Microbiology Test 2
When a virus enters a host cell in which it can replicate, the process is called a(n)
Infection
The most frequent way in which small regulatory RNA molecules exert their effects is by
base pairing with other RNA molecules that have regions of complementary sequence.
T/F An RNA genome itself serves as mRNA in negative-stranded RNA viruses.
False
T/F Gram-negative bacteria are responsible for causing over 60% of foodborne illness.
False
T/F Ideally, microbes should be eliminated from all foods.
False
T/F If properly constructed, a Winogradsky column can be used to isolate pure cultures.
False
T/F The MPN technique is rarely applied in the food industry because any microbial presence in food is unsafe.
False
T/F Viroids infect only fungi.
False
If a researcher wanted to compare the enzymatic capacity to degrade compounds in a water column at various depths under a specific set of conditions, which would be the most useful approach?
Metaproteomics
Both ammonium (NH4+) and nitrate (NO3-) are assimilated by primary producers, but ammonium is the preferred form of nitrogen for fertilizers used in agriculture because __________.
Nitrate leaches out of soils easily due to its negative charge
Irradiation of food uses
Non-ionizing radiation
Microarrays that have been designed to screen samples for specific groups of bacteria are called __________.
Phylochips
In certain circumstances, a single regulatory protein controls multiple operons. This situation would be called a(n) ___________________.
Regulon
When more than one operon is under the control of a single regulatory protein, the operons are collectively called a(n)
Regulon
Which operons are always transcribed unless deactivated?
Repressible operons
Which type of regulator(s) specifically binds to operator regions of DNA?
Repressors
Which of the following is NOT characteristic of a coliform?
Resistant to chlorinatio
Some organisms are capable of using aerobic respiration or anaerobic respiration but use aerobic respiration preferentially. Why is aerobic respiration favored?
Respiration with oxygen as a terminal electron acceptor generates more energy than respiration with other terminal electron acceptors.
Salmonellosis is most frequently caused by
Salmonella enterica serovars Typhimurium and Enteriditis.
Which disease did Stanley Prusiner first identify as being caused by prions?
Scrapie
Microarrays are useful for assessing
gene expression and the presence of specific rRNA sequences.
Select the correct sequence of steps as energy is extracted from glucose during cellular respiration.
glycolysis---> acetyl CoA---> Citric acid cycle ----> electron transport chain
Which technique would be used to estimate the concentration of naturally occurring Escherichia coli in a wastewater sample?
most probable number (MPN) method
T/F Although the domain Archaea contains many acidophilic organisms, there are still many others within the domain that grow well in environments with a neutral pH.
True
T/F Campylobacter infections are the most common foodborne infections in the United States.
True
T/F Food poisoning generally results from the ingestion of food containing microbial toxins.
True
T/F Many microbial habitats are unsuitable for plants and animals.
True
T/F Mass-processed ground meat is a particularly common source of infection with EHEC.
True
T/F Norovirus is commonly transmitted by the fecal-oral route.
True
T/F Not all coliforms are pathogenic.
True
What two molecules are produced by the light reactions and used to power the Calvin cycle?
ATP and NADPH
What is the intermediate product formed by pyruvic acid during alcoholic fermentation?
Acetaldehyde
What is the inducer molecule in the lac operon?
Allolactose
What is the function of GTP?
An energy carrier
Why is the tryptophan operon turned off in the presence of tryptophan?
Tryptophan binds to and activates the repressor proteins; the repressor proteins, in turn, bind to the operator, preventing transcription.
What is the net production of ATP in glycolysis?
Two ATP
Which of the following viral genomes could be directly transcribed to make proteins?
Class IV ssRNA (+) viruses
A naked virus lacks a capsid.
False
Archaea and Bacteria dominate the upper 100 m of the open ocean while viruses dominate depths greater than 100 m.
False
T/F A bacteriophage that lacks its proteinaceous capsid structure is also called a viroid.
