux pumps. Finally, microbes in biofilms can exchange resistance genes through horizontal gene transfer.
Trichomonas vaginalis consumes other microbes. What effect does this have?
By consuming the normal microbiota, it causes an imbalance that increases the risk of infection.
Match each pathogen with the best description (bacterial, fungal, protozoal, or viral).
Candida albicans A. fungal Chlamydia trachomatis B. bacterial HSV-2 C. viral Trichomonas vaginalis D. protozoal
Match each type of illness with the appropriate vaccine for its prevention.
Chicken pox A. varicella Diphtheria D. DtaP, TdaP, DT, Td, or DTP Epiglottitis B. Hib Rubella C. MMR vaccine Tuberculosis E. BCG
Match the different steps of molecular cloning to their function.
DNA ligase D. joins together sugar-phosphate backbone of DNA PCR C. amplifies gene of interest plasmid E. small circular DNA used for cloning restriction endonuclease B. cuts both DNA containing gene of interest and vector DNA X-gal A. chromogenic substrate used for blue/white screening
A simple example of controlling microbial growth is based on how we handle our food products. Name three food preparation methods that counter microbial growth. Be sure to discuss the mode of action for each method.
Disinfection- kills microorganisms by using heat or chemicals. Sanitation- this also kills microorganisms according to safe public health levels with the use of heat and/or chemicals. Degerming- reduces microorganisms on the skin by scrubbing hands or using mild chemicals. Heat. We cook our foods to certain temperatures to ensure that microbial growth is killed. Heat denatures proteins and disrupts membrane integrity.Smoking. Meats are smoked with moist heat. Moist heat can easily penetrate cells. Like heating, smoking would denature proteins and disrupt membrane integrity of microbes.Pickling. Pickling lowers the pH of food. Lowered pH inhibits enzyme activity in microbes.Drying. Meats are cooked and dried (i.e., beef jerky). The removal of water inhibits metabolic pathways in microbes.Salting. Similar to drying, salt removes water, inhibiting metabolic pathways in microbes.
Which of the following correctly explains why DNA replication is described as semiconservative?
Each daughter strand contains one old strand and one new strand.
Match each illness with the most appropriate definition.
Epiglottitis B. inflammation of the epiglottis Laryngitis D. inflammation of the larynx Otitis C. inflammation of the ear Rhinitis A. inflammation of the nasal cavities Sinusitis E. inflammation of the sinuses
Which describes one difference between prokaryotic and eukaryotic DNA replication?
Eukaryotes have more origins of replication than prokaryotes
ATP is produced through oxidative phosphorylation when which of the following occurs?
H+ moves through ATP synthase
Reverse transcriptase inhibitors, such as AZT, can be used to target which virus?
HIV
HPV is extremely common and can be associated with genital warts, vaginal cancer, vulvar cancer, penile cancer, and anal cancer. How can it be so common with many infected people not realizing they have been infected?
Infections are often asymptomatic and clear without treatment.
Which of the following correctly describes uracil and where is it found?
It is a nitrogenous base found in RNA only.
Which of the following correctly describes uracil and where it is found?
It is a nitrogenous base found in RNA only.
How does sebum affect microbial growth on the skin?
It may aid growth by providing nutrients but also has components that inhibit microbial growth.
Why is it helpful for some bacteria, such as Staphylococcus aureus, to produce virulence factors during the stationary phase of growth in a batch culture?
It starts the production of enzymes that break down human tissue and cellular debris, so that bacteria can spread to nutrient rich tissue. Cells enter the stationary phase because their environment has become less favorable for growth because of increased concentrations of waste products and/or reduced availability of nutrients and oxygen. By producing virulence factors, bacteria may increase their ability to spread to new locations. For example, S. aureus produces enzymes that help it break down tissues to more easily move to new locations.
What does it mean to say that HSV-1 is often latent?
It undergoes periods of inactivity when it resides in trigeminal nerve ganglia and does not cause symptoms.
Which of the following is true of the normal skin microbiota?
It varies depending on microenvironment and is an important part of the nonspecific immune system.
In most women, which is the most common acid-producing bacterial genus in the vagina?
Lactobacillus
Which of the following is the correct order of phases of growth in the growth curve of a batch culture?
Lag phase, log phase, stationary phase, death/decline phase
Blackheads differ from whiteheads because whiteheads are covered by skin, whereas blackheads are open to the air. What causes the dark coloration?
Lipids within the sebum react with air, resulting in chemical oxidation and the formation of the black color.
Which researchers provided evidence that DNA replication was semiconservative?
Matthew Meselson and Franklin Stahl
Discuss how antibiotic resistance affects treatment recommendations and what can be done to deal with resistance.
