Microbiology Factors Affecting Viral Survival

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Questions and Answers

What is the temperature range that can generally inactivate heat?

56-60°C for 30 minutes (correct)

60-70°C for 30 minutes

70-80°C for 1 hour

50-55°C for 1 hour

What is the pH range that can destroy most viruses?

pH below 5 and alkaline pH above 9 (correct)

pH below 3 and alkaline pH above 11

pH below 6 and alkaline pH above 8

pH below 4 and alkaline pH above 10

What is unique about the glycerol's effect on viruses and bacteria?

Both viruses and bacteria survive 50% glycerol

Viruses are destroyed by 50% glycerol, while bacteria survive

Both viruses and bacteria are destroyed by 50% glycerol

Bacteria are destroyed by 50% glycerol, while viruses survive (correct)

What type of agents are most effective against viruses?

Oxidizing agents Signup and view all the answers

What is the main characteristic that distinguishes viruses from bacteria in terms of reproduction?

Complex reproductive processes Signup and view all the answers

What is the composition of a virion?

DNA or RNA and a protein shell Signup and view all the answers

How are viruses classified based on their host specificity?

Bacteria, animal, and plant viruses Signup and view all the answers

What is the definition of virology?

The branch of microbiology concerned with viruses and viral diseases Signup and view all the answers

What is the term for the entire infectious unit of a virus?

Virion Signup and view all the answers

What is essential for a virus to replicate?

A host cell Signup and view all the answers

What is the function of the capsid?

To encase and stabilize the viral nucleic acid Signup and view all the answers

What is the effect of viral antiserum on the virion?

It neutralizes the virion Signup and view all the answers

What is a characteristic of viruses?

They can infect a wide range of organisms, from unicellular to multicellular Signup and view all the answers

What is the result of treating viral nucleic acid with ribo- or deoxyribonuclease?

It is hydrolyzed Signup and view all the answers

What is a by-product of the viral replicative cycle?

Empty capsids Signup and view all the answers

What is missing from all viruses?

An ATP-generating system Signup and view all the answers

What is the primary reason why large viruses of the pox group can be seen using ordinary light microscopes?

Due to the use of staining procedures Signup and view all the answers

What is the purpose of mixing a virus suspension with a suspension of polystyrene latex particles of known concentration in electron microscopy?

To count the number of virus particles in the suspension Signup and view all the answers

What is responsible for the increased limit of resolution in electron microscopes compared to light microscopes?

The shorter wavelength of high-velocity electrons Signup and view all the answers

What is the primary application of the fluorescent antibody technique in virology?

To demonstrate viral antigens in tissues Signup and view all the answers

What is the function of structured proteins in viruses?

To have several important functions Signup and view all the answers

What is the minimum diameter of virus particles that can be resolved by electron microscopes?

Less than 1 nm Signup and view all the answers

What is the advantage of using electron microscopes over light microscopes in virology?

Electron microscopes have a higher limit of resolution Signup and view all the answers

What can be recognized using the fluorescent antibody technique and electron microscopy in infected animals or humans?

Characteristic histological and cytological changes Signup and view all the answers

What is the primary function of the structural proteins of a virus?

To protect the viral genome against inactivation by nucleases Signup and view all the answers

How can the structural proteins of a virus be studied?

By dissociating the proteins of the virus particle with a detergent and then separating them by electrophoresis through polyacrylamide gel matrix Signup and view all the answers

What type of nucleic acid do most major families of RNA-containing animal viruses have?

Single-stranded RNA Signup and view all the answers

Which of the following viruses is an exception to the rule that DNA-containing animal viruses have double-stranded DNA genomes?

Parvovirus Signup and view all the answers

What is the function of the enzyme reverse transcriptase in RNA tumor viruses?

To make a DNA copy of virus RNA Signup and view all the answers

What is the purpose of the protein hemagglutinin in influenza virus?

To attach to susceptible cells Signup and view all the answers

How can the type of nucleic acid and strandedness be determined?

