Question 1

Transformation is the transfer of DNA from a donor to a recipient cell?

Accepted Answer

Answer reason: Transformation is a form of horizontal gene transfer in which competent bacteria take up free extracellular DNA from their environment and incorporate it into their genome or maintain it as a plasmid. This specifically describes uptake of “naked” DNA without requiring a viral vector or direct cell contact. Transfer mediated by a bacteriophage is transduction, and transfer requiring cell-to-cell contact is conjugation. Crossing over and sexual reproduction are eukaryotic genetic mechanisms and are not the defining process for bacterial transformation.

Question 2

Repair of damaged DNA, in some instances and mechanisms, might be viewed as a race between an endonuclease and?

Accepted Answer

Answer reason: DNA repair pathways commonly remove damaged or mismatched nucleotides via endonuclease cleavage, creating a gap that must be rapidly filled to restore DNA integrity. The competing step is resynthesis of the correct DNA sequence using the intact strand as a template, which is performed by the replicative/repair DNA polymerase. If gap filling is delayed, exposed single-stranded regions and nicks are more susceptible to further nuclease processing and strand break propagation, increasing genomic instability. Ligase primarily seals the final nick after synthesis, whereas helicase, methylase, and primase are not the key enzymes responsible for replacing excised bases in most repair mechanisms.

Question 3

Salts and sugars work to preserve foods by creating a?

Accepted Answer

Answer reason: High concentrations of salt or sugar increase the solute concentration outside microbial cells, creating a hypertonic environment. Water then moves out of the microorganism by osmosis, causing plasmolysis and inhibiting cellular metabolism and replication. This lowers water activity (aw), which is a key requirement for microbial growth in foods. A hypotonic environment would drive water into cells and would not inhibit growth, and lowering pH is a separate preservation mechanism (e.g., pickling/fermentation) rather than the primary effect of salting/sugaring.

Question 4

Which group of microorganisms is most likely to spoil a freshwater trout preserved with salt?

Accepted Answer

Answer reason: Facultative halophiles can grow without salt but also survive and proliferate when salt is present, making them common spoilers of salted fish and meats. Temperature-based groups like thermophiles and hyperthermophiles are adapted to hot environments and are unlikely to dominate spoilage of preserved fish stored at typical cool/ambient conditions. Anaerobes are defined by oxygen requirements rather than salt tolerance, so salt preservation does not specifically select for them.

Question 5

A bacterial culture grown in a glucose-peptide medium causes the pH to increase. The bacteria are most likely?

Accepted Answer

Answer reason: An increase in pH indicates alkalinization of the medium, which commonly occurs when bacteria metabolize amino acids/peptides and release basic byproducts such as ammonia via deamination. In a glucose-peptide medium, carbohydrate fermentation or oxidation typically generates acidic end products that lower pH rather than raise it. Therefore, a rising pH most strongly supports preferential utilization of peptides/proteins as the energy source. “Not growing” would not be expected to produce a consistent pH rise because minimal metabolism would occur.

Question 6

What is the fate of pyruvic acid in an organism that uses aerobic respiration?

Accepted Answer

Answer reason: In aerobic respiration, pyruvate is converted to acetyl-CoA by pyruvate dehydrogenase, and the acetyl group enters the citric acid (Krebs) cycle. The defining “fate” of pyruvate’s carbon skeleton under aerobic conditions is entry into this cycle, where acetyl-CoA condenses with oxaloacetate to initiate the pathway by forming citrate. In contrast, reduction to lactic acid is an anaerobic fermentation pathway used to regenerate NAD+ when oxygen is not available. The electron transport chain oxidizes NADH and FADH2 (not pyruvate directly), and glycolysis is the pathway that produces pyruvate rather than consumes it.

Question 7

Gallionella bacteria can get energy from the reaction Fe2+ → Fe3+. This reaction is an example of?

