Formative Quiz #3 - Topic 5, 6, 7 Flashcards
What method is used to determine the total number of virus particles present?
a) Plaque assay
b) Differential centrifugation
c) Electron microscopy
d) Hemagglutination assay
c) Electron microscopy
Explanation: Electron microscopy is used to visualize and count individual virus particles, offering precise quantification.
Why does UV irradiation kill microbes?
a) Induces cell lysis
b) Induces DNA damage
c) Damages cellular proteins
d) Prevents uptake of glucose
b) Induces DNA damage
Explanation: UV irradiation causes DNA damage by forming thymine dimers, which disrupt replication and transcription, leading to cell death.
Which medium is used to allow some microorganisms to grow while suppressing others?
a) Enrichment
b) All the choices are correct
c) Selective
d) General purpose
e) Differential
c) Selective
Explanation: Selective media contain agents that inhibit the growth of certain organisms while promoting the growth of others.
To grow only a specific kind of bacteria from a mixed culture, you would plate your cells on what?
a) Selective media
b) Differential media
c) Enrichment media
d) Rich media
a) Selective media
Explanation: Selective media encourage the growth of a particular type of organism while suppressing others, allowing for isolation.
A bacterium that oxidizes compounds containing a single carbon is called:
a) Monomethylotroph
b) Methylotroph
c) Monotroph
d) Methanotroph
b) Methylotroph
Explanation: Methylotrophs are bacteria that utilize single-carbon compounds such as methanol or methane as a source of energy.
Certain species of streptococci play a role in the formation of dental caries.
a) True
b) False
a) True
Explanation: Streptococci, particularly Streptococcus mutans, are known to contribute to dental caries (aka cavities) by producing acids that demineralize tooth enamel.
Nitrogen-fixing species of cyanobacteria fix nitrogen in structures known as:
a) Bacteroids
b) Root nodules
c) Prosthecae
d) Heterocysts
d) Heterocysts
Explanation: Heterocysts are specialized cells in cyanobacteria that create an anaerobic environment necessary for nitrogen fixation.
Within a root nodule, precise oxygen levels are controlled by:
a) Hemoglobin
b) Leghemoglobin
c) Opines
d) Bacteroids
b) Leghemoglobin
Explanation: Leghemoglobin is a molecule in root nodules that regulates oxygen levels to protect nitrogenase, which is sensitive to oxygen.
All bacteria have an electron transport system:
a) TRUE
b) FALSE
b) FALSE
Explanation: Strict fermenters, such as lactic acid bacteria, lack an electron transport system and rely on fermentation for energy production.
To classify streptomyces, you could use the following feature:
a) Different types of sporebearing structures
b) Whether it can produce antivirals
c) Different smells based on the type of geosmin produced
d) Location of its flagella
a) Different types of sporebearing structures
Explanation: Streptomyces are distinguished by their ability to produce a variety of sporebearing structures that aid in their classification.
Which of the following is not a member of the enteric group of bacteria?
a) Pseudomonas
b) Salmonella
c) Escherichia coli
d) Enterobacter
a) Pseudomonas
Explanation: Pseudomonas is not part of the enteric group, which includes bacteria like Salmonella, E. coli, and Enterobacter that inhabit the intestinal tract.
A neutrophile grows well at what pH?
a) Between 5.5 and 8.5
b) Less than 5.5
c) Less than 3.5
d) More than 8.5
a) Between 5.5 and 8.5
Explanation: Neutrophiles thrive in environments with a neutral pH range, typically between 5.5 and 8.5.
