Microbiology and Immunology 6400 Oral Intermicrobial Interactions Practice Test

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• Which enzyme converts superoxide to hydrogen peroxide in S. mutans?
• Define microbial antagonism and give an oral example.
• What type of organism primarily carries out nitrate to nitrite conversion in the oral cavity?
• The addition of what can inhibit coaggregation?
• In periodontal biofilms, increases in red complex bacteria are associated with what outcome?
• What pH threshold is commonly considered critical for enamel demineralization?
• Which of the following is NOT a member of the red complex?
• Hydrogen peroxide produced by oral commensal streptococci can react with nitrite to form other reactive nitrogen species such as:
• What mechanisms contribute to antibiotic resistance in dental plaque biofilms?
• Which imaging modality is used to obtain three-dimensional architecture and viability mapping of dental biofilms?
• List the bacteria commonly referred to as the red complex.
• The Fenton reaction converts hydrogen peroxide into which reactive species?
• Which diagnostic approach provides broad profiling of all genetic material in a sample, including bacteria, archaea, and viruses?
• Interactions between microbial species can be what two types?
• What is a common in vitro method to study multi-species dental biofilms?
• Name a major structural adhesion factor used by oral bacteria to attach to surfaces and other microbes?
• What is horizontal gene transfer and why is it significant in oral biofilms?
• What imaging technique is widely used to visualize dental biofilms and structure?
• Which pair of microorganisms is commonly found in early dental plaque?
• Which of the following is an example of aciduric bacteria?
• Which statement correctly describes the action of bacteriocins in Gram-positive bacteria?
• Name a caries-associated genus and describe its role in progression.
• Which statement about SpxB and hydrogen peroxide production is correct?
• Arginine is primarily metabolized to ornithine, ammonia, and CO2 by abundant oral bacteria.
• Which organism is described as a homeostatic commensal able to mitigate pathogenic activity through modulation of host epithelial cell signaling?
• What three nitrate-rich vegetables act as a prebiotic, fueling these bacteria and shifting the oral microbiome toward health-associated species like Rothia and Neisseria?
• What effect does nitric oxide–derived reactive nitrogen species have on bacterial biofilms?
• Which statement is true regarding growth on pure human saliva?
• In Gram-negative bacteria, bacteriocins can inhibit the activity of what three things?
• Which component directly eliminates superoxide radicals in S. mutans?
• What does urea get hydrolyzed into?
• Oral bacteria can also interact with host cells to modify _________ of other organisms.
• Where do hydrogen peroxide interactions occur in biofilms due to oxygen requirement?
• What is a potential application of bacteriocins?
• Describe cross-feeding between Veillonella and Streptococcus species in dental plaque.
• During fasting, glycan foraging significantly changes pH.
• Name two early colonizers and two late colonizers of the dental pellicle, and summarize their roles.
• Catalase decomposes hydrogen peroxide into which products?
• Where does Veillonella obtain lactate?
• Arginine is primarily catabolized by abundant organisms in dental plaque. Which group best identifies these organisms?
• Which signaling system in Streptococcus mutans triggers genetic competence for DNA uptake?
• What Gram-negative facultative anaerobic bacterium inhabits the human oral cavity and is a proposed causative agent of localized aggressive periodontitis?
• Name two key salivary antimicrobial components and their actions.
• What readouts indicate a dysbiotic shift in periodontal biofilms in experimental models?
• What organism produces catalase and has been shown to protect S. mutans from hydrogen peroxide oxidative stress with adherence required?
• Which organism buffers the pH in the oral environment?
• Which factor is described as critical for intermicrobial interactions to behave normally?
• What does the nitrate-nitrite-NO pathway generate independently of our own host enzymes?
• What carbon source does Veillonella prefer?
• Alkyl hydroperoxide reductase (ahp) function is to
• What does the slo operon encode?
• Which organism is noted for producing catalase and protecting S. mutans from hydrogen peroxide oxidative stress with adherence?
• During fasting, to what level do host carbohydrates drop?
• Which salivary antimicrobial component is part of the peroxidase system that helps generate antimicrobial oxidants?
• Hydrogen peroxide is produced during the conversion of pyruvate to acetyl phosphate by the action of the enzyme ________.
• Which pattern recognition receptors are important in detecting oral biofilm components in epithelial cells?
• In nitrate reduction, which molecule serves as an intermediate before forming nitric oxide?
• What reaction generates ROS from hydrogen peroxide?
• How do saliva flow and buffering capacity affect plaque acid neutralization?