My answer: A lot of diseases and our bodies are resistant to antibiotics, so doctors must look for other ways to treat certain diseases. I think a great way to deal with this issue is to cut down on the amount of antibiotics being prescribed when they really are not necessary. Students should provide examples of how antibiotic recommendations have changed for some pathogens because of resistance. Additionally, students should mention the general concepts of the following recommendations for antibiotic use: completing courses of antibiotics and using multiple antibiotic agents when needed. One potential example would be the common co-occurrence of N. gonorrhoeae and C. trachomatis, meaning that both should be treated simultaneously. Another example is the increasing U. urealyticum resistance to tetracyclines, meaning that fluoroquinolones are increasingly used instead.
Common cold viruses can often be differentiated from influenza by which of the following?
absence of a high fever
Match each infection with the most likely treatment.
acne (moderate) C. erythromycin, clindamycin, and others erysipelas A. antibiotics, especially penicillin necrotizing fasciitis B. intravenous antibiotics, debridement, and sometimes amputation Pseudomonas aeruginosa wound infections D. polymyxin B, fluoroquinolones, gentamicin, and others
Match the agent to its mechanism of action:
alcohols B. denature proteins and disrupt membrane integrity gamma rays A. damage DNA molecules heavy metals C. bind to sulfur-containing amino acids to inhibit enzyme activity soaps D. physically remove a microbe from a surface
Within the respiratory tract, where are oxygen and carbon dioxide exchanged?
alveoli
Influenza transmission between adults is most effectively prevented by which of the following?
annual vaccination of adults
Which condition occurs when the normal vaginal microbiota is unbalanced but there is no inflammation?
bacterial vaginosis
Match each disease with the common causative agent.
bacterial vaginosis D. Gardnerella vaginalis cervical cancer A. HPV chancroid E. Haemophilus ducreyi syphilis B. Treponema pallidum yeast infection C. Candida albicans
Restriction enzymes (endonucleases) are produced by bacteria as a means of protection against which infectious agent?
bateriophages
Bacteria typically divide by:
binary fission
Many chemical preservatives, such as potassium sorbate, preserve food products in which of the following ways?
by altering the pH
Due to antibiotic resistance, which of the following is the preferred first treatment for gonorrhea?
cephalosporins
What would be the most effective method of reducing the risk of Legionnaire's disease transmission?
cleaning and maintaining air conditioning systems well
Match the process that contributes to prokaryotic genetic diversity with the best description:
conjugation B. DNA is transferred through a pilus. transduction D. DNA is transferred by a bacteriophage transformation A. DNA is picked up from the environment transposition C. DNA excises from one location and inserts in another.
Match the process that contributes to prokaryotic genetic diversity with the best description:
conjugation D. DNA is transferred through a pilus. transduction A. DNA is transferred by a bacteriophage transformation B. DNA is picked up from the environment transposition C. DNA excises from one location and inserts in another
If you grow two species of bacteria on mannitol salt agar to determine which can ferment mannitol, and you know both species can grow on the medium, which type of medium is the agar?
differential
Sulfa drugs (sulfonamides) inhibit which metabolic pathway?
dihydrofolic acid synthesis pathway
Which of the following is another name for generation time?
doubling time
Autoclaves are designed to kill which of the following heat-resistant microbes?
endospores
The reaction breaks down ATP into ADP and inorganic phosphate is classified as:
exergonic
Which sequences of eukaryotic genes code for proteins?
exons
Which best describes bacterial growth during the log phase of the growth curve?
exponential
Which type of microbes thrive in the Great Salt Lake.
extreme halophiles
Which range of the electromagnetic spectrum is considered photosynthetically active radiation?
from visible light to infrared
In the United States, which sexually transmitted infection is especially common in individuals between the ages of 15 and 24 years?
gonorrhea
Match each molecule with its role in prokaryotic DNA replication.
helicase A. breaks hydrogen bonds between bases to open the double helix ligase B. joins Okazaki fragments together primase E. synthesizes small pieces of RNA to start the synthesis of new DNA strands. single-strand binding proteins C. helps hold open the double helix by preventing hydrogen bonding between the separated strands of the replication bubble sliding clamp D. helps hold DNA polymerase III in the proper position
Match each molecule with its role in prokaryotic DNA replication.
