Microbiology 20 Chapter 6
A total of 145 colonies were counted on the plate that received 1.0 mL of the 1:10,000 dilution of a specimen. What is the bacterial count for the original specimen?
1,450,000 CFUs/mL
By one estimate, viruses outnumber bacteria by which factor?
10
What incubation temperature is preferred for the growth of most medically important bacteria? (Select all that apply)
37°C, 45°C, and 98°F
A poiliovirus-infected cell can release how many virions?
About 100,000
Diagnostically, if cytopathic effects are seen, what does this indicate?
Active viral infection
Host cells of viruses include
All of these choices are correct.
Uncoating of viral nucleic acid
All of these choices are correct.
Most enveloped viruses are which of the following?
Animal viruses
Identify all of the components of a nucleocapsid.
Capsid and Nucleic acid
At minimum, viruses are composed of which of the following?
Capsid and nucleic acid
Which of the following relate to all viruses?
Capsid, Acellular, and Nucleic acid
Which of the following is the monomeric unit for a viral capsid?
Capsomer
Which is a simple translation of cytopathic?
Cell disease
Reovirus
Cell enlargement
Poliovirus
Cell lysis
Which type of capsids are composed of multiple protein types and nonsymmetrical shapes?
Complex
Which types of viruses are released by budding?
Enveloped viruses
A megavirus is considered to be smaller than 22 nm.
False
Viral replication follows essentially the same steps as replication of a prokaryotic cell.
False
Virus are classified into species based on whether they can reproduce to produce fertile offspring, much like plants and animals.
False
Measles virus
Formation of syncytia
Process of adding a microbe to a growth material
Inoculation
What is true concerning the viral envelope?
It contains viral proteins. and It was once a part of the host cell.
Rabies virus
No change in cell shape
Cultures of a bacterial species were incubated on the shelf of a refrigerator, out on a lab bench top, on the shelf of a 37°C incubator, and on the shelf of a 50°C incubator. After incubation, there was no growth at 37°C and 50°C, slight growth out on the bench top, and abundant growth at refrigeration. What term could be used for this species?
Psychrophile
The type of culture most frequently used in the laboratory which contains only a single species of microbe.
Pure culture
Influenza
Rounding up of cells
Which of the following are true about viral envelopes?
They are composed of host membrane., They can contain host-encoded proteins., They can contain virus-encoded proteins., and They are important for binding to host cells.
What is common to replicase and reverse transcriptase?
They are preformed viral proteins.
Why must living cells carry a larger genome than viruses?
They must be able to carry out metabolic processes that sustain independent life.
Viral evolution theory states that viruses arose from loose strands of genetic material.
True
Viral nucleic acid enters the host cell and uses host cell's replication and synthesis machinery in order to produce new nucleic acid molecules, proteins for the capsid, spikes, and viral enzymes.
True
Viral replication can involve the copying of RNA in an RNA virus.
True
Which term best describes viruses?
Ultramicroscopic
Which term describes the process of a virus losing its capsid and exposing viral nucleic acids to the immediate environment?
Uncoating
Indicate which of the following are important considerations when using the spectrophotometer to determine absorbance of bacterial cultures.
Use a cuvette of sterile nutrient broth that is the same as the one used for the bacterial culture to zero the absorbance., Be sure to properly align the cuvette each time in cuvette holder., Handle only the top of the cuvette and carefully wipe the cuvette with Kimwipes to remove any smudges., and Shut the cuvette holder cover whenever reading absorbance or transmittance.
You have a nutrient broth, an agar slant, and an agar plate with bacterial growth in or on each. If you wanted to evaluate the macroscopic appearance of the bacteria growing in or on the medium, which of the cultures would be the best choice?
agar plate
What type of medium provides the best opportunity for growing and observing the morphology of isolated colonies?
agar plates
Which types of culture media are solid? (Select all that apply)
agar plates and slants
Helical
capsid with rod-shaped capsomers that bind together to resemble a bracelet
The genetic core of every virus particle always contains
either DNA or RNA.
When a virus is noninfectious it is termed __________.
inactive
Why couldn't the avian influenza outbreak be stopped in 2015?
migratory birds repeatedly introduced the virus into healthy flocks.
An organism that cannot grow without oxygen is a/an Multiple Choice
obligate aerobe.
The type of photosynthesis that does not produce oxygen
occurs in purple and green sulfur bacteria.