What does triclosan do to disinfect surfaces?
a) Interferes with protein synthesis and amino acid metabolism
b) Interferes with cellular respiration
c) Attacks cell membranes (by interfering with fatty acid synthesis)
d) Interferes with DNA synthesis
c) Attacks cell membranes (by interfering with fatty acid synthesis)
Explanation: Triclosan is an antimicrobial agent that disinfects surfaces by targeting bacterial cell membranes. It inhibits the enzyme FabI (enoyl-acyl carrier protein reductase) an enzyme that plays a critical role in fatty acid synthesis in bacteria. By disrupting this process, triclosan compromises the integrity of the bacterial cell membrane, ultimately causing cell death. This mechanism makes it effective against a wide range of bacteria.
What types of cells are capable of being attacked by Bdellovibrio?
a) Acid-fast bacteria
b) Gram-negative bacteria
c) Gram-positive bacteria
d) Endospore-forming bacteria
b) Gram-negative bacteria
Explanation: Bdellovibrio primarily targets Gram-negative bacteria by entering their periplasm and disrupting their cellular processes.
Nitrosomonas…
a) Is capable of complete ammonia oxidation to nitrate
b) Has an ammonia monooxygenase
c) Is an ammonia oxidizing archaeon
d) Oxidizes nitrite to nitrate
b) Has an ammonia monooxygenase
Explanation: Nitrosomonas uses the enzyme ammonia monooxygenase to oxidize ammonia to nitrite in the nitrogen cycle.
Nonsporulating Gram-positive cocci that are aerobic and catalase positive would most likely be members of the genus:
a) Chlamydia
b) Mycoplasma
c) Staphylococcus
d) Streptococcus
c) Staphylococcus
Explanation: Staphylococcus species are nonsporulating, Gram-positive cocci that are aerobic and catalase positive, distinguishing them from other genera.
What are drawbacks of direct counts from a Petroff-Hauser counting chamber?
a) Bacterial counts are generally too high to count accurately
b) The chambers are difficult to use accurately
c) Labor intensive and counts both living and dead cells
d) Bacteria are too small to count under a microscope
c) Labor intensive and counts both living and dead cells
Explanation: The Petroff-Hauser chamber method is labor-intensive and does not differentiate between live and dead cells, leading to potential inaccuracies.
Mycolic acids in the cell wall contribute to the acid-fastness of lactic-acid bacteria.
a) True
b) False
b) False
Explanation: Lactic-acid bacteria lack mycolic acids in their cell walls, which are a characteristic of acid-fast bacteria like Mycobacterium species.
What would you have to do to establish a continuous culture?
a) Nothing, cells will keep growing indefinitely without any manipulation
b) Continually add more medium to the culture
c) Continually add fresh cells to the culture
d) Continually add and remove medium to the culture
d) Continually add and remove medium to the culture
Explanation: A continuous culture requires the addition of fresh medium and removal of spent medium to maintain a steady-state growth phase.
Which of these is the most widely used chemical for energy conservation to support cellular processes?
a) Glucose
b) NADH
c) Pyruvate
d) Citrate
e) ATP
e) ATP
Explanation: ATP is the primary molecule used by cells for energy transfer, powering various cellular processes. Glucose, citrate, NADH, and pyruvate are energy sources that are broken down or metabolized by the cell to produce ATP.
How does freezing protect foods against spoilage?
a) Bacteria can’t replicate at low temperatures
b) Biochemical reactions do not work efficiently at low temperatures
c) Ice crystals form in the foods and break open the microbial cells
d) All of these choices
d) All of these choices
Explanation: Freezing slows microbial activity, inhibits biochemical processes, and can physically damage cells with ice crystals.
Yes, all these statements are true.
Freezing protects food by:
- Preventing bacterial replication, as low temperatures inhibit the growth and division of most microorganisms.
- Reducing the efficiency of biochemical reactions necessary for microbial metabolism and survival.
- Forming ice crystals, which can physically puncture and damage microbial cell walls, leading to cell death.
These combined effects make freezing an effective method for delaying food spoilage.
If scaled to our own size (1.5 meters), which bacterium would set land-speed records in a race?
a) Sprillum
b) Bdellovibrio
c) Pseudomonas
d) Nitrospira
b) Bdellovibrio
Explanation: Bdellovibrio moves at an incredible speed of 100 cell lengths per second, making it one of the fastest bacteria.