Accepted Answer

Answer reason: Oxidation is defined as loss of electrons and typically corresponds to an increase in oxidation state/positive charge. In the reaction Fe2+ → Fe3+, iron goes from +2 to +3, meaning it has lost one electron, which is an oxidative step that can be coupled to energy conservation in chemolithotrophic bacteria. Reduction would instead be Fe3+ → Fe2+ (gain of an electron). Fermentation, photophosphorylation, and the Calvin-Benson cycle involve distinct metabolic pathways that do not describe this direct electron-loss redox change.

Question 8

Which organism is NOT correctly matched to its energy source?

Accepted Answer

Answer reason: Photoautotrophs use light as their energy source and typically use CO2 as their carbon source, so pairing them with CO2 as an energy source is incorrect. In contrast, photoheterotrophs do use light for energy (but require organic carbon), and chemoheterotrophs can use glucose as a chemical energy source. Chemoautotrophs can obtain energy by oxidizing inorganic chemicals such as Fe2+ or NH3, making those pairings reasonable.

Question 9

Which microscope is used to see intracellular detail in a living cell?

Accepted Answer

Answer reason: Two-photon excitation uses near‑infrared light and confines excitation to the focal point, reducing out-of-focus bleaching and allowing imaging deeper into live tissue with better preservation of cell viability. A transmission electron microscope cannot be used for living cells because it requires a vacuum and extensive fixation/sectioning, which kills cells. Standard brightfield microscopy generally lacks the contrast and resolution to reliably show many intracellular details without specialized techniques.

Question 10

The purpose of the ocular lens is to?

Accepted Answer

Answer reason: In a compound light microscope, the objective lens creates the primary magnified real image of the specimen, and the ocular (eyepiece) lens further magnifies that image for viewing. This is why total magnification equals objective magnification multiplied by ocular magnification. Resolution is primarily determined by numerical aperture and wavelength (with oil immersion and condenser alignment playing key roles), not by the eyepiece’s main function. Light intensity is controlled by the illuminator and iris diaphragm/condenser rather than the ocular lens.

Question 11

Which of the following pairs is mismatched?

Accepted Answer

Answer reason: Basic (cationic) dyes, in contrast, are attracted to the negatively charged cell envelope and therefore stain the organisms directly (a simple/positive stain approach). This makes pairing a basic dye with a negative stain conceptually incorrect. By comparison, nigrosin is a classic acidic dye used for negative staining, which fits the expected technique-dye relationship.

Question 12

Which of the following pairs is mismatched?

Accepted Answer

Answer reason: Safranin is the basic counterstain in the Gram stain, so pairing it with an acid dye is incorrect. Alcohol-acetone is correctly used as the Gram decolorizer, and iodine correctly functions as the mordant that forms a crystal violet–iodine complex. Carbolfuchsin is also a basic dye used in acid-fast staining, making that pairing appropriate.

Question 13

Which microscope is used to see internal structures of cells in a natural state?

Accepted Answer

Answer reason: This allows visualization of internal cell structures in a more natural, near-live state without fixation and staining that can distort morphology. A standard compound light microscope typically requires staining to clearly see many internal details. Electron microscopy provides very high resolution but requires extensive specimen preparation and a vacuum, so it does not show cells in their natural living state.

Question 14

Simple staining is often necessary to improve contrast in which microscope?

Accepted Answer

Answer reason: Simple stains add pigment to the organism, increasing contrast against the bright background and making morphology easier to visualize. Phase-contrast and darkfield techniques are designed specifically to enhance contrast in unstained, living specimens by optical principles, reducing the need for simple staining. Fluorescence microscopy instead relies on fluorochromes and specific excitation/emission, and electron microscopy uses electron-dense stains and different imaging physics rather than routine simple staining.

Question 15

Which microscope achieves the highest magnification and greatest resolution?

Accepted Answer

Answer reason: Electron microscopes use an electron beam with a much shorter effective wavelength than visible light, producing far greater resolving power and enabling much higher useful magnification. In contrast, compound light, phase-contrast, darkfield, and fluorescence microscopes are all light-based systems and remain constrained by the diffraction limit of visible light, even if they improve contrast for specific specimens. Therefore, among the listed instruments, the one that achieves the highest magnification and greatest resolution is the electron-based system.

