Microbiology, Chapter 12, Flash Cards

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Syncytium

A large multinucleated cell formed by the fusion of many uninuclear cells.

Temperate phage

A phage capable of lysogeny.

Rise period

During viral culture, the time when cells lyse and viral progeny enter the medium.

Envelope

For a virus, a membrane enclosing the capsid, or core particle.

Tegument

The contents of a virion between the capsid and the envelope.

Batch culture

The growth of bacteria in a closed system without additional input of nutrients; oxygen may be provided.

Tissue tropism

The range of host tissue that a pathogen can infect.

Uncoating

The release of a viral genome from its capsid, following entry of the virion into a host cell.

Transformation

1. The internalization of free DNA from the environment into bacterial cells.2. The viral conversion of a normal cell to a cancer cell.

Chapter 12: Viruses

12.1 What Is a Virus? 12.2 Viral Genomes and Diversity 12.3 Virus Replication and Culture 12.4 Papillomavirus: DNA Genome 12.5 Influenza Virus: RNA Genome 12.6 Human Immunodeficiency Virus: Reverse Transcription

Virulent phage

A bacteriophage that reproduces entirely by a lytic cycle.

Plaque

A cell-free zone on a lawn of bacterial cells caused by viral lysis.

Baltimore model

A classification scheme that organizes viruses by genome type and method of replication; was devised by David Baltimore.

Oncogene

A gene that, through mutation or inappropriate expression, can lead to cancer.

Surface receptor

A host cell membrane protein that is recognized and bound by a microbe having a complementary binding molecule on its surface.

Antigenic shift

A major change in a viral antigen that occurs when two (or more) strains of a virus with segmented genomes infect the same host cell and re-sort their genome segments. The resulting chimeric virus can express a new combination of surface antigens (such as influenza hemagglutinin and neuraminidase) that can alter virulence or enable the infection of new hosts.

Plaque-forming unit (PFU)

A measure of the concentration of phage particles in liquid culture.

Lentivirus

A member of a family of retroviruses with a long incubation period. An example is HIV.

Cell fusion

A method of viral spreading in which an infected host cell fuses with an uninfected cell, allowing the virus particles to enter the uninfected cell through their common cytoplasm.

Retroelement

A mobile genetic element in the genome of an organism.

Virus

A noncellular particle containing a genome that can replicate only inside a host cell.

Prophage

A phage genome that has integrated into a bacterial host genome.

Reading frame

A sequence of nucleotides in DNA or RNA whose nonoverlapping triplets are potentially translatable into a polypeptide.

Cloning vector

A small genome, often a plasmid, into which foreign DNA can be inserted for cloning.

Provirus

A viral genome that is integrated into the host cell genome.

Spike protein

A viral glycoprotein that connects the membrane to the capsid or the matrix and may be involved in viral binding to host cell receptors.

Lytic infection

A viral life cycle in which progeny virions are released from the host cell by virus-induced rupturing of the cell membrane.

Lysogeny

A viral life cycle in which the viral genome integrates into and replicates with the host genome but retains the ability to initiate host cell lysis.

Filamentous virus

A virus consisting of a helical capsid surrounding a single-stranded nucleic acid.

Virion

A virus particle.

Oncogenic virus

A virus that causes cancer.

Retrovirus

Also called RNA reverse-transcribing virus. A single-stranded RNA virus that uses reverse transcriptase to generate a double-stranded DNA copy of its genome.

Bacteriophage

Also called phage. A virus that infects bacteria.

RNA reverse-transcribing virus

Also called retrovirus. A single-stranded RNA virus that uses reverse transcriptase to generate a double-stranded DNA copy of its genome.

Reverse transcriptase

An enzyme that produces a double-stranded DNA molecule from a single-stranded RNA template.

RNA-dependent RNA polymerase

An enzyme that produces an RNA complementary to a template RNA strand.

Prion

An infectious agent that causes propagation of misfolded host proteins; consists of a defective version of the host protein.

Viroid

An infectious naked nucleic acid.

One-step growth curve

Graphical representation of a lytic virus life cycle -- from attachment through infection, formation of progeny, and cell lysis -- in a system with a fixed number of host cells.

Antigenic drift

Random mutations in a viral genome that cause minor changes in the structure of viral surface antigens, such as influenza hemagglutinin and neuraminidase. The consequence is a new viral strain that might better evade the host immune system.

Transmission

The movement of a pathogen from one host to another.

Burst size

The number of virus particles released from a lysed host cell.

Reassort

The process by which genome segments come together from different influenza strains infecting the same host cell.

Capsid

The protein shell that surrounds a virion's nucleic acid. Within an enveloped virus, such as HIV, the capsid may be called a core particle.

Lysis

The rupture of the cell by a break in the cell wall and membrane.

Host range

The species that can be infected by a given pathogen.

Eclipse period

The time after viral genome injection into a host cell but before complete virions are formed.

Transduction

The transfer of host genes between bacterial cells via a bacteriophage.


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