Why does heat work to eliminate microbes from a substance?
a) Heat causes the cells to expand
b) Most microbes don’t like to grow at high temperatures
c) Heat causes proteins to denature and membrane collapse
d) Heat dehydrates the cells
c) Heat causes proteins to denature and membrane collapse
Explanation: Heat disrupts microbial proteins and membranes, rendering them nonfunctional and leading to cell death.
Many species of nitrifying bacteria have internal membrane systems that are the location of key enzymes, ammonia monooxygenase and nitrite oxidase, which are involved in nitrification.
a) True
b) False
a) True
Explanation: Nitrifying bacteria utilize specialized internal membranes to house enzymes for ammonia and nitrite oxidation during nitrification.
Ammonia monooxygenase is an enzyme used by nitrifying bacteria to oxidize ammonia (NH₃) into hydroxylamine (NH₂OH) as the first step in nitrification. Nitrite oxidase is another key enzyme that catalyzes the oxidation of nitrite (NO₂⁻) into nitrate (NO₃⁻), completing the process. Both enzymes are critical for the conversion of nitrogen compounds into forms usable by plants and are localized in specialized internal membrane systems for efficiency.
What is the growth rate for a culture that has a generation time of 0.5 hours?
a) 2 hr
b) 1 hr
c) 1 hr-1
d) 2 hr-1
d) 2 hr-1
Explanation: Growth rate is the inverse of generation time. A generation time of 0.5 hours corresponds to a growth rate of 2 generations per hour.
Some nitrogen-fixing bacteria…
a) Oxidize nitrogen gas to ammonia
b) Use hemoglobin to bind oxygen, preventing it from deactivating the nitrogenase
c) Include Nitrospira, Nitrobacter, and Nitrosomonas
d) May be in close associations with plant roots
d) May be in close associations with plant roots
Explanation: Many nitrogen-fixing bacteria form symbiotic relationships with plant roots, facilitating nitrogen fixation in exchange for nutrients.
Which is true about methanotrophs?
a) They are obligate C1 utilizers
b) They have a methane dioxygenase for metabolizing methane
c) They are obligate anaerobes
d) They are found mainly within the rumen of animals
a) They are obligate C1 utilizers
Explanation: Methanotrophs specialize in utilizing one-carbon (C1) compounds like methane as their energy and carbon source.
The nucleocapsid of a virus encloses what?
a) Envelope
b) Genome
c) Enzymes
d) Proteins
b) Genome
Explanation: The nucleocapsid is the protein shell of a virus that directly encloses its genetic material, which may be DNA or RNA.
Which statement is TRUE with respect to the electron transport system?
a) A proton motive force is generated as electrons move through the system to a terminal acceptor
b) In prokaryotes, protons are transported into the cell as electrons move through the system
c) ATP is produced by a process called substrate-level phosphorylation
d) The electron transport system accepts electrons directly from glucose
e) In bacteria, the electron transport system is located in the cytoplasm
a) A proton motive force is generated as electrons move through the system to a terminal acceptor
Explanation: As electrons pass through the electron transport system, protons are pumped across the membrane, creating a gradient that drives ATP synthesis.
What is a bacterial colony?
a) All the bacteria in your culture
b) Genetically equivalent cells
c) A mound of clonal cells originally derived from one cell
d) An artifact of growth on a particular medium
c) A mound of clonal cells originally derived from one cell
Explanation: A bacterial colony represents a visible group of genetically identical cells that originated from a single cell.
Bacterial genes that direct the steps in nodulation of a legume are called:
a) Lux genes
b) Idc genes
c) Vir genes
d) Nod genes
d) Nod genes
Explanation: Nod genes are involved in the nodulation process, enabling bacteria to form symbiotic relationships with legumes for nitrogen fixation.