False
Waterborne illness only occurs from exposure to contaminated drinking water, not from recreational use of contaminated water.
False
Coliforms in a water sample indicate ________ contamination.
Fecal
Distinguish how fermentation and respiration differ.
Fermentation forms organic acids and takes place in the absence of oxygen, while respiration forms water and carbon dioxide in the presence of oxygen.
Microbes capable of fermentation are often used in food. What is the main function of fermentation for the microbes?
Fermentation regenerates NAD+ so that glycolysis can continue.
On a global scale, the most important waterborne bacterial pathogens are _________
Vibrio cholerae and Salmonella enterica serovar Typhi
In the oceans, prokaryotes are greatly outnumbered by
Viruses
The proton motive force (PMF) is driven by __________.
the difference in charge across the plasma membrane with protons outside the membrane
During an oxidation reaction,
the donor molecule loses an electron and becomes oxidized.
When the cell is not in the presence of lactose,
the repressor proteins bind to the operator
The light reactions take place in the _________ and the Calvin cycle takes place in the _________.
thylakoids; stroma
T/F An ecosystem includes both the living organisms and abiotic materials that function together.
True
T/F Biofilm formation is more likely to occur when Vibrio cholerae is found in low densities such as sea water.
True
The lac operon is an example of ________ control in which the presence of an ________ is required for transcription to occur.
negative / inducer
Biofilm structure is determined by
Nutritional factors
Enzymes that incorporate oxygen into compounds are called _________
Oxygenases
The function of a kinase is
Phosphorylation
________ are the main primary producers in freshwater environments.
Phototrophic microorganisms
If you wanted to culture a methanogen, what would be one of the steps you would have to take?
Removing all O2 from the headspace of the culture
Why has research in metabolomics been slower than in genomics, transcriptomics, and proteomics?
Screening for metabolites is technically challenging due to their diversity.
Why are some xenobiotics biodegraded slower than crude oil and petroleum products?
Some xenobiotics are novel compounds that differ from naturally occurring chemicals, thus microorganisms have not yet evolved to effectively degrade them.
T/F Organisms in natural environments can be detected by assaying for the presence of their genes.
True
T/F Quorum sensing relies upon a large cell population which then turns on transcription.
True
At approximately what temperature are most household freezers kept?
-20
How can DNA binding proteins (DBP) regulate transcription?
-DNA-binding proteins can block transcription -DNA-binding proteins can catalyze transcription -DNA-binding proteins can activate transcription
According to the animation, where on the DNA strand does a repressor bind?
The operator
Applying your knowledge of metabolism, glycolysis starts with one molecule of glucose (6C) and produces a net total of __________.
two pyruvates; 2 NADH; 2 ATP
Compounds that are NOT produced by organisms anywhere in nature are called __________.
xenobiotic
Fluorescent in situ hybridization (FISH) can be used to determine __________.
-how many Salmonella typhimurium cells are present in a sample of unpasteurized apple juice -whether a specific piece of mRNA is being produced -the phylogenetic diversity of an environmental sample
What is thought to be the maximum temperature for life to exist?
150 C
In what year did Stanley Prusiner discover prions?
1982
Which of the following equations represents photosynthesis?
6CO2 + 6H2O → C6H12O6 + 6O2
What is the benefit for a bacteriophage to be a temperate (or lysogenic) virus?
A single infection event can produce millions of new viral particles instead of hundreds of viral particles.
To determine if you have identified a functional open reading frame (ORF), you should have ________________ within the sequence.
A start codon and ribosomal binding site (RBS)
What provides the carbon atoms that are incorporated into sugar molecules in the Calvin cycle?
Carbon dioxide (CO2)
Autotrophs are always __________.
Chemolithotrophs
The term phage is generally reserved for the viruses that infect
Bacteria
An organism living in the bottommost region of a body of water is described as being
Benthic
The microbial oxygen-consuming capacity of a water sample is called its
Biochemical oxygen demand
What components make up the structure of a virion?