Question 16

Which type of stain is most useful in helping clinicians to decide which antibiotic to prescribe for a bacterial infection?

Accepted Answer

Answer reason: This stain rapidly differentiates organisms based on peptidoglycan thickness and presence of an outer membrane, offering immediate empiric-therapy direction while cultures/susceptibilities are pending. It is routinely used clinically as a first-line classification test from specimens (e.g., sputum, CSF) to narrow likely pathogens and antibiotic coverage. In contrast, simple or negative stains mainly aid visualization and morphology, and endospore/flagella stains are specialized structural stains that do not broadly guide initial antibiotic choice.

Question 17

Which one of the following is most resistant to chemical biocides?

Accepted Answer

Answer reason: Protozoan cysts have thick, resilient walls and a metabolically quiescent state, making them harder for many disinfectants to inactivate than vegetative bacteria or enveloped viruses. Enveloped viruses are among the least resistant because disruption of the lipid envelope readily inactivates them. Mycobacteria are relatively resistant due to mycolic acids, but cyst walls typically provide an even more robust barrier in routine disinfection comparisons.

Question 18

The preservation of beef jerky from microbial growth relies on which method of microbial control?

Accepted Answer

Answer reason: Beef jerky is preserved primarily by drying, which removes moisture and creates an environment that inhibits enzymatic function and cellular metabolism. This is the classic principle of food preservation by dehydration rather than by physically removing microbes (filtration) or killing them with radiation. Lyophilization is freeze-drying used for items like vaccines or some foods, but jerky production relies on straightforward dehydration.

Question 19

Which of the following could be used to sterilize plastic Petri plates in a plastic wrapper?

Accepted Answer

Answer reason: Ionizing radiation (gamma rays) has strong penetration and reliably sterilizes prepackaged medical and laboratory plastics by damaging microbial DNA. An autoclave would melt/warp many plastics and cannot be used for items already sealed in typical plastic wrap. UV light and sunlight have poor penetration and are mainly surface disinfectants, so organisms shielded by the wrapper or in crevices would survive.

Question 20

Which of the following pairs is mismatched?

Accepted Answer

Answer reason: Ticks transmit Rocky Mountain spotted fever (Rickettsia rickettsii) and Lyme disease (Borrelia burgdorferi), and mosquitoes transmit malaria (Plasmodium) and several encephalitis-causing arboviruses, making those pairings appropriate. Pneumocystis jirovecii causes pneumonia via airborne person-to-person transmission, classically in immunocompromised patients, not via mosquitoes. Therefore this pairing is the mismatch.

Question 21

You see acid-fast oocysts in a fecal sample from a patient who has diarrhea. What is the MOST likely cause?

Accepted Answer

Answer reason: Cryptosporidium produces small, thick-walled oocysts that stain acid-fast and are shed in feces, making this finding highly specific in routine microbiology testing. Giardia typically presents with greasy, foul-smelling stools and is identified by cysts/trophozoites on O&P rather than acid-fast oocysts. Entamoeba is associated with flask-shaped ulcers and can cause dysentery, but it is not identified by acid-fast oocysts; Taenia is a cestode identified by eggs/proglottids, not oocysts.

Question 22

Which of the following is the most effective control for malaria?

Accepted Answer

Answer reason: Vector control (reducing Anopheles populations and preventing bites) directly targets the essential mosquito stage of the parasite life cycle, lowering community-wide incidence. Treating patients reduces morbidity and can decrease the human reservoir, but it is less effective as a population control measure when reinfection from ongoing mosquito transmission continues. “Eliminate the intermediate host” is incorrect framing for malaria because the mosquito is the definitive host (sexual reproduction occurs there), so the most practical and targeted control remains eliminating the vector.

Question 23

In the microscope, you observe multinucleated amoeboid cells with sporangia that form spores. This is a(n)?

