Microbiology, Chapter 12, Flash Cards
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.
