Microbiology - Chapter 13 Terms

latent infections

Viral genome remains silent within a host cell, yet can reactivate to direct a productive infection

productive infection

Viral infection in which more viral particles are produced

latent infection

Viral infection in which the viral genome is present but not active, so viral particles are not being produced

lytic infection

Viral infection of a host cell with a subsequent production of more virus particles and lysis of the cell

viroid

An infectious agent of plants that consists only of RNA

prion

An infectious agent that causes a neurodegenerative disease; consists of protein similar in amino acid sequence to a normal protein in the body

persistent infections

Can continue for years, or even the life of the host with or without symptoms

retroviruses

Carry reverse transcriptase within the virion

plaques

Circular zones of clearing

chronic infections

Continuous production of low levels of viral particles

antigenic shift

Major change in viral surface antigen that render antibodies made against the previous version ineffective

budding

A process whereby the virus acquires its envelope

replicase

A virally coded RNA polymerase used in the replication of RNA viruses

bacteriophage

A virus that infects bacteria; often shortened to phage

CRISPR system

Mechanism by which bacterial cells maintain a historical record of phage infections, and thereby become immune to subsequent infections by the same phages; the system also protects against other types of foreign DNA

plaque assay

Method used to measure the number of viral particles present in a sample

arboviruses

Named because they spread by arthropods such as mosquitos, ticks, and sandflies

generalized transduction

Results from a packaging error during phage assembly

specialized transduction

Results from an excision mistake made by a temperature phage during its transition from a lysogenic to a lytic cycle

provirus

Silent viral genome

inclusion body

Site of viral replication

antigenic drift

Slight changes in the viral surface antigen that render antibodies made against the previous version ineffective

plaque assays

A method used to determine the number of viral particles in a suspension

lysogen

A bacterium that carries phage DNA (the prophage) integrated into its genome

lysogenic conversion

A change in the phenotype of a lysogen as a consequence of the specific prophage it carries

lysogenic conversion

A change in the properties of a bacterium conferred by a prophage

virion

A complete virus in its inert non-replicating form; also referred to as a viral particle

lytic / virulent phages

Exit the host at the end of the infection cycle by lysing the cell

temperate phages

Have the option of either directing a lytic infection (productive infection) or incorporating their DNA into the host cell genome. The latter situation is called a lysogenic infection, and the infected cell is a lysogen

prophage

Integrated phage DNA in a bacterial host DNA

primary cultures

Obtaining animal cells for culture by removing tissue from an animal, then process it to get individual cells. These cells can then be grown in a Petri dish with a liquid nutrient medium

repressor

Prevents expression of the gene required for excision, essential for maintaining the lysogenic state

apoptosis

Programmed cell death

restriction-modification systems

Protect bacteria from phage infection by quickly degrading incoming foreign DNA. Do this through restriction enzymes and and modification enzymes

spikes

Stick out from either the lipid bilayer of enveloped viruses or the capsid of naked viruses

acute infections

Sudden onset of symptoms of a relatively short duration

reverse transcriptase

Synthesizes DNA from an RNA template

nucleocapsid

The capsid together with the nucleic acid it encloses

titer

The concentration of infections phage particles in the original phage suspension

burst size

The number of phage particles released when a cell lyses

phage induction

The process of destroying the repressor protein, thus causing the prophage to be excised from the chromosome

capsid

The protein coat of a virus. Composed of identical protein subunits called capsomers

cell culture / tissue culture

Used to cultivate most animal viruses. Animal cells are used as host cells for the virus culture

productive infections

Virus infection in which more virions are produced

naked viruses

Virus that do not have an envelope

enveloped viruses

Viruses with a lipid bilayer outside of the capsid