Accepted Answer

Answer reason: A key distinguishing feature of plasmodial slime molds is a multinucleated, amoeboid mass (plasmodium) produced by nuclear division without cytokinesis. These organisms can develop sporangia that generate spores as part of their life cycle. In contrast, cellular slime molds primarily exist as individual haploid amoebae that aggregate into a multicellular “slug” rather than forming a single multinucleated cell. The other options do not match this morphology: ascomycetes are true fungi with asci, Euglenozoa are flagellated protists, and tapeworms are multicellular helminths.

Question 24

You observe a mass of amoeba-like cells that swarm together, form a stalk, and produce spores. This is a(n)?

Accepted Answer

Answer reason: Cellular slime molds exist as individual amoeboid cells that aggregate when nutrients are scarce, then differentiate into a multicellular “slug” and fruiting body (stalk) that releases spores. The key discriminator is the swarming/aggregation behavior leading to a stalked sporangium. Plasmodial slime molds instead form a single large multinucleate plasmodium rather than aggregating separate cells. Ascomycetes are true fungi with hyphae and asci, while Euglenozoa and tapeworms do not form stalked spore-producing structures.

Question 25

Molecular biology includes the study of?

Accepted Answer

Answer reason: Molecular biology focuses on how genetic material is stored, expressed, and regulated at the molecular level (the “central dogma”: DNA → RNA → protein). This includes transcription, translation, and the control of gene expression that determines which proteins a cell produces. The correct choice captures this integrative concept by linking genetic information to the downstream production of proteins. Individual processes like DNA synthesis or general enzyme function are components studied within biology, but they are narrower and do not define the core scope of molecular biology as directly as gene-to-protein information flow.

Question 26

Classification of organisms into three domains is based on?

Accepted Answer

Answer reason: The three-domain system (Bacteria, Archaea, Eukarya) is grounded in molecular comparisons that reflect evolutionary relationships, especially sequences of conserved cellular molecules. Differences in key cellular proteins (and the genes encoding them), alongside ribosomal RNA data, distinguish these domains more reliably than gross traits. Cell wall presence and nutritional needs vary widely within and across domains and are therefore poor primary criteria. Similarly, number of cells and general organization do not capture the deep genetic divergence that the domain level is intended to represent.

Question 27

Archaea differ from bacteria in that archaea?

Accepted Answer

Answer reason: A key distinguishing feature is that archaeal cell envelopes lack peptidoglycan and can be made of pseudopeptidoglycan, protein S-layers, or other polymers, whereas bacteria characteristically have peptidoglycan-based cell walls. This structural difference underpins major differences in susceptibility to agents like lysozyme and many beta-lactam antibiotics. The other options describe traits shared by both groups: both are prokaryotic, lack nuclei, and commonly reproduce by binary fission. Nutritional strategy is also not a defining split because both archaea and bacteria can be autotrophic or heterotrophic depending on species.

Question 28

Development of emerging infectious disease can be a result of all of the following EXCEPT?

Accepted Answer

Answer reason: Emerging infectious diseases are primarily driven by factors that increase pathogen evolution, introduction into new populations, or opportunities for transmission. Microbial mutation directly enables new virulence traits or antimicrobial resistance, allowing novel or more successful infections to appear. Modern transportation accelerates geographic spread and mixing of hosts, facilitating outbreaks from newly introduced pathogens. Environmental changes (e.g., climate shifts, habitat disruption) alter reservoirs and vectors, increasing human exposure, whereas genetically modified foods are not a recognized core driver of infectious disease emergence.

Question 29

Which of the following is NOT a characteristic of Neisseria?

Accepted Answer

Answer reason: Clinically important species (e.g., those causing gonorrhea and meningitis) are well-established human pathogens, so those traits fit the genus. The requirement for X (hemin) and V (NAD) growth factors is a hallmark of Haemophilus influenzae on chocolate agar, not Neisseria. Therefore, the growth-factor requirement is the mismatched characteristic.

Question 30

Rickettsias differ from chlamydias in that rickettsias?

