Microbiology test 2
The generation time of Mycobacterium tuberculosis is ______.
12 hours
During one cycle, the sodium-potassium pump binds and moves _______.
3 Na+ and 2 K+
Using the equation Nf = Ni (2n), determine how many Staphylococcus aureus cells are present in a custard tart under these circumstances. During preparation, 15 cells were deposited in the custard, and the tart has sat at room temperature for 5 hours. S. aureus has a generation time of 20 minutes.
4.9 x 10 to the 5 cells
Consider the following hypothetical conditions: A population of 10,000 bacteria has a doubling time of 20 minutes under a given set of growth conditions. The culture is allowed to grow for 2 hours. Select the number of bacteria that best predicts the population size at the end of the two hour incubation period. Assume there is no lag phase.
640,000
How many generations does it take for a single bacterial cell to become 256?
8
If an organism lost the ability to make primase, what would it be unable to do?
Add a short sequence of complementary RNA to the existing DNA strand
Select the statement that best describes the antimicrobial activity of chlorhexidine.
Chlorhexidine targets cell membrane components and denatures proteins.
An operon is composed of ______.
DNA
Which of the following best describes transcription?
DNA - RNA
Responsible for removing the primer, closing gaps in the DNA and repairing mismatched bases
DNA polymerase I
Responsible for adding bases to the new DNA chain and proofreading the newly laid down bases
DNA polymerase III
The lac operon system, first described by Jacob and Monod, regulates lactose metabolism in
E. coli
Ultraviolet water treatment systems are very common in _______ but not in the United States.
Europe
___ is now able to bind to the promoter, transcribing all three structural genes needed for lactose catabolism.
RNA polymerase
Before the lagging strand can begin assembling new DNA nucleotides, which of the following must occur?
RNA primase contracts a short RNA primer
Which of the following statements are not true about the sodium-potassium pump?
The ions in the extracellular fluid bind to the carrier protein, and the potassium attached to the carrier protein is released.
Select all statements that describe features of transcription and translation found in eukaryotes but not in bacteria.
Transcription and translation both occur in the cytoplasm. Transcription and translation both occur in the cytoplasm. A tail of multiple adenine ribonucleotides is added to the mRNA transcript. The mRNA transcript must pass through pores to get out of the nucleus. RNA transcript is processed to remove introns and splice together exons.
choose the statement that correctly explains how an antibiotic that inhibits protein synthesis can be selective
antibiotics bind to the 70S bacterial ribosomes but not to the 80S eukaryotic ribosomes
Destruction of most microbial life on living tissue
antisepsis
Which type of microbes were first found to utilize the lac operon in order to conserve energy by only expressing genes when the gene products were needed?
bacteria
Most bacteria increase their numbers by _____.
binary fission
What is the source of energy used to power the sodium-potassium pump?
breakdown of ATP
Cryptosporidium produces diarrhea that is self-limiting in healthy individuals, but in _______ patients, it can produce dehydration through severe diarrhea and can be life-threatening.
elderly, infant, and immunocompromised
Choose the phase of the bacterial growth curve during which a bacterial population has the shortest doubling time.
exponential growth phase
Phase during which cells are growing very quickly, at their maximum rate of cell division
exponential growth phase
Describes an organism that grows optimally at temperatures ranging from 80°C to 120°C
extreme thermophile
Describes an organism that can grow in the presence of oxygen and can detoxify it, but can also grow in the absence of oxygen
facultative anaerobe
An effective antimicrobial drug will only destroy 30% of the host's cells.
false
Desiccation is a form of physical control of microorganisms that can be used in moist or dry forms.
false
Drugs that block quorum-sensing pathways among bacterial cells have unfortunately been ineffective thus far in treating biofilm infections.
false
Nonionizing radiation exhibits good penetrating power and can be used for cold sterilization.
false
One DNA strand is used as the template to make two new strands of DNA.
false
Polymyxin drugs are very broad-spectrum antibiotics that exhibit high selective toxicity.
false
True or false: Chlorine treatment is effective in removing Cryptosporidium from water.
false
True or false: The cell can replicate and transcribe DNA with thymine dimers.
false
a narrow spectrum antimicrobial would be an appropriate choice to treat an abscess caused by several different microbe species, including both gram-negative and gram-positive bacteria
false
many antibiotic drugs exhibit a high level of selective toxicity because the structure targeted by the drug is common to both the infectious agents and the host
false
Choose the microbial control method that neither inhibits nor kills microbes, but instead physically removes them from liquids or air.
filtration
The most versatile method for sterilizing heat-sensitive liquids is _______.