Capsid and genome
Which of the pairs below are matched correctly for these clostridial pathogens involved in food poisoning?
C. perfringens: produces enterotoxin
Methanogens that make methane from CO2 and H2 have some unique coenzymes that facilitate the reduction of CO2 to form CH4. Which categories of coenzymes are required?
C1 carriers and redox electron donors
What is the correct general equation for cellular respiration?
C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP energy
What occurs at the bridge step?
Decarboxylation of pyruvic acid
Which of the following is an example of a biofilm?
Dental plaque
Denitrification contributes to global warming by __________.
Destroying ozone
A protein region with a specific function and structure is called a
Domain
Which is one major difference between anaerobic and aerobic respiration?
Electron acceptor
Which of the following statements is FALSE concerning enrichment bias?
Enrichment bias favors organisms that grow quickly.
The type of Escherichia coli that produces a verotoxin similar to the one produced by Shigella dysenteriae is ________ E. coli.
Enteroherorrhagic
Some viruses, especially animal viruses, have an envelope surrounding their nucleocapsid. This envelope may have viral proteins embedded in it. Why are the viral proteins more readily recognized and targeted by the immune system than the envelope?
Enveloped viruses are often coated with animal cell membrane as they leave the cell. This membrane is a major component of the viral envelope. The viral proteins are more readily recognized by the immune system, as they are more distinct from the materials normally found in and on the cells. However, the envelope can contain several types of viral components as well.
In the developed countries of the world, most intestinal infections are transmitted via
Food
Illness that results from ingestion of pathogen-contaminated food is __________.
Food infection
Based on the animation, how many electron carriers are reduced in the Krebs cycle only?
Four
Which operons are never transcribed unless activated?
Inducible operons
According to the animation, how do the repressor proteins block the transcription of the structural genes?
It binds to the operator when activated.
T/F Organisms that degrade hydrocarbons in crude oil are ubiquitous in the environment and have evolved special strategies, such as surfactant production, that allow them to readily use hydrocarbons as electron donors and carbon sources.
TRue
Which statement describes the difference between the normal neuron protein PrPC and the pathogenic version PrPSc?
The amino acid sequence is identical, but the three-dimensional conformation is different.
How do viability stains usually distinguish between living cells and dead cells?
The dye specifically targets intact cytoplasmic membranes
What would be the most likely effect of a mutation in the operator of a lac operon?
The genes would be constitutively expressed
With which genetic region does the repressor protein interact?
The operator region
What is the driving force of energy production in steps 6 and 7?
The oxidation of three-carbon compounds.
According to the animation, to what genetic element does the RNA polymerase bind?
The promoter
Which of the following genetic elements is transcribed into a single mRNA?
The structural genes
How is anaerobic respiration different from aerobic respiration?
The terminal electron acceptor in anaerobic respiration is not oxygen.
Chlorophyll and bacteriochlorophyll pigment molecules absorb light energy for photosynthesis. Each specific version of these molecules absorbs a different range of wavelengths of light, allowing different species of phototrophs to coexist by partitioning their use of the light spectrum. What controls the absorption spectrum of each particular chlorophyll/bacteriochlorophyll?
The various substituents on the tetrapyrrole ring alter the absorption properties of the pigments.
Which of the following describes a retrovirus?
The virus uses reverse transcriptase to make DNA from an RNA template, the reverse of the normal process of gene expression.
What is the fate of metabolites during respiration?
They are oxidized completely to carbon dioxide and water.
How are prions different from other infectious agents?
They lack nucleic acid
How are viruses different from cells?
They require a host in order to reproduce
Which statement describes the citric acid cycle?
This process produces some ATP and carbon dioxide in the mitochondrion.
Which statement describes glycolysis?
This process splits glucose in half and produces 2 ATPs for each glucose.