Accepted Answer

Answer reason: Rickettsiae are obligate intracellular, gram-negative bacteria that are typically transmitted to humans via arthropod vectors such as ticks, mites, fleas, or lice. This vector-borne transmission is a key distinguishing feature from Chlamydia species, which spread mainly through direct contact (e.g., sexual, perinatal) or respiratory droplets depending on the species. Both organisms share intracellular dependence, so that feature does not differentiate them. Formation of elementary bodies is characteristic of chlamydiae, not rickettsiae.

Question 31

All of the following bacteria are gram-positive. Which does NOT belong with the others?

Accepted Answer

Answer reason: This option is acid-fast due to a mycolic-acid–rich cell wall, so it does not reliably Gram-stain as typical gram-positive bacteria. The other listed genera are classically gram-positive organisms that stain and group with gram-positive cell wall characteristics in routine classification. A common test-taking distinction is that acid-fastness is a separate staining category that supersedes Gram classification in practical lab identification.

Question 32

Thiobacillus oxidizes inorganic sulfur compounds and reduces CO2. This bacterium is a?

Accepted Answer

Answer reason: Oxidation of inorganic sulfur compounds indicates the organism obtains energy from chemical reactions involving inorganic molecules (chemo- and litho- energy source). Reduction/fixation of CO2 indicates carbon is sourced from CO2 rather than organic compounds, which defines an autotroph. Combining these traits yields a chemoautotroph. Phototroph options are incorrect because light is not the energy source described, and chemoheterotroph is incorrect because it would require organic carbon. The taxonomic label listed does not answer the metabolic classification being tested here.

Question 33

The nonsulfur photosynthetic bacteria use organic compounds as?

Accepted Answer

Answer reason: Anoxygenic photosynthetic nonsulfur bacteria perform photosynthesis without producing oxygen and typically use reduced organic compounds (or sometimes H2) as the reducing power source rather than water. These organic molecules donate electrons that drive the reduction of CO2 during carbon fixation. In contrast, oxygenic photosynthesizers use water as the electron donor, which is why oxygen is not an appropriate “source” here. Electron acceptors are not what these organisms are primarily described as needing from organic compounds in this context.

Question 34

Salmonella, Shigella, Yersinia, and Serratia are all?

Accepted Answer

Answer reason: These organisms are members of Enterobacterales, which are classically gram-negative bacilli that can grow with or without oxygen using fermentation and/or anaerobic respiration. Salmonella, Shigella, Yersinia, and Serratia all fit the shared morphology (rods) and staining pattern (gram-negative) that is commonly tested as a group-level trait. The distractor describing gram-positive aerobic cocci refers to an entirely different bacterial group (e.g., staphylococci/streptococci) with different cell wall structure and morphology. Endospore formation is a feature of certain gram-positive rods (e.g., Bacillus, Clostridium), not these enteric gram-negative bacilli.

Question 35

Which of the following bacteria are responsible for more infections and more different kinds of infections?

Accepted Answer

Answer reason: This genus commonly colonizes the nares and skin and is a leading cause of skin/soft-tissue infections, wound infections, bacteremia, endocarditis, osteomyelitis, and toxin-mediated syndromes, giving it both high frequency and wide clinical spectrum. Its ability to form biofilms on devices and its resistance patterns (e.g., MRSA) further increase the range and burden of disease. By contrast, several other listed genera are more classically associated with narrower syndromes (e.g., enteric illness or specific mucosal infections) despite being clinically important.

Question 36

Which aerobic gram-negative bacillus is the most common pathogen for all manifestations of urinary tract infection in all groups of clients?

Accepted Answer

Answer reason: Most uncomplicated and many complicated UTIs are caused by enteric gram-negative bacilli that colonize the periurethral area and ascend into the bladder. This organism is the predominant uropathogen across ages and sexes because it commonly originates from GI flora and has adhesins (fimbriae) that promote attachment to uroepithelium. Klebsiella and Pseudomonas are important causes but are more associated with healthcare exposure, catheters, or structural abnormalities and are less common overall. The remaining option is not a gram-negative bacillus and therefore does not match the organism type specified in the question.