filtration
A mutation resulting from an insertion or deletion of bases that causes a change in the reading frame of the mRNA
frameshift mutation
The sum total of the genetic material of a cell is its ______.
genome
The genetic makeup of an organism is referred to as its ________ whereas the observable traits due to gene expression are referred to as its __________.
genotype; phenotype
Early in the process of DNA replication, the enzyme ______ separates the two strands.
helicase
Responsible for unzipping the DNA helix
helicase
what most accurately reflects characteristics of fluoroquinolone drugs
levofloxacin is. third-generation fluoroquinolone used in cases of resistant bacterial infections
Responsible for the final binding of nicks in DNA during replication
ligase
Photolyase repairs thymine dimers in a _______ dependent manner.
light
a cell exposed to a hypertonic environment will __ by osmosis
lose water
Carbon, nitrogen, oxygen and hydrogen are considered _______ because they are required in relatively large quantities, whereas manganese, zinc, and copper are considered ______ because they are required in very small quantities.
macronutrients; micronutrients
Describes an organism that grows optimally at temperatures ranging from 20°C to 40°C
mesophile
A majority of medically important microbes are classified as ______
mesophiles
effective against penicillinase-producing bacteria
methicillin
select the correct pairing of an anti fungal drug and its applicaiton
miconazole, vaginal infections
Describes an organism that can't grow at normal atmospheric oxygen concentrations, but does require a small amount of oxygen for growth
microaerophile
A mutation which results in a change in a codon such that a different amino acid is specified
missense mutation
Simple diffusion is defined as the movement of _______.
molecules from areas of higher concentration to areas of lower concentration
Two organisms living together in which both pa
mutualism
The letters of an mRNA codon are based on the ______ in the nucleotides of the transcript.
nitrogenous bases
Excision repair, which is used to correct thymine dimers, requires ________. high temperatures low pH light none of the choices are correct
none of the choices are correct
A mutation which changes a codon that specifies an amino acid to a stop codon, resulting in premature termination of polypeptide synthesis
nonsense mutation
The fluoroquinolones, or quinolone drugs, are a group of antimicrobials that inhibit _______.
nucleic acid structure and/or function
Describes an organism which requires oxygen for growth and has the enzymes to remove toxic by-products of oxygen metabolism
obligate aerobe
Describes an organism that is unable to use oxygen and lacks the enzymes to detoxify oxygen, thus requiring the absence of oxygen for growth
obligate anaerobe
What term describes an organism that lacks superoxide dismutase and catalase enzymes?
obligate anaerobe
If lactose is present, the operator of the lac operon is switched ______; therefore, this is an example of a/an ______ operon.
on; inducible
The specific point on the DNA molecule where replication begins is the ______.
origin of replication
The ___ is composed of a gene encoding a ___ protein that normally keeps this operon in the __ position.
regulator; repressor; off
The protein that promotes translation termination is called _______.
release factor
DNA polymerase _______.
requires a template for the synthesis of DNA
New research has shown that various regulatory RNAs can alter gene function. Examples of such regulatory RNAs are ______.
riboswtiches
Select the type of antibiotic that is used to treat cases of tuberculosis, due to its ability to more specifically target bacterial RNA polymerase than the eukaryotic form of the enzyme.
rifamycin
the feature of an antimicrobial that allows it to kill or inhibit microbes yet be harmless to the host is referred to as
selective toxicity
DNA replication is described as ______.
semiconservative
A red blood cell placed in a hypertonic medium will ______.
shrink
A mutation that changes one codon to a different codon that specifies the same amino acid, such that there is no change in the resulting polypeptide
silent mutation
The property of wobble means that ______ mutations result if changes occur in ______ position of some codons.
silent; the third
Used in an ointment on 2nd and 3rddegree burns
silve sulfadiazine
Topical germicide on mouth ulcers and root canals
silver nitrate
Disinfection procedures must take into account _________.
the mixture of microbes being targeted whether the microbes in biofilms are dispersed the amount of organic matter associated with the microbes
Treating malarial infections is theoretically difficult because ______.
the protozoal parasite is eukaryotic and therefore similar to human cells there are several species of Plasmodium no single drug can target all the life stages of Plasmodium
Two different mechanisms for copying the DNA strands are used because _______.
the strands are oriented in opposite directions
the ratio of the toxic does of an antimicrobial drug (that is toxic to humans) to its minimum therapeutic does is the
therapeutic index
Describes an organism that grows optimally at temperatures ranging from 45°C to 80°C
thermophile
Choose the statement that identifies the major disadvantage of both cold and desiccation in terms of microbial control.