helicase B. breaks hydrogen bonds between bases to open the double helix ligase C. joins Okazaki fragments together primase E. synthesizes small pieces of RNA to start the synthesis of new DNA strands. single-strand binding proteins A. helps hold open the double helix by preventing hydrogen bonding between the separated strands of the replication bubble sliding clamp D. helps hold DNA polymerase III in the proper position
Match each type of microbe with the best description:
hyperthermophile C. temperature range for growth: approximately 80-110 °C mesophile D. optimal temperature range for growth: approximately 20-40 °C psychrophile B. temperature range for growth: approximately 0-15 °C psychrotroph E. grows well bet grows well between 4 °C and 25 °C thermophile A. temperature range for growth: approximately 50-80 °C
DNA polymerase III adds DNA nucleotides in which of the following direction(s)?
in the 5′ to 3′ direction only
Individuals who wear contact lenses are at particular risk of developing which of the following?
keratitis
Triglycerides are broken down by which of the following?
lipases
Which method of microbial control does not rely on denaturing proteins and/or disrupting the integrity of the cell membrane?
lypholization
Liquid growth media that contain antibiotics should be sterilized using which method?
membrane filtration
The study of all the DNA of an entire microbial community is known as which of the following?
metagenomics
Which of the following is not an example of evidence used by John Snow to determine that cholera was being transmitted by water in London in the 1800s?
microscopic examination of water
Rhinitis is an inflammation of which component of the respiratory system?
nasal passages
Which of the following is the most common category of bacteria?
neutrophiles
Stop codons are also known as:
nonsense codons
Which of the following actions would be most clearly considered bacteriostatic rather than bactericidal?
placing a bacterial culture in the −80 °C freezer
Phenolic compounds can be found naturally in which group of organisms?
plants
From a clinical perspective, aseptic technique is carried out to do which of the following?
prevent contamination in living tissue
Genomics would not be an effective method to detect which type of pathogen?
prions
Which of the following is not a function of the urinary system?
producing urea
Which of the following are enzymes that break down proteins?
proteases
Food spoilage is often caused by which type of microbe?
psychotrophs
The noncoding, repetitive sequences at the end of eukaryotic chromosomes are called which of the following?
telomeres
What is the name of the area on an enzyme that a substrate binds to?
the active site
The top part of the skin, which is exposed to the environment, is called:
the epidermis
Which of the following is used to determine if a solution of disinfectant actively used in the clinical setting is contaminated?
the in-use test
The initial cells added to a batch culture are called which of the following?
the inoculum
Which of the following best describes culture density?
the number of cells per unit volume
The central dogma describes which of the following?
the steps of gene expression
You are in the process of cloning a gene of interest into pUC19 using blue/white screening. You complete your cloning and transform E. coli with your cloned plasmid. You plate your transformation on two media. One medium agar plate contains X-gal only. The second medium agar plate contains X-gal and ampicillin (an antibiotic), in the hope of using blue/white screening. You examine your plates and see a mixture of blue and white colonies. Which of the following colonies should be picked?
the white colonies that are resistant to ampicillin
The influenza vaccine is designed to contain which of the following:
two influenza A strains and one to two influenza B strains, based on a review of the most dominant influenza strains in February and September
Which of the following is the definition of genetic engineering?
The alteration of DNA in a cell
Explain how normal exposures to microbes relate to the "hygiene hypothesis." Provide examples of evidence. Make sure to explain how people are exposed to microbes in everyday life and through the normal human microbiota.
The hygiene hypothesis states that exposure to different microorganisms in early years helps to fight off illnesses and build our immune system. We come into contact with microbes on a daily basis, so eventually our body starts to build up an immunity over time. Our bodies also contains bacteria and fungi that are beneficial to our health. The hygiene hypothesis suggests that normal exposure to microbes throughout life reduces the risk of immune disorders. The textbook describes the comparison of immune disorders in less developed countries and industrialized countries, and suggests that the reduced exposure to microbes and antigens in the latter is associated with greater incidence of immune disorders. Additionally, families with more children have lower rates of hay fever than those with fewer children. This relationship may reflect rates of infection or differences in antigen exposure that may correlate with average family size. The role of the normal microbiota in this process is not explicitly discussed in this chapter, so students need to use their prior knowledge to speculate about its effects and may have answers such as the following. Humans have a normal microbiota that interacts with potential pathogens. For example, the normal microbiota may outcompete other microbes and can produce chemicals (such as bacteriocins) that inhibit their growth. Exposure to the normal microbiota, and its effects on exposure to other microbes, also could affect immune system function.
Which of the following is the definition of biotechnology?
The use of living systems to benefit humankind
Measles causes primarily which of the following?
a skin rash and associated symptoms
Mutations may be harmful but may also be beneficial or neutral. Explain some examples of neutral and beneficial mutations.