Question 37

Which microscope is used to see detail of a 300-nm virus?

Accepted Answer

Answer reason: A 300-nm virus is near/beyond the effective limit for seeing meaningful detail with light-based modalities, even if it might be barely detectable as a blur. Electron microscopy uses electrons with much shorter wavelengths, providing nanometer-scale resolution needed to visualize viral morphology and fine structural details. The other listed light microscopy techniques mainly improve contrast for transparent specimens but do not overcome the fundamental resolution limit sufficiently for viral detail.

Question 38

All of the following are effective for destroying prions EXCEPT?

Accepted Answer

Answer reason: Prions are abnormally folded proteins that are highly resistant to routine physical and chemical disinfection methods. Simple boiling does not reliably denature or inactivate prions, which is why standard sterilization practices are insufficient for prion-contaminated instruments. Effective prion decontamination typically requires harsh approaches such as sodium hydroxide treatment combined with high-temperature extended autoclaving, or destruction by incineration. Because prions are proteinaceous, enzymatic digestion with strong proteases can reduce infectivity under appropriate conditions, making it a more plausible inactivation strategy than boiling.

Question 39

A client has recently been diagnosed with tuberculosis (TB). The nurse caring for the client anticipates that the client will develop?

Accepted Answer

Answer reason: TB infection elicits a delayed-type (type IV) hypersensitivity response mediated by T cells, which is what the tuberculin skin test (PPD/Mantoux) measures. A positive test is therefore an expected finding in someone with TB infection (or prior exposure/BCG), whereas timing predictions like “active TB within 2 weeks” or “within 1 month” are not reliable because progression from latent infection to active disease is variable and often occurs months to years later. Fever can occur with active TB, but it does not inherently imply severity requiring hospitalization and is not the most predictable development. The option that best reflects a consistent immunologic consequence of TB exposure/infection is the skin test conversion.

Question 40

A child is admitted to the hospital with flulike symptoms. Diagnostic testing reveals the IgM antibody parvovirus B19 is present. The nurse interprets this finding as being indicative of which condition?

Accepted Answer

Answer reason: A positive IgM indicates a recent/acute infection, which commonly presents with a viral prodrome (flu-like symptoms) followed by the characteristic rash. This serology is not consistent with roseola (HHV-6/7), varicella (VZV), or mumps (paramyxovirus), each of which has different causative agents and typical clinical patterns. Recognizing the organism-disease pairing is key for accurate interpretation of pediatric infectious disease testing.

Question 41

The nurse is reviewing the wound culture report from a child’s infected wound caused by a dog bite. Which organism would the nurse suspect to be responsible for the infection?

Accepted Answer

Answer reason: This organism is frequently isolated on wound culture in bite-related infections and is a key reason empiric therapy often targets Pasteurella along with anaerobes. Bartonella henselae is more associated with cat-scratch disease (regional lymphadenitis) rather than typical dog-bite wound cellulitis. Escherichia coli and Francisella tularensis are less characteristic causes of routine dog-bite wound infections.

Question 42

Microbial products can be improved by all of the following EXCEPT?

Accepted Answer

Answer reason: Improving microbial products in industrial microbiology is achieved by increasing yield, productivity, or product quality through selecting/creating better-producing organisms or optimizing growth and production parameters. Isolating new strains, inducing mutations, and genetic modification can enhance biosynthetic pathways, remove regulatory bottlenecks, or improve tolerance to process stresses. Modifying culture conditions (e.g., pH, aeration, nutrients, temperature) can shift metabolism toward the desired product and increase output. Sterilization, however, is a contamination-control step that eliminates microorganisms rather than improving production traits or yields of a producing strain. Therefore it is the exception.

Question 43

Biomass is a renewable energy source derived from the organic matter produced by living organisms. All of the following are sources of biomass EXCEPT?