Why might you want to use turbidity to measure cell counts?
a) Rapid and inexpensive for a microbiology lab
b) You would not want to use this technique as it is only accurate over a narrow range
c) It does not require large cell volumes as compared to plate counts
d) Can be done by eye, without requiring access to lab equipment
a) Rapid and inexpensive for a microbiology lab
Explanation: Turbidity measurements offer a quick and cost-effective way to estimate bacterial cell density, particularly when precision is less critical.
For plate counts, why are numbers less than 10 and higher than 300 usually excluded?
a) Numbers less than 10 are not statistically significant and more than 300 colonies on a plate usually have too much overlap to be accurately counted
b) Numbers less than 10 are not statistically significant but more than 300 colonies are okay
c) Numbers less than 10 are not statistically significant and more than 300 colonies are too hard to count
d) Numbers less than 10 are okay to use but more than 300 colonies on a plate usually have too much overlap to be accurately counted
a) Numbers less than 10 are not statistically significant and more than 300 colonies on a plate usually have too much overlap to be accurately counted
Explanation: Accurate plate counts require a balance; too few colonies lack statistical power, and too many colonies overlap, making counts unreliable.
In a Winogradsky column, green sulfur bacteria are likely to be found where?
a) In the middle where it is anoxic and has available sulfate
b) At the top where they have access to both oxygen and light
c) In the middle where it is anoxic and has available hydrogen sulfide
d) At the very bottom of the column where they degrade organic matter into carbon dioxide
c) In the middle where it is anoxic and has available hydrogen sulfide
Explanation: Green sulfur bacteria thrive in anoxic zones with hydrogen sulfide, which they use for photosynthesis.
Polymer degradation is a feature of which group of microorganisms?
a) Anaerobic chemoheterotrophs
b) Non-sporulating pseudomonads
c) Sporulating Gram-positives
d) Sporulating Gram-negatives
c) Sporulating Gram-positives
Explanation: Sporulating Gram-positive bacteria are known for their ability to degrade polymers, which is important for nutrient cycling.
Oxygenic cyanobacteria contain…
a) Only a single type of pigment, chlorophyll a
b) Specialized membranes for photosynthesis
c) Differentiated cells capable of nitrogen oxidation
b) Specialized membranes for photosynthesis
Explanation: Cyanobacteria have thylakoid membranes, which are specialized structures that enable efficient photosynthesis.
All Proteobacteria are:
a) Gram-negative
b) Gram-variable
c) Gram-positive
d) Acid fast
a) Gram-negative
Explanation: Proteobacteria is a diverse phylum that includes all Gram-negative bacteria, characterized by their outer membrane structure.
To favour the growth of one kind of bacteria over another, what kind of media would you use?
a) Selective media
b) Differential media
c) Enrichment media
d) Rich media
c) Enrichment media
Explanation: Enrichment media provide a specific advantage to one group of bacteria without actively suppressing others. If suppression is involved, it would be selective media.
Why can a streak plate be used to isolate a pure culture of bacteria?
a) Every bacterium can be grown on an agar plate
b) They are simple and inexpensive to do
c) You can get lots of isolated colonies
d) Each original cell gives rise to one colony
d) Each original cell gives rise to one colony
Explanation: A streak plate allows individual cells to grow into separate colonies, ensuring isolation of a pure culture from a mixed sample.
One genus of free-living nitrogen-fixing bacteria is:
a) Beijerinckia
b) Xanthomonas
c) Burkholderia
d) Acetobacter
a) Beijerinckia
Explanation: Beijerinckia is a genus of free-living nitrogen-fixing bacteria, known for its role in nitrogen fixation without forming symbiotic relationships.