By isolating total community RNA, using reverse transcriptase to make cDNA copies of it, and then sequencing the cDNA, ecologists can __________.
determine the community genome expression at the moment of sampling
What structure can the viral genome take?
ds-DNA, ss-DNA, ds-RNA
What is the medium used in the membrane filter (MF) procedure to differentiate fecal coliforms and Escherichia coli?
eosin-methylene blue agar (EMB) blood agar triple sugar iron agar
If ΔG0 is negative, the reaction is
exergonic and energy will be released
For microbial biodiversity studies, it is common to identify the ________ rather than the ________ as a measure of biodiversity.
genes / organisms themselves
Which of the following processes takes place in the cytosol of a eukaryotic cell?
glycolysis
Staphylococcus aureus is a common causative agent of foodborne disease because it
grows on many foods, is present in some humans that work in food processing, and produces several heat-stable enterotoxins.
In microbial ecology studies, the FISH technique identifies organisms based on
hybridization of a fluorescent probe to specific ribosomal RNA sequences.
Nearly 90% of all foodborne illnesses are associated with __________.
norovirus, Salmonella, Clostridium perfringens, and Campylobacter jejuni
As a microbiologist, you have been asked to advise a town council on the possible ways to remove PCB contaminants from the local groundwater. Which microbial process is most likely to have bioremediation potential in this case?
reductive dechlorination
Activation energy is the energy
required for a chemical reaction to begin.
Metagenomics involves the analysis of a microbial community by __________.
sampling and sequencing all of the genes in an environment
Enrichment cultures are often effective for isolating bacteria from complex communities in natural samples because they __________.
select both for and against certain bacteria
The Baltimore Scheme to classify viruses contains a total of ________ groups based on ________.
seven / genome composition and transcription mechanism
Synthetic plastics are
slower to degrade than microbial plastics.
Where would you expect to find electron transport chains in a prokaryote?
Along the plasma membrane
Global regulatory systems include all of the following EXCEPT
Amino acid synthesis
What connects the two photosystems in the light reactions?
An electron transport chain
The abundance of cyanobacterial mats has greatly declined due to the evolution of
Animal grazers
Which of the following are the hosts for most enveloped viruses?
Animals
In which of the following organelles does photosynthesis take place?
Chloroplast
Gram-negative, rod-shaped bacteria that are facultative anaerobes, are non-spore formers, and ferment lactose to acid and gas are __________.
Coliforms
The most common route of transmission of Salmonella enterica typhi worldwide is through
Contaminated water
Which U.S. government agency monitors water utility reports?
Environmental Protection Agency
Which bacteria involved in food infections produce toxins to cause host damage?
Escherichia coli and Salmonella
Food that is heavily salted or candied does not need to be refrigerated. Why not?
Extremely concentrated solutions are very hypertonic and therefore desiccate microorganisms. As a result, there is no need for lower temperatures through refrigeration to slow growth.
Psychrotolerant microorganisms can survive and grow at
Refrigeration temperatures
In Bacteria, sensor kinases that respond to extracellular signals transfer this signal to the cytoplasmic machinery by typically phosphorylating the residues.
Histidine
Tests to monitor water safety often report the number of fecal coliform bacteria found in samples. Which of the following statements accurately reflects water safety recommendations based upon fecal coliform levels?
If the level of fecal coliform bacteria is low, the likelihood of fecal contamination is low, but the water may still be unsafe because of the presence of other pathogens.
Differentiate between persistent and latent animal virus infections.
In a persistent infection, the host cell is continually releasing new viral particles slowly. In a latent infection, there are periods of time where the virus is not replicating and creating new viral particles.
When is the repressor protein transcribed?
It is always transribed
Which of the following statements about fermentation is true?
It is an alternative way to return electron carriers to their oxidized state.
What is the fate of the NAD+ newly regenerated by fermentation?
It returns to glycolysis to pick up more electrons.
What is the role of pyruvic acid in fermentation?
It takes the electrons from NADH, oxidizing it back into NAD+.
Which of the following is an acid produced by fermentation?
Lactic acid and propionic acid
In the lac operon, which of the following conditions would allow the structural genes to be transcribed?