Accepted Answer

Answer reason: Biomass refers to energy derived from organic matter produced by living organisms or recently living material (e.g., plant matter, microorganisms, and biodegradable wastes). Crops and algae are direct biological sources of organic material that can be converted to fuels. Bacteria contribute to biomass and are central to processes like anaerobic digestion that generate biogas from organic substrates. Landfill sites produce methane through microbial decomposition of organic waste, making them a practical biomass-derived energy source, whereas metal oxidation is an inorganic chemical process and not biomass.

Question 44

Canning preserves food?

Accepted Answer

Answer reason: Food preservation by canning relies on thermal processing to destroy vegetative microorganisms and inactivate enzymes, while also creating a sealed container that prevents recontamination. Commercial canning uses sufficiently high temperatures (often under pressure for low-acid foods) to reduce the risk of spore-formers such as Clostridium botulinum. This heat-based kill step is the defining mechanism of canning, distinguishing it from methods like irradiation or chemical preservatives. Aseptic packaging can be used in some food systems, but it is not what is meant by canning as a preservation method.

Question 45

All of the following are uses for ionizing or ultraviolet radiation EXCEPT?

Accepted Answer

Answer reason: Ionizing and ultraviolet radiation are used primarily for microbial control or pest control by damaging nucleic acids and disrupting replication, not for raising the temperature of foods. Food irradiation is commonly applied to reduce microbial load in items like spices and to control parasites and insects, improving food safety without “cooking” the product. Radiation can also inhibit sprouting in tubers (e.g., potatoes) by interfering with cell division in the sprout tissue. Heating cold food requires thermal energy input (microwave/conventional heating), whereas irradiation aims at disinfection/sterilization rather than warming.

Question 46

Aseptic packaging utilizes which of the following to sterilize laminated paper or plastic prior to filling with food?

Accepted Answer

Answer reason: Heated hydrogen peroxide is commonly used to decontaminate laminated paperboard or plastic before the sterile product is filled, and it can be removed/evaporated with controlled heating and airflow. Autoclaving is unsuitable because many packaging materials would deform or lose integrity under pressurized steam. Radiation methods can be used for some products but are not the standard in many aseptic carton and plastic packaging lines compared with heated hydrogen peroxide surface treatment.

Question 47

Radiation works to preserve foods through?

Accepted Answer

Answer reason: Ionizing radiation preserves food primarily by damaging microbial nucleic acids, causing DNA strand breaks and lethal mutations that prevent replication. This reduces bacterial load and can inactivate many pathogens without relying on temperature changes. High heat is a mechanism of thermal processing (pasteurization/sterilization), not radiation-based preservation. Creating anaerobic conditions or changing pH are separate preservation strategies (packaging/acidification) and are not the primary effect of irradiation.

Question 48

Canning works to preserve foods through?

Accepted Answer

Answer reason: Food canning preserves by reducing viable microorganisms and preventing recontamination. The thermal processing step (high heat for a specified time) kills vegetative bacteria and, when adequate, reduces spores, while the sealed container creates an oxygen-poor environment that limits growth of many aerobes and maintains a barrier to new microbes. An anaerobic environment alone is unsafe because obligate anaerobes (notably spore-formers) can still grow and produce toxin if heat processing is insufficient. Increasing pH is not a defining mechanism of canning (that is more relevant to pickling/acidification), and “mutation of bacterial DNA” is not the intended preservation method.

Question 49

PCR can be used to identify an unknown bacterium because?

Accepted Answer

Answer reason: PCR’s discriminatory power comes from primers that anneal only to complementary target sequences, so only organisms containing that sequence are amplified. By choosing primers for conserved bacterial genes (e.g., 16S rRNA gene regions) or species-specific sequences, amplification indicates the presence of that organism’s DNA in the sample. Other choices describe general properties (polymerase replicates DNA; DNA can be run on a gel; most cells have DNA/RNA) that do not explain why PCR can distinguish one bacterium from another. The key concept is sequence-specific primer binding driving selective amplification for identification.

Question 50

The antimicrobial drug imidazole inhibits sterol synthesis. This would most likely interfere with?

