MCB 11 Chapter 6D - Survey of Microorganisms: Viruses, Viroids, and Prions

These flashcards cover the essential vocabulary and concepts related to microorganisms, specifically focusing on viruses, viroids, and prions, as discussed in the lecture.

Viruses

Non-living obligate intracellular parasites that replicate only in living cells. Nucleic acid encased in a protein shell which may be surrounded by a lipid-containing membrane.

Capsomeres

Protein/capsid subunits arranged in a precise and highly repetitive manner around the nucleic acid.

Viral Symmetry

Can be helical (rod shaped), icosahedral (spherical w/ 20 triangular faces & 12 vertices), or complex (asymmetrical)

Infectious Agents

Viruses, Viroids, Prions

Non-living obligate intracellular parasites

Virus Nucleic Acid

Can be either DNA or RNA, linear or circular, double or single-stranded, segmented or non-segmented

Virus Proteins

Serve as protection against inactivation by nucleases; participate in attachment to host; facilitate transfer of viral NA from 1 host cell to another; initiation of virus replication; provide structural symmetry; determine antigenic property

Virus Lipids

Found in virus envelopes; derived from host cell

Virus Carbohydrates

Present as glycoproteins in virus envelopes; virus-coded; attach virus to host cell via receptors; also function as antigens

Embryonated Eggs Cultivation

Virus cultivation wherein viral growth is indicated by death of embryo, embryo cell damage, or formation of lesions

Living Animals Cultivation

Viral cultivation where either an animal is observed for signs of disease or is killed so infected tissues can be examined for the virus.

Cell Cultures Cultivation

Viral cultivation wherein a tissue is treated with enzymes to separate the cells; the cells are then suspended in culture medium; normal cells or primary cells grow in a monolayer across the container. The transformed cells / continuous cell cultures do not grow in a monolayer.

Viroids

Infectious agents consisting of a single piece of RNA without a protective coat.

Prions

Infectious proteins that cause neurodegenerative diseases, consisting of protein only.

Nucleocapsid

Structure formed by nucleic acid and a protein coat in viruses.

Virion

Complete infective form of a virus outside a host cell.

Capsid

Protein shell that encases the viral genome.

Genome

The complete set of genetic material in a virus.

Helical viruses

Viruses with rod-shaped symmetry.

Icosahedral viruses

Viruses with spherical shape, featuring 20 triangular faces.

Complex viruses

Viruses with asymmetric structures, including bacteriophages.

Naked virus

Virus without an envelope, consisting only of nucleic acid and a capsid.

Enveloped virus

Virus with an outer lipid membrane derived from the host cell.

Viral replication cycle

The process by which a virus infects a host and produces new virions.

Attachment (adsorption)

The first step in the viral replication cycle, where the virus adheres to the host cell.

Penetration

The step where viral nucleic acid enters the host cell.

Synthesis of viral components

The process of replicating viral nucleic acid and proteins inside the host.

Assembly

The stage of the viral replication cycle where new virions are constructed.

Release

The final step of the viral replication cycle, where new virions exit the host cell.

Lytic cycle

Virus cycle resulting in the destruction of the host cell.

Lysogenic cycle

Virus cycle where it integrates its DNA into the host without immediate destruction.

Bacteriophage

A virus that infects bacteria.

SARS-CoV-2

A novel coronavirus responsible for the COVID-19 pandemic.

HIV

Human Immunodeficiency Virus, which can lead to AIDS.

Dengue virus

An RNA virus transmitted by mosquitoes causing Dengue fever.

Hepatitis B

A vaccine-preventable liver infection caused by the hepatitis B virus.

Rabies virus

Virus spread through animal bites, affecting the brain and is often fatal.

Cytopathic effects

Detection of virus infected cells: change in host cells due to viral infection, often observable under a microscope. E.g. after human cervical cell is infected w/ HHV-2, the nuclei is filled with viruses.

Hemagglutination test

A laboratory test for detection of virus infected cells through the clumping of red blood cells.