these methods are bacteriostatic rather than bactericidal
select the statement that most accurately reflects biofilms
they are associated with chronic ear infections
Responsible for supercoiling and untangling of DNA
topoisomerase I and II
Select the most disadvantageous characteristic(s) of phenolics.
toxicity and resistance
Direct damage to tissue or an organ due to the effect of an antimicrobial on that tissue or organ is known as drug ______, whereas an inappropriate immune reaction to an antimicrobial is known as drug-induced _______.
toxicity; allergy
After DNA replication, two identical DNA molecules are formed
true
All structural genes in an operon code for proteins related to the same function.
true
Azidothymidine, or AZT, is a drug used in the treatment of HIV infection that exhibits a high degree of selective toxicity.
true
Cryptosporidium was able to evade or resist filtration and chlorination of the spray park's water supply.
true
Mutations are the primary source of genetic variation that makes evolution possible.
true
Recombinant organisms often exhibit new traits, such as antibiotic resistance or novel metabolic capabilities.
true
Several codons can be translated into the same amino acid, but one particular codon cannot be translated into different amino acids.
true
The amino acid sequence of a protein determines its shape and specific function.
true
environmental microbes are now recognized as important reservoirs of antimicrobial resistance genes
true
Osmosis is best defined as the movement of _______.
water molecules across a membrane from an area of high water concentration to an area of lower concentration
What was the most likely mode of transmission of Cryptosporidiumat the Seneca Lake State Park Sprayground?
water-borne
carrier-mediated transport group translocation phagocytosis pinocytosis
active transport
Describes an organism that does not use oxygen, but can grow to a limited extent in the presence of oxygen
aerotolerant anaerobe
UV water treatment systems are effective in treating ________. protozoans bacteria viruses all of these choices are correct
all of these choices are correct
brand spectrum drug, used against gram-negative enteric bacteria
ampicillin
A competitive relationship between free-living organisms in which one organism secretes substances that are toxic to the other in order to acquire more space or nutrients for itself
antagonism
antibiosis is a form of __-
antagonism
the antibiotics listed here all have similar minimum inhibitory concentrations. choose the antibiotic that would be the best option for treatment
antibiotic Y therapeutic index = 100
pick the true statement about antibiotics
antibiotics are natural products of microorganisms
Which of the following statements are not true about the sodium potassium pump?
ATP is broken down into ADP and potassium to supply the energy.
How does UV radiation damage DNA?
It causes covalent bond formation between adjacent thymine bases.
Which of the following statements about tRNA is true?
No tRNA can recognize a stop codon.
If RNA polymerase was reading a segment of DNA with the sequence AGGCGTA, what order of nucleotides would be added to the mRNA transcript?
UCCGCAU
Transcription is targeted most directly by ______.
UV radiaiton
What type of radiation in sunlight causes damage to DNA?
UV radiation
Select all of the agents that will kill a microbial pathogen or completely inactivate its ability to cause disease.
Virucide, germicide, sporicide
Translation is terminated when a stop codon is presented at the _______.
a site
Select the term that refers to a microbe able to survive very low pH conditions.
acidophile
The sodium-potassium exchange pump is an example of ______.
active transport
The cell can no longer regulate the passage of materials in and out of the cell. Which of the four main targets is affected in this scenario?
cell membrane
A drug destroys the peptidoglycan molecules of a bacterial cell. Which of the four main targets is affected in this scenario?
cell wall
Select the major cellular targets of physical and chemical control agents. Check all that apply.
cell wall, cell membrane, proteins
Thymine dimers are formed in DNA, preventing replication. Which of the four main targets is affected in this scenario?
cellular synthesis
which of the following represents a correct pairing of an antimicrobial drug and its cellular target?
cephalosporins-- cell wall
An organism which requires simple inorganic chemicals as its energy source and carbon dioxide as its carbon source
chemoautotroph
in terms of energy and carbon sources, deep-sea vent microorganisms and methanogens are most specifically classified as ___
chemoautotrophs
An organism which requires organic compounds as both its energy and carbon source
chemoheterotroph
added to penicillins to inhibit beta-lactamases
clavulanic acid
Two organisms living together in which one organism is benefited and the other is neither benefited nor harmed
commensalism
Within the ___, the repressor binds to the ____ blocking transcription of structural genes needed for lactose metabolism.
control locus; operator
In a viable count, each _______ represents a _______ from the sample population. f
cooling; CFU
The structure that divides the bacterial cell in two is termed the ______.