Where should the label be placed on Petri dishes?
on the bottom
__________ viruses can infect host cells and later lead to cancer.
oncogenic
The capsomers are unit compositions of
protein.
An indirect method of estimating bacterial numbers is based on the turbidity of the sample. A ________ can be used to determine the turbidity by measuring absorbance.
spectrophotometer
Please choose the answer that best completes the blanks of this sentence in the correct order. The ________ plate method involves spreading an inoculum onto the surface of a plate in a pattern that results in isolated colonies in some areas of the plate after incubation, whereas the ________ plate method involves diluting an inoculum into several melted agar tubes and then adding their contents into plates for solidification and incubation.
streak; pour
Antigenic shift is a direct consequence of
the influenza virus carrying its genetic information on separate strands of RNA.
The nucleocapsid is composed of
the nucleic acid along with the capsid.
An inoculating loop or needle is sterilized in a flame or incinerator
until the entire wire is bright red.
The term autotroph refers to an organism that
uses CO2 for its carbon source.
Archaea as a group are not pathogens. This is because
mammalian hosts do not meet their environmental requirements.
"Asian" influenza viruses are found in the United States primarily because
migratory birds transmit the virus to domestic flocks.
The term heterotroph refers to an organism that
must obtain organic compounds for its carbon needs.
Viruses that consist of only a nucleocapsid are considered
naked viruses.
The severity of symptoms of a specific strain of influenza often correlates to how deeply the virus penetrates the respiratory tract. The viral component most responsible for this aspect of infection would be the _____.
neuraminidase spikes
Together the viral capsid and nucleic core is referred to as the
nucleocapsid
Together, the capsid and the nucleic acid are referred to as the __________.
nucleocapsid
All viruses
possess a capsid composed of protein. and are reliant on a host cell for their own reproduction
Which of the following methods can be used to generate isolated colonies? Select all that apply.
quadrant streak plate method, pour plate method, and dilution series plating
The "H" and "N" designations for influenza viruses refer to
receptor spikes.
A microaerophile
requires a small amount of oxygen but won't grow at normal atmospheric levels.
All of the following are characteristics of viral categorization except
ribosome shape.
Organisms that feed on dead organisms for nutrients are called
saprobes.
What data or achievement was instrumental to the initial characterization of viruses?
the discovery that infectious fluid remained infectious even when passed through a filter designed to trap bacteria
Feline leukemia virus may be lethal to cats but does not infect humans. This is a reflection of
the host range of feline leukemia virus.
A microorganism that has an optimum growth temperature of 37°C, but can survive short exposure to high temperatures is called
thermoduric.
Icosahedral
three-dimensional, 20-sided capsid with twelve evenly-spaced corners
The special affinity that a virus has for a particular type of tissue is called a __________.
tropism
Please select the characteristics that are used to identify and name viruses.
type of capsid, type of envelope, nucleic acid strand number, and area of the host cell in which the virus multiplies
Microorganisms are found in nearly every environment and are said to be
ubiquitous.
synthesis
under control of viral genes, the host cell synthesizes all the components needed to assemble new viral particles
uncoating
vesicle membrane and viral envelope fuse, releasing capsid into the host cytoplasm
assembly
viral nucleic acid encased in capsid, viral proteins inserted in host cell membrane
Fully formed viral particles capable of establishing infection in a new host are called __________.
virions
adsorption
virus attaches to its host cell by binding cell surface receptors
penetration
virus is engulfed in a vesicle or endosome and transported internally
Which of the following conditions may increase the level of microbial contamination in an environment? (Select all that apply)
warm temperature (25°-40°C), moisture, and contact with humans and/or other animals
A total of 75 colonies were counted on the plate that received 1 mL of a diluted specimen. After calculating, it is determined that the total bacterial count in the original specimen was 75,000,000 colony forming units (CFUs) per mL. What was the dilution factor for the plated sample?
1:1,000,000
Animal viruses are typically what size?
20-1000 nm
What term is used to describe when a virus initially "sticks" to the host cell?
Adsorption
Which viral stage occurs first?
Adsorption
Which of the following are reliant on the viral capsid?
Adsorption and Penetration
A persistent infection could last how long in a host?
All of the these
Which of the following is a type of cytopathic effect?
All of these choices are correct.
Identify the different environments in which some viruses can replicate.