By staining with acridine orange and identifying the nucleic acid by color reaction and enzyme digestion tests Signup and view all the answers

What is a characteristic of the structural proteins of many viruses?

They are very specialized molecules designed to perform a specific task Signup and view all the answers

Which virus causes cytomegalic inclusion disease?

Cytomegalovirus Signup and view all the answers

What is the characteristic of Poxviridae family?

Contain double-stranded DNA genome Signup and view all the answers

Which virus is associated with several human malignancies?

EB virus Signup and view all the answers

What is the characteristic of Picornaviridae family?

Contain single-stranded RNA genome Signup and view all the answers

Which virus is the most common cause of colds in humans?

Rhinovirus Signup and view all the answers

What is the characteristic of Reoviridae family?

Contain double-stranded RNA genome Signup and view all the answers

Which virus is an agent of infantile gastroenteritis?

Rotavirus Signup and view all the answers

What is the characteristic of Varicella-zoster virus?

Causes zoster and chickenpox Signup and view all the answers

Study Notes

Characteristics of Viruses

Viruses are inactivated by temperatures of 56-60°C for 30 minutes
pH affects viral survival, with most viruses destroyed at pH below 5 and above 9
Glycerol affects viruses and bacteria differently, with 50% glycerol surviving most viruses but destroying bacteria
Bactericidal agents, such as Phenol, are not efficient as viral disinfectants, whereas oxidizing agents are most effective against viruses
Antibiotics and chemotherapeutic agents, like Sulfonamides, penicillin, streptomycin, and tetracyclines, have little effect on viruses

Reproductive Processes

Viral reproductive processes differ from bacterial binary fission
Viruses contain only one kind of nucleic acid, which is covered by a protein coat

Definition of Virology

Virology is the branch of microbiology that deals with viruses and viral diseases

Nature of Viruses

Viruses are minute infectious agents that are not resolved in the light microscope
They lack independent metabolism and replicate only within living host cells
They have genetic continuity and the possibility of mutation
They are morphologically heterogeneous, occurring as rod-shaped, spherical, or polyhedral forms
Viruses are composed of a nucleic acid (the nucleoid), DNA or RNA (but not both), and a protein shell or capsid
The protein shell contains and protects the nucleic acid
Viruses are classified according to host specificity, origin, mode of transmission, or the manifestation they produce

Viral Structure

The individual particle or virion consists of nucleic acid and a protein shell or capsid
Capsid: a symmetric protein shell that encloses the nucleic acid genome
Nucleocapsid: the capsid together with enclosed nucleic acid
A virion lacks certain components essential for its replication and must depend on the host cell for these missing factors
One component missing from all viruses is an ATP-generating system

Microscopy

Although most viruses cannot be seen by ordinary microscopic methods, the light microscope has some important applications in virology
Large viruses of the pox group can be demonstrated by staining procedures
The fluorescent antibody technique is valuable for demonstrating viral antigens in tissues
Electron microscopy has brought even the smallest viruses into visible range and is capable of resolving particles with diameters of less than 1 nm

Chemical Composition of Viruses

Viral Protein: serves to protect the viral genome, participate in attachment to susceptible cells, and determines the antigenic characteristics of the virus
Virus structural proteins may be very specialized molecules designed to perform specific tasks
Viral Nucleic Acid: contains a single kind of nucleic acid, either DNA or RNA, that encodes the genetic information necessary for the replication of the virus
Viral Lipids: some viruses contain lipids as part of their structure

Virus Families

Poxviridae Family: relatively large, brick-shaped or ovoid viruses containing a double-stranded DNA genome and protein, enveloped by double membranes
Picornaviridae Family: small, ether-resistant viruses that contain single-stranded RNA
Reoviridae Family: ether-resistant viruses that contain double-stranded RNA

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Description

This quiz assesses your understanding of the factors that affect the survival of viruses, including heat, pH, glycerol, and various disinfectants. Test your knowledge of microbiology and virology concepts.