• What molecule, in free form, is secreted at concentrations of about 50 μM in saliva?
• At about what pH do health-associated streptococci stop metabolizing?
• Give an example of microbial antagonism in the oral cavity and its consequence.
• Cooperation within microbial consortia can improve microbial metabolism, often referred to as _________.
• Which statement best describes the RANKL/OPG axis in periodontal bone loss?
• Peroxynitrite formation in this oral context is described as being produced from hydrogen peroxide reacting with nitrite.
• During fasting, salivary glycans serve as a carbohydrate source for bacteria.
• What is the role of neutrophils in gingival crevicular fluid against plaque biofilms?
• Which of the following is NOT a product of Veillonella's lactate metabolism?
• Catalase is not present in all Streptococcus species.
• Which organism is typically among the initial colonizers of dental plaque?
• Which organism is a Gram-negative facultative anaerobe in the oral cavity associated with localized aggressive periodontitis?
• Competition is often mediated by ________ where individuals capitalize on public goods produced by others while not contributing in the same extent.
• How does the acquired enamel pellicle influence reattachment after disruption?
• Describe the oxygen gradient in dental plaque and how it shapes community composition.
• What term describes a partner required for colonization in a niche?
• T/F: Veillonella obtains lactate through its own production.
• Veillonella allows S. mutans to have continued ________.
• What is coaggregation in the context of the oral biofilm, and what role does it play in initial biofilm formation?
• What interaction between oral bacteria is done by diffusable signaling?
• What are coaggregations in the context of oral bacteria?
• Which statement is true about acid production by health-associated streptococci?
• What molecule do commensal streptococci produce during the conversion of pyruvate to acetyl phosphate?
• During fasting, what carbohydrate source do bacteria use?
• Which of the following best describes Veillonella's ecological role with lactate?
• Environmental sensing can lead to changes in bacterial __________ that alters metabolism or other aspects of physiology, providing advantages/disadvantages to fitness and changing interaction strategies.
• Humans lack efficient ________, so we rely on commensal bacteria to convert dietary nitrate into nitrite, which is then further reduced to NO.
• Bacteria encode for proteins known as _________ that can break specific bonds present within glycans.
• Is Veillonella gram positive or negative?
• Which statement best summarizes the oxidative stress response in S. mutans?
• In microbial communities, the exploitation of public goods produced by others by not contributing is called what?
• What term describes binding interactions between different oral bacteria that enable multi-species aggregates?
• Which factor coordinates gene expression for adhesion, EPS production, metabolism, and virulence promoting maturation and stability of the biofilm?
• How does Candida albicans interact with bacterial community in oral biofilms?
• Which term best describes the class of molecules that includes nitric oxide and peroxynitrite in this context?
• Oral bacteria, besides S. mutans, can be sensitive to the presence of hydrogen peroxide through generation of _________.
• Which statement is true regarding coaggregation inhibition?
• What is the general role of quorum sensing in oral biofilm maturation?
• When blood passes by the _______, nitrate from the blood is actively concentrated to mM levels into _______.
• Which compound is not a reactive nitrogen species?
• What interaction between oral bacteria is done by physical contact?
• What term describes the organization of tasks among community members to improve metabolism?
• What describes when one microbe produces a nutritional source for another?
• How are glycosidases distributed between different species of oral bacteria?
• What molecule is in all salivary secretions and present at concentrations of 3-10 mM?
• Which organism is described as bridging species in oral biofilms?
• T/F: Cariogenic species produce hydrogen peroxide.
• Denture-related stomatitis is commonly linked to the presence of which organism in the denture biofilm?
• Give an example of a bridging organism that links early and late colonizers via coaggregation.
• Which type of distance between microbes is critical for their interactions to behave normally?
• Why is dental plaque considered a structured ecosystem rather than random microbial assortment?
• Which metal substitutes for iron in some enzyme reactions in S. mutans?
• Dpr in S. mutans functions as
• Which of the following is not a major risk factor for caries development?
• Distinguish between acidogenic and aciduric bacteria with examples from the oral cavity.
• Which statement best identifies late colonizers in dental plaque formation?
• Why do these streptococci stop metabolizing?
• Which statement best describes the purpose of 16S rRNA gene sequencing in oral microbiology?
• Some organisms serve as bridging species by adhering to multiple different species. Which term describes this?
• Arginine is converted into which products?
• What organism can modify host epithelial cell responses by upregulating the host transcription factor ZEB2 which controls host inflammatory responses?
• Bacteriocins are used by many oral streptococci to combat other species in the oral cavity. Which species is explicitly named as containing bacteriocins?