Animal cells, Bacterial cells, and Human cells
The viral capsid or viral proteins embedded in the envelope promotes the production of which of the following by the host?
Antibody
Typically, what is the immunological response against viral capsid and viral envelope antigens?
Antibody production
Which of the following describes the process of various viral "parts" coming together to produce complete virions?
Assembly
What functions do capsid proteins perform for naked viruses?
Attachment and Protection
What term is used to describe viruses which infect bacteria?
Bacteriophages
Viruses with negative-strand RNA molecules must first be converted to which of the following in the process of replication.
Be converted into a positive-strand of RNA
Adenovirus
Clumping of cells
Which of the following describes bacteriophages?
Complex, Polyhedral capsid head, and Flexible tail
A culture which contains one or more unwanted and often unidentified microbes.
Contaminated culture
Which of the following is not a major element of a microbial cell?
Copper
To cultivate (verb) or observable growth (noun)
Culture
Using a microscope, you observe some cells which have multiple nuclei because a virus has caused normal cells to fuse together. What is this observation called?
Cytopathic effect
Where are most RNA viruses replicated and assembled within the host?
Cytoplasm
The smallpox virus contains which of the following nucleic acid(s)?
DNA only
A single virion could contain a genome of which of the following?
DNA only and RNA only
The term virus was first used to describe the infectious agent of which of the following?
Disease of tobacco plants
Which type of microscope is usually used to examine viruses?
Electron
Which term is used to describe the process in which a virus is engulfed by a cell in a vacuole or vesicle?
Endocytosis
Identify all the methods that a virus can use to gain entry into an animal cell.
Engulfment/phagocytosis of the virus and Fusion of the viral envelope and the cell membrane
Many animal viruses will acquire which of the following from the host cell's membrane?
Envelope
Which term is used to describe the phospholipid bilayer found surrounding the capsid of some viruses?
Envelope
Select all of the statements that are true regarding penetration of animal viruses.
Enveloped viruses can penetrate by fusion., Enveloped viruses can penetrate by endocytosis., Nonenveloped viruses can penetrate by endocytosis., and Once inside the host, viruses become uncoated.
Louis Pasteur concluded that rabies was caused by a "living thing" larger than bacterial cells.
False
Once a standard curve has been prepared by plotting numbers of bacteria (CFU/mL) versus absorbance for one species of bacteria, this curve can be used for estimating bacterial numbers by measuring absorbance for any species of bacteria.
False
Spikes are glycoproteins of the viral capsid.
False
The International Committee on Taxonomy of Viruses has determined that there are only three orders of viruses.
False
The envelope is entirely formed from viral material.
False
The light microscope was critical in the discovery of viruses.
False
Treating the work area with disinfectant will kill all forms of microbes.
False
Viruses are ultramicroscopic because they range in size from 2 mm to 450 mm.
False
Viruses first appeared on Earth sometime after the rise of eukaryotic organisms.
False
Whether an organism is an autotroph or heterotroph depends on its source of nitrogen.
False
Which are advantages of the quadrant streak plate method when compared to the pour plate method?
It requires fewer materials. and It is a very quick process.
What advantage does the pour plate method have over the quadrant streak plate method?
It requires less skill.
You measure the absorbance of a bacterial culture two hours after inoculating a sterile medium, and then you continue to measure the absorbance every two hours for a total of three days. If you plotted the absorbance over time, what would the graph look like?
It would increase and then level off.
Some animal viruses can insert their genomes into a host cell's DNA. This process is called which of the following?
Latency
The discovery of the light microscope had what type of impact on the observation of viruses?
Little to none
Which term refers to a nutrient that is required by a microorganism in large quantities for use in cell structure and/or metabolism?
Macronutrient
Which of the following activities are not characteristics of viruses?
Maintain homeostasis, React to environmental factors, Replicate independently, and Metabolize food
If a virus were to infect a host cell but the cell's enzymes had been denatured, could the virus still replicate?
No, because the virus relies on host enzymes and machinery.
Which of the following describes viruses?
Non-living, infectious agent
Viruses belong to which of the following Kingdoms?
None of the choices are correct.
Where are most DNA viruses replicated and assembled within the host?
Nucleus
Which of the following characteristics are correct for viruses?
Obligate intracellular parasites, Acellular, and Infects very specific cell types
What term is used to describe viruses that can cause cancers?