Plaque assay

A method for detection of virus infected cells based on the formation of clear areas in a lawn of host cells/culture.

Basis of virus classification

• Genome

• Structure

• Route of transmission

  • enteric

  • respirstory

  • zoonotic

  • sexually-transmitted

• immunologic properties

• pathology / symptomatology

Virus replication cycle

1. Attachment (adsorption of phage virion)

2. Penetration of viral nucleic acid

3. Synthesis of viral nucleic acid & protein

4. Assembly & packaging of new viruses

Entry of Animal Viruses

Three mechanisms

• Direct penetration

• Membrane fusion

• Endocytosis

Baltimore classification

Classification of viruses based on their genome type and method of replication.

RNA viruses

Viruses that use RNA as their genetic material.

Replication of DNA viruses

1. attachment

2. penetration

3. NA synthesis

4. protein synthesis

5. assembly

6. release

Replication of RNA viruses

1. attachment

2. penetration

3. protein synthesis

4. NA synthesis

5. protein synthesis

6. assembly

7. release

Replication of a Retrovirus

The virion carries two identical copies of the RNA genome (orange). Reverse transcriptase, carried in the virion, makes single-stranded DNA from viral RNA and then double-stranded DNA that integrates into the host genome as a provirus. Transcription and translation of proviral genes leads to the production of new virions that are then released by budding.

Bacteriophages

Viruses that infect bacteria; can be lytic/virulent, or temperate/lysogenic

DNA viruses

Viruses that use DNA as their genetic material.

Carbohydrates in viruses

Molecules found in viral envelopes, often serving as receptors and antigens.

Lipids in viruses

Components found in the viral envelope, derived from host cell membranes.

Glycoproteins

Molecules in viral envelopes that facilitate attachment to host cells.

Cell culture

Method for growing viruses in a controlled environment using live cells.

Vaccination

Administration of a vaccine to induce immunity against viral diseases.

Antigenic properties

Characteristics of a virus that determine the immune response it elicits.

Viral enzymes

Proteins encoded by viruses that facilitate viral replication and assembly.

Antibody

A protein produced by the immune system that binds to specific antigens.

Immune response

The body's defense mechanism against viral infections.

Obligate intracellular parasites

Organisms that can only reproduce inside a host cell.

Non-segmented viruses

Viruses whose genome consists of a single continuous piece of nucleic acid.

Segmented viruses

Viruses whose genome is divided into separate pieces.

RNA polymerase

Enzyme that synthesizes RNA from a DNA template in viruses.

Reverse transcriptase

An enzyme used by retroviruses to convert RNA into DNA.

Viral pathogenesis

The process through which a virus causes disease.

Viral transmission

The method by which a virus spreads from one host to another.

Zoonotic infections

Diseases transmitted from animals to humans.

Vaccination strategies

Approaches used to prevent viral infections through immunization.

COVID-19 symptoms

Common signs of infection include fever, cough, and fatigue.

Viroids

Consists of a single piece of nucleic acid (RNA) without a protective coat; only abt 30 known; cause serious plant diseases

Prions

Contain only protein, no nucleic acid; smallest infectious agent

Viroid diseases

Plant diseases caused by viroids, characterized by stunted growth and deformity.

Prion diseases

Neurological disorders caused by infectious prions, such as Mad Cow Disease.

Viral shedding

The release of virus particles from an infected host.

Serological tests

Laboratory tests that detect antibodies or antigens in a sample.

Genome sequencing

Determining the complete DNA or RNA sequence of a virus.

Viral evolution

The process by which viruses change and adapt over time.

Interferon

Proteins produced by host cells in response to viral infections.

Public health measures

Strategies implemented to prevent and control viral outbreaks.

Diagnostic methods

Techniques used to identify viral infections in patients.

Lytic or Virulent bacteriophage

Bacteriophage released by cell lysis

Temperate or Lysogenic bacteriophages

Bacteriophage where no lysis occurs but lytic cycle may be spontaneously expressed