• What is acquired enamel pellicle and how does it influence initial bacterial adhesion?
• What is the role of manganese transporters (slo operon) in S. mutans?
• Once nitrate is in saliva, oral bacteria can reduce the nitrate into _______, where it again enters the bloodstream via the gut and is then further reduced to _______,
• Hydrogen peroxide production requires which environment?
• Is Veillonella anaerobic or aerobic?
• In Streptococcus mutans, how do competence-stimulating peptide and general quorum sensing differ?
• Some species also contain __________ which can further reduce nitrite into nitric oxide.
• The addition of arginine to the oral environment can increase buffering against organic acid insults. This environmental effect is best described as which of the following?
• Nitric oxide acts as an antimicrobial reactive nitrogen species.
• T/F: Metabolism of ALL oral streptococci will result in lowering of environmental pH.
• Which cytokines are commonly elevated in periodontal inflammation and drive tissue destruction?
• Which two genera are named as Veillonella's potential coaggregating partners?
• True/False: Cooperation generally does not improve microbial metabolism.
• Which interaction type is described by diffusible, soluble signals rather than direct contact?
• What organism can interact with the same cells to antagonize ZEB2 expression?
• What is the role of Lactobacillus species in caries progression?
• In Gram-positive bacteria, bacteriocins form ______ in the cell membrane.
• Urea is hydrolyzed into ammonia and CO2 by bacterial ureases which are produced by some oral bacteria such as _________.
• What type of bacteria continue metabolism at low pH?
• In nitrate reduction, nitrite is an intermediate; which molecule corresponds to nitrite?
• Which organism cannot produce hydrogen peroxide due to lack of the SpxB gene?
• Which of the following is a mechanism by which S. gordonii inhibits competitors?
• Veillonella species make up approximately what percentage of bacterial species in oral biofilms?
• Which enzyme mediates the reduction of nitrate to nitric oxide in bacteria?
• After nitrite is formed in saliva, where does it primarily travel to for further reduction to nitric oxide?
• What are the two ways S. gordonii inhibits competitors?
• What does one glycosidase act on?
• Are Veillonella species early colonizers, bridging species, or late colonizers?
• Which statement best characterizes the need for a colonization partner?
• Nitrate reducing oral bacteria are essential for what pathway?
• Which site primarily performs the initial reduction of nitrate to nitrite in the body, contributing to systemic NO production?
• What type of adhesion occurs in coaggregation?
• Which best describes hydrogen peroxide production among oral bacteria?
• Multiple glycosidases are required to fully utilize a _______ and break down individual carbohydrates down to the ________ core.
• Why does dental calculus serve as a stable substrate for microbial colonization?
• Which best describes Veillonella's interactions with other oral bacteria?
• Which of the following bacteria is most commonly associated with dental caries due to acid production?
• Bacteriocins are used by different bacterial species as __________ to either hold onto or invade a niche colonized by other microbes. Many oral streptococci contain bacteriocins, including Streptococcus mutans, which is used to combat other species present in the oral cavity.
• Is S. mutans sensitive to hydrogen peroxide?
• S. gordonii is seen as a _________ that is capable of mitigating the activity of a more pathogenic organism through modulation of host epithelial cell signaling.
• Which term describes an organism that adheres to multiple species to facilitate colonization?
• What is the Stephan curve and why is it important for understanding caries risk?
• How can oral biofilms influence systemic health, specifically endocarditis risk?
• Host-derived macromolecules present in saliva, such as salivary mucins, are ________.
• Which of the following is a potential application of bacteriocins?
• Nitrate reduction in the oral environment leads to the generation of nitric oxide, which is a type of:
• Salivary mucins are which type of molecules?
• Which enzyme reduces hydrogen peroxide in S. mutans?
• T/F: A single bacterial species is able to grow in pure human saliva alone.
• Arginine is abundant in which of the following in the oral environment?
• What are extracellular polymeric substances and what role do they play in oral biofilms?
• Th17 cells contribute to periodontal tissue destruction by secreting which cytokine that recruits neutrophils?
• What surface structures facilitate adhesion among oral bacteria and influence coaggregation?
• Describe how Porphyromonas gingivalis LPS can modulate host immune responses.
• Streptococcus mutans does not encode for the ________ gene and is unable to make hydrogen peroxide.
• Which compound is present in saliva at approximately 50 μM in free form and is an amino acid?
• Which salivary antimicrobial component is primarily responsible for sequestering iron and inhibiting growth?
