Microbiology Test 3 Review

How is a virus with a +RNA different from one with a -RNA? What does that mean?

+RNA acts as mRNA for protein synthesis; -RNA has an enzyme which can convert the RNA into mRNA (-RNA is a template for transcription of multiple +ssRNA genomes)

How are viruses normally cultured and grown (for example to make vaccines)?

Phages are grown inside suitable host cells (embryonic chicken eggs or bacterial cells) In bacterial cells they can be maintained in either liquid cultures or agar plates.

Which type of antibody is in saliva?

IgA

Which type of antibody binds to mast cells and basophils?

IgE

Which type of antibody can bind 10 antigens?

IgM

Name the five classes of antibodies and where they are found:

IgM: early stage of infection- primary response IgG: in circulation major type and can cross placenta- long term protection IgA: in tears, saliva, mucus of respiratory tract, breast milk IgD: possibly on plasma membrane of B-cell to recognize specific AG. function not yet clarified IgE: attached to mast cells and basophils through it Fc portion

Viruses can change spikes to avoid the immune system. Which virus is best noted for those changes?

Influenza

Which disease is caused by a virus in the family, Orothomyxoviridae:

Influenza virus

What is the basic difference between acquired and innate immunity?

Innate: (nonspecific) resistance against many types of microorganisms. Acquired (adaptive) resistance against a specific type of microorganism.

Name 4 naked viruses:

Rhinovirus, Enterovirus, Hepatitis A, Noro virus, Reovirus, Adenovirus, Papilloma virus, Parvovirus B19

Name three viruses in the family Picornaviridae:

Rhinovirus, Hepatitis A, and Enterovirus

Name two disease causing viruses that belong to the family of Paramyxoviridae:

Mumps and Measles

Name a bacterium that can exist inside a phagocytes:

Mycobacteria

Name two viruses that cause cancer:

Papilloma and Epstein Barr virus

How would you describe the following transmission of disease?

a fly carries worm larvae on its legs from feces to food: the anopheles mosquito transmits malaria to a young child: biological vector a classmate with a rhinovirus coughs and you inhale the microorganism: droplet transmission giardiasis from drinking contaminated water: waterborne transmission mononucleosis from kissing a partner with mono: direct contact transmission pinkeye from wiping your hands on a towel and then touching your eyes: direct contact transmission an STD from sexual intercourse: direct contact

Define antigen:

a specific chemical (often surface protein) that causes an immune response.

How does the animal virus often obtain it's envelope?

acquires it from host cell during viral replication or release.

What is meant by immunoglobulins?

antibodies

What is the difference between and endo- and exotoxin?

endotoxins are secreted inside the host cell. exotoxins are secreted outside the host cell and affect the body.

Are all capsomeres of different viruses arranged in the same geometric pattern?

no- because rabies has a helical shape; polio has a polyhedral. They differ depending on the virus.

Do viruses undergo mitosis?

no- they are dependent upon host enzymes to produce new virions.

Are there viruses that contain both RNA and DNA?

no- they only contain one or the other.

Can viruses be seen with a light microscope?

no- viruses can only be seen with an electron microscope.

What word is used to describe these viruses:

oncogenic

What is specialized transduction?

only certain host sequences are transferred along with phage DNA. (usually lysogenic stage first)

What is an endotoxin?

part of the cell wall of gram negative bacteria (lipid A)

What is an envelope of a virus made of?

phospholipids

Name some shapes seen for capsids:

polyhedral, helical and complex

What is a "spike" and where is it located?

projections of the envelope or capsid- glycoproteins for attachment. Can elicit an immune response

Name 4 common portals of entry for infection:

skin, wounds, placenta, any body opening, mucus membranes (digestive, urinary, respiratory, reproductive tracts)

What word is used to describe these viruses:

teratogenic

Antibiotic testing shows that the Staphylococcus aureus is MRSA. What does that mean?

that it is Methicillin resistant Staphylococcus aureus.

How does the bacterial capsule play a role in phagocytosis?

the bacterial capsule protects against phagocytosis

What makes a virus host specific?

the chemical attraction and exact fit between proteins and glycoproteins on the virion and complementary protein and glycoprotein receptors on the cell membrane.

What is generalized transduction?

the transducing phage carries a random DNA segment from the donor host cell's chromosome or plasmids to a recipient host cell. (usually lytic stage)

Concerning animal viruses there are two cycles: productive and latent. Explain both:

Virus latency is the ability of a pathogenic virus to lie dormant within a cell, denoted as the lysogenic part of the viral life cycle. In the productive cycle, a virus can reactivate and begin producing large amounts of viruses known as the lytic part of the viral life cycle, and stays within the host indefinitely.

Name the five general stages of the replication cycle in viruses:

1.attachment: attachment of the virion to the host; 2.entry: the entry of the virion or it's genome into the host; 3.synthesis: synthesis of new nucleic acids and viral proteins by the host cells enzymes and ribosomes; 4. assembly: assembly of the new virions inside the host cell; 5. release: release of the new virions from the host.

What is a bacteriophage? Why is it significant?

A bacteriophage is a virus that infects and usually destroys bacterial cells. It is significant because it can potentially be used as an alternative to antibiotics. They are excellent tools for the general study of viruses because they are easier and less expensive than animal or human viruses to culture.