Lactose is present and glucose is absent.
A virus that kills its host is said to be
Lytic or virulent
Transcriptional regulators bind most frequently at the ________ site of DNA.
Major groove
From the aquatic systems below, where are heterotrophic Bacteria the most abundant?
Marine coastal waters
The most common source of Escherichia spp. food poisoning is contaminated
Meat
The total genetic complement of all cells within a microbial community is called a(n)
Metagenome
Explain why viroids can only infect and damage plant cells, but not animal cells.
Plant cells contain a RNA polymerase that can copy RNA can animal cells do not.
Microbial plastics are composed of
Polyhydroxyalkanoates (PAHs)
Which of the following represents increasing microbial diversity?
Population -guild- community
Clostridium botulinum is a gram-________ rod that produces an ________.
Positive endospore-forming/ exotoxin
Of the following examples, which is not a common part of many viral life cycles?
Pox viruses replicate in the cytoplasm of the cell
Two major environmental extremes of the deep sea are high ________ and low ________.
Pressure/ nutrient levels
What is meant by substrate-level phosphorylation?
Production of ATP by transferring phosphates directly from metabolic products to ADP
From which phrase is the term "prions" derived?
Proteinaceous infectious particles
According to bacterial abundance studies done so far on soils, the ________ represent the most abundant phylum.
Proteobacteria
When the cell is NOT in the presence of tryptophan,
RNA polymerase can transcribe mRNA
Viruses rely on the host cell machinery to make new viruses, but they sometimes provide their own enzymes (such as reverse transcriptase, which is an RNA-dependent DNA polymerase). Which of the following types of enzymes would a virus need to provide in order to replicate within a cell? In other words, which of these enzymes would not normally be found in a cell unless a virus provided it?
RNA replicases (RNA-dependent RNA polymerases) for RNA viruses
Which statement is TRUE?
RNA viruses contain their own nucleic acid polymerases
Which of the following statements regarding redox reactions is true?
Redox reactions involve an oxidation reaction coupled with a reduction reaction.
If an organism used glycolysis (Embden-Meyerhof-Parnas pathway) to break down glucose and produce ATP but was unable to subsequently use fermentation or an electron transport chain (respiration), what problem would develop?
The available NAD+ would be converted to NADH and glycolysis would eventually stop due to the lack of NAD+.
Two-component regulatory systems rely on a balance of phosphorylation and dephosphorylation of sensor kinases and response regulators. If the response regulator became permanently phosphorylated due to lack of phosphatase activity, which of the following would NOT happen?
The cell would become more sensitive to the environment stimulus.
Why is reduction the term used to describe the gain of an electron?
The electron acceptor's net charge decreases.
Which statement is TRUE about the fluid from the hydrothermal vents?
The fluid contains large amounts of reduced inorganic materials.
Which statement describes the electron transport chain?
This process uses energy captured from electrons flowing to oxygen to produce most of the ATPs in cellular respiration.
What is the basic function of the lac operon?
To code for enzymes involved in catabolizing lactose
What is the overall function of the trp operon?
To ensure that the cell has a supply of tryptophan at all times
What is the function of the structural elements of a virus?
To package and protect the viral genome
Reheating food to a temperature sufficient to kill bacteria is helpful in making food safer. However, is there a way that one can get food poisoning despite food having been reheated?
Toxins may be heat-stable above temperatures that kill bacteria.
One reason that regulation of gene expression is important is that it saves energy and materials from being used when they are not needed. Although most genes have more than one form of regulation acting upon them, at which point would regulation be most efficient in conserving energy and materials if the product of a gene is not needed?
Transcriptional regulation (regulation of whether transcription occurs)
Most riboswitches control
Translation
How does the proton motive force lead to production of ATP?
Translocation of three to four protons drives the F0 component of ATPase which in turn phosphorylates one ADP into ATP.