• Which enzyme is commonly involved in degrading hydrogen peroxide in bacteria and fungi?
• What is nitric oxide a critical molecule for?
• What is the relationship between dental plaque and calculus mineralization?
• Which factor is directly influenced by gene expression changes in oral bacteria during interspecies interactions?
• Cross feeding is categorized as which type of interaction?
• Which two species are classic early colonizers of the dental pellicle?
• Which of the following is a major virulence factor of Porphyromonas gingivalis and what is its function?
• S. mutans interacts with other pathogens under oxidative stress by which mechanism?
• How does dental calculus form and why is it a stable substrate for microbes?
• Which organism NOT inhibited by the reactive nitrogen species generated in this oral context?
• Oral bacteria use _________ to detect changes in their environment or the presence of other microbes.
• Which trio of organisms has been reported to be inhibited by this RNS generation?
• In dental plaque biofilms, arginine breakdown to ornithine, ammonia, and CO2 is primarily performed by which organisms?
• Which probiotic strains are cited as examples used to improve oral health by modulating biofilm composition and host responses?
• During early dental plaque formation, what is the role of pellicle binding by Actinomyces and Streptococcus?
• Veillonella has the ability to adhere or coaggregate with a variety of species including both ________ and ________.
• What varies with feeding and fasting?
• Explain the ecological plaque hypothesis and how it relates to caries and periodontal disease.
• Which pattern recognition receptor families are important in detecting microbial components in the oral epithelium?
• Which two actions must microbes contend and adapt for successful colonization?
• Define the keystone pathogen concept in periodontitis and name the organism most associated with it.
• What does Veillonella convert lactate into?
• Which term describes bacteria that can continue metabolism at low pH and produce acid?
• Hydrogen peroxide production by select species has been shown to play a role in ______ between species within biofilms.
• Which bacteria are commonly studied as pioneers in dental plaque formation and can influence community assembly?
• What percentage of bacterial species in biofilms do Veillonella make up?
• In oral biofilms, Streptococcus sanguinis inhibits Streptococcus mutans through hydrogen peroxide production. What type of interaction is this?
• Dpr is a DPS-like peroxide resistance gene.
• Which organism antagonizes ZEB2 expression in host epithelial cells?
• In periodontal disease, progression of bone loss is driven by increased activity of which axis component relative to its counterpart?
• When the host feeds, carbohydrates are present at what level?
• Which spirochete is commonly implicated in periodontal tissue destruction?
• These interactions can lead to changes in gene expression that increase or decrease production of virulence factors.
• Reactive nitrogen species described in this context can disperse biofilms, alter bacterial physiology, and reduce viability.
• What is the term for slow-growing cells within a biofilm that contribute to antibiotic tolerance?
• Which gene names correspond to the enzymes converting nitrate to nitrite and nitrite to nitric oxide?
• Which organism upregulates ZEB2 in host epithelial cells?
• Which statement best describes the role of early colonizers in pellicle development?
• What are denture-related biofilms and their clinical significance?
• Veillonella can be described as which combination of Gram stain and oxygen requirement?
• Identify three major risk factors for dental caries development.
• Is cross feeding considered cooperative or competitive?
• How do Actinomyces and Streptococcus interact during initial plaque formation?
• One of the many effects that NO has on the body is vasodilation, thereby __________.
• Which organism is NOT inhibited by the reactive nitrogen species generated by oral commensal streptococci?
• Name two probiotic approaches used to improve oral health.
• Nitrite is formed as an intermediate in nitrate reduction.
• Veillonella affects pH by:
• Which statement best describes how glycosidases are distributed among oral bacteria species?
• Biofilms allow bacteria to share what?
• Several genera of oral bacteria contain ________ that can convert dietary nitrate into nitrite.
• What are toxins produced by bacteria to inhibit the growth of similar or closely related bacterial strains?
• Which statement best describes AI-2 and LuxS in oral biofilms?
• What is the role of Th17 cells in the pathogenesis of periodontal disease?
• Nitrate-rich vegetables act as a prebiotic that fuels these bacteria and shifts the oral microbiome toward health-associated species like Rothia and Neisseria.
• Which enzyme class cleaves glycosidic bonds in carbohydrates?
• What diagnostic approaches are used to characterize oral microbiota?
• ___________ of oral bacteria together in aggregates/biofilms allows multiple species to come together to break down glycans and supply required nutrients.
• What is the role of glucosyltransferases and glucans in dental plaque formation?
• Nitrate is consumed and eventually taken up by the ________ in the _________.
• Which statement best describes the carbohydrate source during fasting?