Some examples of beneficial mutations are HIV resistance , lactose tolerance, and trichromatic vision. Neutral mutations are blood type and eye color. Neutral mutations have no effect on fitness (i.e., the ability of an organism to reproduce). They are not harmful or helpful. If the mutation occurs in the third base of a codon, the amino acid may not be changed (a silent mutation). Even if a single amino acid is changed, the protein may still function in some cases. Additionally, mutations may occur in noncoding regions and be neutral. Beneficial mutations may give an organism a new ability, such as antibiotic resistance. The text describes how a mutation may help to protect against HIV in the Micro Connections box "A Beneficial Mutation." In this case, a mutation in the gene for a receptor causes an abnormal receptor to be produced and this interferes with the ability of HIV to bind to the cell.
Alexander Fleming first observed a mold (now known as Penicillium notatum) that was able to inhibit which organism?
Staphylococcus
Which of the following is not a product of the Krebs cycle?
Pyruvate
A patient in the hospital develops a serious infection after surgery. How could you distinguish between an infection caused by a Staphylococcus species and one caused by a Streptococcus species? If the infection is caused by a Staphylococcus species, then how could you determine whether it was caused by S. aureus or S. epidermidis?
My answer: Staphylococcus will show a negative catalase test. Streptococcus will show a gram-positive cocci that grow in chains and pairs, while straphylococcus grows in grape like clusters. In a mannitol salt agar, S. aureus produces yellow colonies with a yellow medium and S. epidermidis will have a red medium and red colonies. Species of Staphylococcus and Streptococcus can most easily be distinguished under the microscope because of differences in their morphologies. Staphylococcus forms distinctive grape-like clusters, whereas Streptococcus forms chains. The bacteria can also be cultured; Staphylococcus has a distinctive opaque white to cream coloration when grown on blood agar. A catalase test can be used because Staphylococcus is catalase positive, whereas Streptococcus is catalase negative. To distinguish between S. aureus and S. epidermidis, passive agglutination testing can be used, although this does not definitively identify the species): S. aureus is coagulase positive and S. epidermidis is coagulase negative. These bacteria can also be cultured on mannitol salt agar, which distinguishes coagulase-positive species that ferment mannitol from coagulase-negative species that do not. Because species in both genera are gram-positive cocci, Gram staining is not sufficient to distinguish them.
Lori has a very bad sore throat. She goes to the doctor and is told that it is not a bacterial infection. The doctor then prescribes an antibiotic for her to take. Should the doctor have given Lori this prescription? Why would the doctor give such a treatment? Lori gets well! A week goes by and then the sore throat comes back. This time the doctor suspects strep throat. A culture is taken and sent to the lab to confirm, using blood agar, that she has strep throat. The lab then performs a Kirby-Bauer disk diffusion assay using antibiotics A through D. The results are shown below: Based on the results shown above, which antibiotic worked best? Which if any antibiotic shows any antibiotic-resistant colonies. If there are any antibiotic-resistant bacteria, how could they have arisen? c. Lori takes the antibiotic as prescribed and a week later returns to the doctor. Apparently the concentration being used is not working. Should the doctor just give a higher concentration of antibiotic? What problems may arise from this action?
No the doctor should not have given her an antibiotic. The doctor might have given her these just because she came in and needed something to "fix" her. This is what people expect from doctors. It also makes money for the doctors, pharmacies, and drug companies. Antibiotic D worked best. Antibiotic A shows signs of antibiotic-resistant colonies. This could have happened because Lori could possibly be becoming immune to this antibiotic because she has taken it multiple times. No the doctor should not give her a higher concentration. If they do, Lori might become resistant to that antibiotic. Antibiotics target bacteria. In that sense, the doctor shouldn't have prescribed an antibiotic. The doctor may prescribe an antibiotic not to cure but to help prevent a bacterial infection that may result because of the lowered immunity of the sick person. This should not be done because it can lead to an increase in antibiotic resistance. Heath-care providers often feel pressured to prescribe antibiotics, so he or she may have felt that way.(i) D worked best. (ii) Several colonies were resistant to A. They could have arisen from spontaneous mutations, transposons, or the mechanisms of horizontal gene transfer (i.e., transformation, transduction, conjugation). c. Exposure to antibiotics provides selective pressure, which makes the surviving bacteria more likely to be resistant. Giving higher concentrations provides more selective pressure, potentially resulting in more resistant bacteria and higher MIC concentrations required to eradicate the infection.
Which of the following is not true of biofilms?
Nutrients are equally distributed throughout a biofilm, so all the cells are healthy and resistant.
During DNA replication, the lagging strand is formed from which of the following?
Okazaki fragments
Which microbe causes streptococcal pharyngitis (strep throat)?
S. pyogenes