cross septum
What organism was the cause of the outbreak at the Seneca Lake Sprayground?
cryptosporidium
Nutrient depletion and waste accumulation prevent cell growth and cells die exponentially
death phase
Mechanical removal of most microbes from living or inanimate surfaces
decontamination
Destruction of most microbial life on inanimate surfaces
disinfection
The time required for one complete cycle of binary fission is known as the ______, or generation time.
doubling
Select all of the food items where microbial growth is controlled by means of osmotic pressure.
honey, salt-cured meats, apple cider, milk. yogurt, jellies
net diffusion of water is out of the cell
hypertonic condition
A cell in this environment will lose water and shrink as water moves out of the cell by osmosis.
hypertonic environment
net diffusion of water is into the cell
hypotonic condition
A cell in this environment will swell as water moves in by osmosis and may lyse if it does not have a cell wall.
hypotonic environment
DNA polymerase adds new nucleotides _______
in the direction toward the replication fork on the leading strand
rates of diffusion are equal in both directions
isotonic condition
a cell in this environment will neither shrink nor swell as there is no net movement of water into or out of the cell by osmosis
isotonic environment
UV irradiation inactivates Cryptosporidium because _______.
it leads to a blocking of the action of DNA polymerase and RNA polymerase Correct
Select the advantages of glutaraldehyde as an antimicrobial agent. Check all that apply.
it remains effective in the presence of organic matter it is non-corrosive it is a chemical sterilant and high level disinfectant
Choose the method of antimicrobial susceptibility testing that involves measuring and evaluating zones of inhibition around antibiotic disks placed on a culture of bacteria prior to incubation.
kirby-bauer test
When ___ is added to a cell's environment, it binds the repressor freeing the operator segment of the DNA.
lactose
Adjustment period during which cells are dividing slowly while they adjust to growth conditions
lag phase
Two organisms living together in which one organism is benefited and the other (the host) is harmed
parasitism
simple diffusion facilitated diffusion
passive transport
generally most effective against gram-positive bacteria
penicillin G and Pencillin V
drugs that prevent the formation of the bacterial cell wall are
penicillins
An organism that can synthesize all its required organic components from CO2 using energy from the sun is a _______.
photo autotroph
An organism which requires light as its energy source and carbon dioxide as its carbon source
photo autotroph
An organism which requires light as its energy source and organic compounds as its carbon source
photoheterotroph
R factors are _______ that contain a code for _______.
plasmids; drug resistance
Select the applications of ethylene oxide sterilization. Check all that apply.
plastics prepackaged medical devices bacterial growth media milk and dairy products
What strategy involves the use of nutrients to directly encourage the growth of existing healthy biota?
prebiotics
Responsible for synthesizing an RNA primer
primase
The two microbial forms most resistant to chemical and physical control measures are _______ or proteinaceous infectious particles, and ______ produced by Bacillus and Clostridiumspecies.
prions; endospores
The native state of certain enzymes are destroyed by heat, and the active sites are no longer able to bind with substrate. Which of the four main targets is affected in this scenario?
proteins
What type of organism caused the outbreak at Seneca Lake Sprayground?
protozoan
Describes an organism that grows optimally at temperatures ranging from 0°C to 15°C
psychrophile
Describes an organism that has an optimum growth temperature between 15°C and 30°C, but is able to grow slowly at colder temperatures
psychrotolerant
Incorporated into urinary catheters
pure silver ions
Which of the following will pass through a cell membrane most easily?
small non polar molecules
The sodium-potassium pump functions to pump _______.
sodium ions out of the cell and potassium ions into the cell
phase during with nutrient depletion and accumulation of wastes begin to slow cell growth such that the rate of cell increase equals the rate of cell death
stationary growth phase
Select the methods that illustrate the use of moist heat to control microbes. Check all that apply.
steam autoclave, pasteurization, boiling water
cell enlarges and the chromosome is replicated a transverse septum grows inward as the two chromosomes are pulled towards opposite ends of the elongating cell septum is completed daughter cells are separated or may remain attached
steps of binary fission
Destruction of all microbial life
sterilization
Which part(s) of an operon will eventually be translated to protein?
structural genes
When lactose again becomes depleted in the cell, the repressor binds to the operator blocking additional synthesis of enzymes from the ____
structural locus
A relationship in which free-living organisms cooperate and share nutrients
synergism
The rate of diffusion is affected by which of the following?
temperature, size of molecules, and steepness of the concentration gradient
When sugar is mixed with water, equilibrium is reached when _______.
the dissolved sugar molecules are evenly distributed throughout the solution