To grow a bacterial colony, what kind of media do you need?
a) Liquid
b) Solid
c) Complex
d) Defined
b) Solid
Explanation: A colony is a visible mass of cells that develops on solid media, originating from a single “mother cell”
Which of these is TRUE for a chemolithoautotroph?
a) Inorganic molecules as energy sources and inorganic carbon as a carbon source
b) Organic molecules as electron sources and inorganic carbon as a carbon source
c) Inorganic molecules as electron sources and organic carbon as a carbon source
d) Inorganic molecules as energy sources and organic carbon as a carbon source
e) Organic molecules as energy sources and organic carbon as a carbon source
a) Inorganic molecules as energy sources and inorganic carbon as a carbon source
Explanation: Chemolithoautotrophs use inorganic molecules for energy and electron sources while fixing inorganic carbon for growth.
Which medium is used to allow slow-growing microbes to gain a competitive growth advantage?
a) Selective
b) Differential
c) Enrichment
d) All of the choices are correct
e) General purpose
c) Enrichment
Explanation: Enrichment media are formulated to provide conditions favorable to slow-growing microbes, giving them a competitive advantage.
Heterofermentative lactic acid bacteria produce _______ from the fermentation of sugars.
a) Lactic acid plus formic and pyruvic acids
b) Only lactic acid
c) Lactic acid plus formic acid
d) Lactic acid plus ethanol and carbon dioxide
d) Lactic acid plus ethanol and carbon dioxide
Explanation: Heterofermentative lactic acid bacteria ferment sugars to produce multiple products, including lactic acid, ethanol, and carbon dioxide.
Myxobacteria…
a) Possess a very small chromosome (half the size of E. coli)
b) Use intercellular communication and multicellular life stages
c) Are strict chemolithoheterotrophs
d) Form vegetative cells
b) Use intercellular communication and multicellular life stages
Explanation: Myxobacteria are unique for their cooperative behavior and multicellular structures, which allow them to adapt to diverse environments.
What pore size would you need to remove most bacteria from a solution for routine sterilization purposes?
a) 0.1 µm
b) 100 µm
c) 10 µm -100 µm
d) 0.2 µm - 0.45 µm
d) 0.2 µm - 0.45 µm
Explanation: Pore sizes of 0.2-0.45 µm are effective for filtering out most bacterial cells, making them ideal for routine sterilization.
Enterics…
a) Are Gram-positive, spore-forming, lactose-fermenting bacteria
b) May parasitize plants (e.g., Crown-gall disease)
c) Are used as warning signs for potential pathogens
d) Are strict aerobes
c) Are used as warning signs for potential pathogens
Explanation: Enteric bacteria are indicators of potential pathogens in environments like water, as they signify contamination.
The earthy odor of soil is caused by the production of a series of streptomycete metabolites called:
a) Heterocysts
b) Geosmins
c) Antibiotics
d) Cord factors
b) Geosmins
Explanation: Geosmins, produced by Streptomyces species, are responsible for the characteristic earthy smell of soil.
Which of the following processes will be affected most by a change in temperature?
a) DNA stability
b) Enzyme activity
c) Carbohydrate structure
d) Nutrient availability
b) Enzyme activity
Explanation: Enzyme activity is highly sensitive to temperature changes, which can alter enzyme shape and function, significantly affecting biological processes.
Pseudomonads…
a) Are highly specialized and perform specific functions in the environment
b) Have peritrichous flagella
c) Are found in many environments and can use many organic energy sources
d) Prefer anoxic environments such as soil/water interfaces
c) Are found in many environments and can use many organic energy sources
Explanation: Pseudomonads are versatile organisms capable of thriving in various environments by metabolizing diverse organic compounds.
Streptococcus pyogenes is an example of a lactic acid bacterium that:
a) Is used extensively in fermented food products such as buttermilk and cheese
b) May cause cavities
c) Can cause necrotizing fasciitis
d) Is commonly found on human and animal skin
c) Can cause necrotizing fasciitis
Explanation: Streptococcus pyogenes is known for causing severe infections like necrotizing fasciitis, also referred to as ‘flesh-eating disease’