Accepted Answer

Answer reason: Sterols (especially ergosterol in fungi and cholesterol in animals) are key structural components that maintain eukaryotic membrane fluidity and integrity. Imidazole antifungals inhibit ergosterol synthesis, leading to defective membranes with increased permeability and impaired function. Prokaryotic plasma membranes generally lack sterols, so sterol-synthesis inhibition would not be the primary mechanism affecting them. Cell walls (bacterial peptidoglycan or fungal chitin/glucan) and genes are not directly targeted by sterol biosynthesis inhibition.

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Transformation is the transfer of DNA from a donor to a recipient cell?

Repair of damaged DNA, in some instances and mechanisms, might be viewed as a race between an endonuclease and?

Salts and sugars work to preserve foods by creating a?

Which group of microorganisms is most likely to spoil a freshwater trout preserved with salt?

A bacterial culture grown in a glucose-peptide medium causes the pH to increase. The bacteria are most likely?

What is the fate of pyruvic acid in an organism that uses aerobic respiration?

Gallionella bacteria can get energy from the reaction Fe2+ → Fe3+. This reaction is an example of?

Which organism is NOT correctly matched to its energy source?

Which microscope is used to see intracellular detail in a living cell?

The purpose of the ocular lens is to?

Which of the following pairs is mismatched?

Which of the following pairs is mismatched?

Which microscope is used to see internal structures of cells in a natural state?

Simple staining is often necessary to improve contrast in which microscope?

Which microscope achieves the highest magnification and greatest resolution?

Which type of stain is most useful in helping clinicians to decide which antibiotic to prescribe for a bacterial infection?

Which one of the following is most resistant to chemical biocides?

The preservation of beef jerky from microbial growth relies on which method of microbial control?

Which of the following could be used to sterilize plastic Petri plates in a plastic wrapper?

Which of the following pairs is mismatched?

You see acid-fast oocysts in a fecal sample from a patient who has diarrhea. What is the MOST likely cause?

Which of the following is the most effective control for malaria?

In the microscope, you observe multinucleated amoeboid cells with sporangia that form spores. This is a(n)?

You observe a mass of amoeba-like cells that swarm together, form a stalk, and produce spores. This is a(n)?

Molecular biology includes the study of?

Classification of organisms into three domains is based on?

Archaea differ from bacteria in that archaea?

Development of emerging infectious disease can be a result of all of the following EXCEPT?

Which of the following is NOT a characteristic of Neisseria?

Rickettsias differ from chlamydias in that rickettsias?

All of the following bacteria are gram-positive. Which does NOT belong with the others?

Thiobacillus oxidizes inorganic sulfur compounds and reduces CO2. This bacterium is a?

The nonsulfur photosynthetic bacteria use organic compounds as?

Salmonella, Shigella, Yersinia, and Serratia are all?

Which of the following bacteria are responsible for more infections and more different kinds of infections?

Which aerobic gram-negative bacillus is the most common pathogen for all manifestations of urinary tract infection in all groups of clients?

Which microscope is used to see detail of a 300-nm virus?

All of the following are effective for destroying prions EXCEPT?

A client has recently been diagnosed with tuberculosis (TB). The nurse caring for the client anticipates that the client will develop?

A child is admitted to the hospital with flulike symptoms. Diagnostic testing reveals the IgM antibody parvovirus B19 is present. The nurse interprets this finding as being indicative of which condition?

The nurse is reviewing the wound culture report from a child’s infected wound caused by a dog bite. Which organism would the nurse suspect to be responsible for the infection?

Microbial products can be improved by all of the following EXCEPT?

Biomass is a renewable energy source derived from the organic matter produced by living organisms. All of the following are sources of biomass EXCEPT?

Canning preserves food?

All of the following are uses for ionizing or ultraviolet radiation EXCEPT?

Aseptic packaging utilizes which of the following to sterilize laminated paper or plastic prior to filling with food?

Radiation works to preserve foods through?

Canning works to preserve foods through?

PCR can be used to identify an unknown bacterium because?

The antimicrobial drug imidazole inhibits sterol synthesis. This would most likely interfere with?

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