Oncogenic
Which term refers to the diffusion of water through a semipermeable membrane? Multiple Cho
Osmosis
A cell harboring a virus that is not causing cytopathic effects is characteristic of which type of infection?
Persistent infection
Which of the following terms describes viruses in the carrier state within the host cells?
Persistent infections
Which of the following is a preformed viral protein that synthesizes DNA and RNA?
Polymerase
Which of the following is a group of complex viruses that lack a typical capsid and are covered by a dense layer of lipoproteins and fibrils?
Poxviruses
What is the primary function of the viral capsid and envelope?
Protection
Viruses are composed of which of the following?
Protein capsid and DNA or RNA
Capsomers are composed of which macromolecule?
Proteins
In which stage of viral multiplication would you expect to see "budding" occur?
Release
Which preformed enzyme is involved in the synthesis of DNA from RNA in retroviruses, such as HIV?
Reverse transcriptase
Bullet-shaped enveloped viruses are known as which of the following?
Rhabdoviruses
Which of the following describes the size of most viruses?
Smaller than 0.2 micrometers
Which of the following viral structures must be specific for adsorption?
Spike proteins
What term is used to describe the viral proteins which protrude from the envelope and aid in attachment to host receptors?
Spikes
Which best describes the shape of a helical virus?
Spiral
Viruses are classified into families based on genetic makeup and which of the following?
Structure
Which are the criteria used in classifying viruses into families?
Structure, Genetic makeup, and Chemical composition
A second-level culture where an isolated colony from one culture is taken and transferred into a new medium.
Subculture
If you transfer bacterial growth from a broth to an agar plate but nothing grows after incubation, what may have occurred?
The loop may have been too hot when making the transfer.
Microorganisms require small quantities of this nutrient for enzyme function and maintenance of protein structure.
Trace element
Which term describes the integration of an oncogenic virus into mammalian DNA, changing the characteristics of the host cell?
Transformation
Which term describes the tissue specificities of animal viruses for certain body cells?
Tropisms
A saprobe with a cell wall will utilize extracellular digestion.
True
Chemoautotrophs use inorganic nutrients for carbon and energy sources.
True
Facilitated diffusion and active transport require a carrier protein to mediate the movement across the plasma membrane.
True
Icosahedral viruses have the variation of containing an outside capsule.
True
Inorganic nitrogen must be converted to ammonium to be used by a cell.
True
The dilution factor of a particular bacterial culture made when 30 microliters (μL) is added to 270 μL of sterile broth is the same dilution factor as when 10 milliliters (mL) is added to 90 mL of sterile broth.
True
The growth curve of a particular bacterial strain should be the same for every growth experiment performed with that strain if the growth medium and conditions remain the same.
True
The hepadnavirus family is so named because viruses within the family infect the liver and possess DNA as their genetic material.
True
The image seen here does not represent a pure culture.
True
The poliovirus was successfully cultivated in a lab within the United States.
True
The viral-host relationship is extremely important for pathogenicity, mode of transmission, the immune response, and the human measures used to control viral infections.
True
Which is false regarding the viral envelope and the membrane of its host?
Viral glycoproteins are present in the host membrane but not in the viral envelope.
What does "obligate" mean in regard to viruses?
Viruses must have a host cell.
Which of the following increases as the number of bacteria in a sample increase?
absorbance
Bacteriophage go through similar stages as animal viruses except
adsorption.
Indicate the sites where microorganisms are likely to be found. (Select all that apply)
air, laboratory bench surface, hands, and computer keyboard
Which of the following characteristics are associated with transformed cells?
altered chromosomes, changes in cell surface molecules, and integration of viral DNA into host chromosome
Please select all of the following that represent viral characteristics.
are obligate intracellular parasites, have a 20 to 450 nanometer diameter, and are composed of a capsid surrounding a nucleic acid core
The goal of ______________ technique is to minimize the contamination of both original and newly inoculated cultures as well as to protect the laboratory worker from contamination.
aseptic
The laboratory work surface should be wiped with disinfectant (Select all that apply)
before beginning laboratory procedures., after completing the lab activities., and after a spill of microorganisms.
Which of the following is a possible mistake when performing a quadrant streak that could lead to no growth beyond the first quadrant? Select all that apply.
beginning the second quadrant streak while the loop is still hot
Classification of viruses into families involves determining all the following characteristics except
biochemical reactions.