The most important potential common source of infectious disease is
Water
Pickling is a type of food preservation utilizing
Weak acids
Which of the following examples describes a type of catabolite repression?
When glucose is present, the lac operon is inhibited.
Why would using nitrogenous fertilizer near a body of water affect the organisms in the body of water?
When runoff enters the body of water, the nitrogen level significantly increases, which increases the activity of the microorganism there and upsets the balance of the ecosystem.
A patient reported a headache, chills, vomiting, and diarrhea that occurred 12 hours after having a meal at home that included chicken. The physician suspected which type of organism?
a food infection, most likely Salmonella
A reaction that involves the transfer of electrons from one molecule to another is referred to as
a redox reaction
The function of NAD+/NADH in the cell is best described as __________.
a way to increase the types of redox reactions that occur in the cell by acting as an intermediary between dissimilar compounds
Winogradsky columns are used primarily for enrichment of
aerobes, anaerobes, and phototrophs.
Human influences on the carbon cycle may cause major upsets in the balance of the ecosystem because __________.
increasing the anthropogenic carbon dioxide released in the atmosphere may significantly decrease the amount of calcium carbonate in the deep ocean
The phylogenetic diversity analysis of complex microbial communities often targets small subunit (SSU) ribosomal RNA genes. This is because rRNA is found in all organisms and __________.
is highly conserved over evolutionary time
Transcriptome analysis is useful in relation to genome analysis because
it analyzes RNA, thus it reveals which genes are expressed under different conditions.
The pH of most foods is
Neutral or acidic
Ecological theory states that for every organism there is at LEAST one ________, and the microenvironment where the organism is most successful is called the ________.
Nice/ prime niche
In anoxic environments, organic compounds are cycled back to carbon dioxide and methane by __________.
Fermentation
Many nutrient cycles are coupled and changes in one cycle will affect another. This means that a change in the amount of carbon dioxide fixed is intimately affected by the amount of __________.
Nitrogen available in an ecosystem
The most common source of individual foodborne botulism outbreaks are due to consumption of
Nonacid, home-canned vegetables
Which step is the step for which glycolysis is named?
Fourth
Gluconeogenesis is the process of synthesizing __________.
Glucose from other compounds
When arginine is added to a culture already growing exponentially in a medium without arginine, what occurs?
Growth continues, but the production of enzymes required for the synthesis of arginine ceases.
What provides electrons for the light reactions?
H20
In what organelle would you find acetyl CoA formation, the citric acid cycle, and the electron transport chain?
Mitochondrion
Which organelle is the primary site of ATP synthesis in eukaryotic cells?
Mitochondrion
Glycolysis produces energy in which form?
NADH and ATP
According to the animation, which compounds provide electrons to the system?
NADH and FADH2
What transports electrons from the light reactions to the Calvin cycle?
NADPH
Plaque assays are often used to estimate the number of virions in a sample of a particular volume (the titer). The count is given as plaque-forming units. Which of the following is NOT generally a concern that must be considered in evaluating the results of plaque assays? View Available Hint(s)
NOT: The largest problem is that single viruses may create multiple plaques, resulting in overestimates of the number of viruses present.
Which of the following is NOT a way in which viruses are different from living organisms?
NOT: Viruses are obligate parasites and no living organisms are obligate parasites. TRUE: Viruses have DNA or RNA, not both -Viruses are acellular and all living things are made up of cells -Viruses depend on their host to synthesize the essential components of new viruses (e.g., genetic material and proteins), while living organisms are capable of synthesizing these components even if they require a host for food, shelter, or other necessities.
Some viruses are associated with cancer. There are a variety of ways in which viruses may affect a cell in a way that may lead to the formation of a tumor. Based on your knowledge of the life cycles of viruses and of molecular genetics, what is one way that this might happen?
Viral genetic material inserts into a host genome, placing a promoter in a new location and turning on a gene that had previously been turned off.
The role of an enzyme includes all EXCEPT which of the following?
reducing the rate of a reaction to allow for better control