What's the difference between a capsomere and a capsid?

A capsid is a protein coat and determines the virus' shape. The capsid is typically made up of many identical protein units. Each individual protein unit is called a capsomere.

What's the difference between a naked virus, nucleocapsid and prion?

A naked virus is a virion without a membrane (envelope). A nucleocapsid is a nucleic acid and it's capsid. A prion is a proteinaceous infectious particle that lacks nucleic acids and replicates by converting similar normal protein into a new prion.

What's the difference between virion and viroid?

A virion is a virus outside of a cell consisting of a proteinaceous capsid surrounding a nucleic acid core. A viroid is an extremely small circular piece of RNA that is infectious and pathogenic in plants.

What does it mean when we say a virus has a specific CPE? Give two examples:

CPE- means cytopathic effect. Rabies virus: Negri bodies (clumps of virus) within the cells. RSV Virus: syncytia (cells in the lung merge to form large multinucleated cells)

Name a human disease believed to be caused by a prion:

Creutzfeldt-Jakob disease

Name the virus that causes Burkitt's Lymphoma:

Epstein Barr Virus

Which virus affects Thelper cells?

HIV

Name a virus that contains reverse transcriptase:

HIV virus

Name three disease causing viruses that belong to the Herpesviridae:

Herpes Simplex virus, Cytomegalyvirus, Epstein Barr virus, Varicellovirus

Name two viruses that cause latent infections:

Herpes Simplex, Varicella, Papilloma

Which of the following viruses are RNA viruses?

Herpes virus: no- DNA Hepatitis B virus: no- DNA Hepatitis A virus: yes Rhinovirus: yes Influenzavirus: yes Papilloma virus: no- DNA Polio virus: yes

Name three viruses that cause congenital defects:

Herpes, Rubella, Cytomegalyvirus

What is the function of lysozyme and where is it made?

Lysozyme is an enzyme used to break down bacterial cell walls. It is found in tears and saliva.

Concerning bacteriophages- there are two cycles: lytic and lysogenic. Explain both:

Lytic: bacterial cell is destroyed through release of virus. Stages of Lysis: attachement, entry, metabolism, assembly, release. Lysogeny: bacterial cell is not destroyed. Stages of Lysogeny: attachment, entry, virus remains inactive as prophage in cell's chromosome

Name a virulence factor that breaks down complement:

M protein

Name three diseases that have animal reservoirs:

Malaria, Plague, Lyme disease

What is the mucociliary escalator? Where is it and why is it important?

The mucociliary escalator covers most of the bronchi, bronchioles and nose. It is composed of two basic parts; the mucus-producing goblet cells and the ciliated epithelium. The cilia are continually beating, pushing mucus up and out into the throat. The mucociliary escalator is a major barrier against infection. Microorganisms hoping to infect the respiratory tract are caught in the sticky mucus and moved up by the mucociliary escalator. Smoking paralyzes the cilia therefore making smokers more susceptible to URI.

How do these stages differ in bacteriophages vs animal viruses?

bacteriophage- lysogenic=prophage; animal virus-latent=provirus.Also, when the bacteriophage enters a bacterium, only the DNA/RNA is released into the cell (capsid remains outside). However, when viruses enter animal cells, the capsid goes into the cell creating the extra step of uncoating.

Why is it interesting to know if a virus is "naked"?

because naked viruses are usually very resistant.

What do antibodies do?

bind with the antigen causing phagocytosis, agglutination, activate complement, neutralize toxins

How is a virus similar to chlamydia? How is it different?

both are OIP's. Chlamydia is a bacterium, but in some ways it's one that acts more like a virus. It is virus-like, because it is dependent on molecules from its host organism to reproduce. In contrast to viruses, they have both DNA and RNA, cytoplasmic membranes, functioning ribosomes, reproduction by binary fission, and metabolic pathways.

What is meant by a cytopathic effect? Name two examples:

can be used by virologists to determine type of viral infections. Some viruses cause cells to swell, others to fuse, etc. (may be unique for a virus) Examples include: Rabies virus (Negri bodies- clumps of virus within the cells), and RSV virus (syncytia - cells in the lung merge to form large multinucleated cells)

Why is that an important enzyme?

can synthesize DNA from the virus RNA- kind of like lysogeny but now with human cells

Name two virulence factors that protect against phagocytosis:

capsules, mechanisms that help the bacteria survive inside phagocytes

There are also coagulase-positive staph and coagulase-negative staph. Which would you expect to be more pathogenic? What does coagulase do?

coagulase positive staph is considered to be more pathogenic; however coagulase negative staph can be pathogenic in immunocompromised patients. Coagulase causes blood to clot.

What is an antibody titer?

concentration of a substance (antibodies) / volume

Most enveloped viruses gain entrance into a host cell by____________ of the viral envelope with the ______________.

endocytosis; membrane

Define antibody:

made in response to an antigen (made by an activated B-lymphocyte) antibody attaches to antigen so that it can be phagocytized.

Which cells make it?

viral infected body cells

A complete virus particle is called a(an):

virion

What is meant by the virulence factor?

virulence factors are factors that help a microorganism cause disease.