Which of the following are the most useful using modern systems to classify a newly discovered virus?
capsid is icosahedral, genome is RNA, and envelope contains particular spike proteins
Please select criteria that are used to classify viruses.
capsid structure, presence/absence of an envelope, and genetic makeup
The capsid of a viral particle is composed of identical proteins called __________.
capsomer
Nutrient absorption is mediated by the
cell membrane.
Virus-induced damage to host cells, called __________ effects, can include changes in cell size and shape.
cytopathic
The movement of molecules from an area of high concentration to an area of lower concentration is called
diffusion.
The process of penetration occurs when viruses are taken into the cell followed by engulfment in a vesicle called a(n)
endosome
Which of the following parts of a virus is/are not always present?
envelope
The three basic groups of viruses based on morphology include
enveloped viruses, non enveloped viruses, and complex viruses.
The term obligate refers to
existing in a very narrow niche.
The movement of substances from higher to lower concentration across a semipermeable membrane that must have a specific protein carrier but no energy expenditure is called
facilitated diffusion.
An organism that can exist in both oxygen and oxygen-free environments is a/an
facultative anaerobe.
Cultures of a bacterial species were incubated out on the incubator shelf, in an anaerobic jar, and in a candle jar. After incubation there was moderate growth of cultures in the candle and anaerobic jars, but heavy growth of the culture on the incubator shelf. This species is a/an
facultative anaerobe.
The total nucleic acid content of a virus can be referred to as the viral
genome
The term phototroph refers to an organism that
gets energy from sunlight.
The inability of the HPAI H5N2 flu to move successfully from birds to humans is primarily attributable to
hemagglutinin proteins.
How is an inoculating loop or needle sterilized prior to use?
holding in the hottest part of the Bunsen burner flame until red-hot
Poliovirus and adenovirus have a capsid arranged in a symmetrical polygon structure called a(n)
icosahedron or icosahedral
Cytopathic changes in virally infected animal cells include
inclusions in the cytoplasm., clumping of cells., cell lysis., cytoplasmic inclusions., and formation of multinucleate syncytia.
The ________ is an appropriate tool to use for inoculating microorganisms into the butt of an agar slant.
inoculating needle
Which of the following terms is associated with the release of nonenveloped or complex viruses from the host cell?
lysis
Which of the following represents a virus family name?
Herpesviridae
Which of the following viruses has the longest multiplication cycle?
Herpesviruses
Which of the following is a term used to describe the different host cells which a virus can infect?
Host range
The length of a viral multiplication cycle is usually measured in which of the following units?
Hours
How is air contamination prevented when an inoculating loop is used to introduce or remove organisms from an agar plate?
How is air contamination prevented when an inoculating loop is used to introduce or remove organisms from an agar plate?
Different viruses can infect which of the following?
Human, bacterial, or plant cells
What term is used to describe the capsid of a virus which has 20 equally spaced panels of capsomers forming a symmetrical structure?
Icosahedral
The material which provides the nutrients for growth
Medium
Which metric unit best describes viruses?
Micrometers
Which is not a host component from which viruses bud?
Mitochondrion
A culture which contains two or more species which can be easily differentiated.
Mixed culture
Which of the following is correct about viruses?
Most viruses cannot be seen with a light microscope.
Please select all of the statements which are true regarding isolated colonies.
The colony results from a single cell or a cluster of cells multiplying into a visible mass., The cells within the colony are all the same species., and Isolated colonies form on solid nutrient media.
The viral envelope is compositionally different from a non-infected host cell because of the presence of which of the following?
Viral proteins
Which are used for placement of a virus into a particular family?
Viral size, Nucleic acid strand number, Presence of envelope, and Type of capsid
Which is most important for attachment of a virus to a host cell?
Viral specificity for host receptors
Which of the following is a fully formed virus that is able to establish an infection in a host cell?
Virion
Which of the following generally carries the least amount of genetic material?
Virus
Which of the following is the smallest in relative size?
Virus
Which type of microbe is considered the most abundant on earth?
Viruses
The cause of viral infections remained unknown for many years longer than other types of infections due to which of the following reasons?
Viruses are not visualized by light microscopes. and The techniques used to observe other pathogens were useless with viruses.
Which of the following best explains why viruses have so few genes?
Viruses do not have metabolic pathways.
