Ch 13 Viruses Nester Microbiology

lysogenic conversion

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

titer

concentration of infectious phage particles in the original phage suspension

tumor suppressor genes

genes that inhibit cell growth

proto-oncogens

genes that stimulate cell growth

plaque assay

method used to measure the number of viral particles present in a sample by counting the number of plaques.

provirus

silent viral genome

filamentous phage

single stranded DNA phage that look like long fibers, these phages cause productive infections but the process does not kill the host cell. infected cells grow more slowly than uninfected cells.

matrix protein

the _________ __________ is located between the nucleocapsid and the envelope

nucleocapsid

the capsid plus the nucleic acid is called the...

T4

the most studied lytic phage

lambda phage

the most thoroughly studied temperate phage

replication of dsDNA

uses the host RNA polymerase to transcribe DNA

replication of ssDNA

in order to replicate a compliment single stranded molecule must be made, it will either be + or -,

primary culture

individual cells processed from removed animal tissue in a nutrient medium

viroid

infections agnt that consists only of RNA molecules, no protein coat

generalized transducing particles

phage heads that contain only bacterial genes instead of phage genes

budding

process where the virus acquires an envelope as it leaves the cell, this may trigger apoptosis

capsomere

protein subunits that make up the capsid, they are all identical, this allows for less genetic information and simple assembly instructions, saves room on the genome

specialized transduction

results from an excision mistake made by a temperate phage during its transition from a lysogenic to a lytic cell. It takes a piece of the chromosome with it. Now each virus takes the DNA with it, no need for homologous recombination.

replication of dsRNA

the process in which mRNA is synthesized off the virus genetic material, there must be a RNA dependent RNA polymerase or replicase.

capsid

the protein coat that covers the nucleic acid of a viral particle (virion)

10nm

the smallest virus is about how large?

-viridae

the suffix that represents a virus family

-virus

the suffix that represents the virus genus

Lysogenic infection

the type of infection where the virus inserts its DNA into the host cells genome. This cell is called a lysogen

helical

the virus shape that appears to be cylindrical, the capsomers are arranged in a helix

complex

the virus shape that had a more intricate structure, phages are the only viruses with this structure

icosahedral

the virus shape that has a 531 symetry, 20 small triangular facets.

lytic phages

these are virulent phages, they exit the host at the end of an infection lysing the cell. this type of infection is considered productive.

Temperate phages

these phages have the option of either directing a productive infection or incorporating their DNA into the host cell's genome (lysogenic infection). if the DNA is damaged the cell will go back into the lytic stage.

restriction modification systems

these protect bacteria from phage infection by quickly degrading incoming foreign DNA. They do this through restriction and modification enzymes.

integrase

this inserts the DNA into the cell chromosome in a lysogenic infection.

Chronic infections

this is a persistent infection characterized by continuous low level production of viral particles. (hep B, hep C, AIDS)

Latent Infection

this is a persistent infection where the viral genome (provirus) remains silent in the host cell, it can reactivate. (herpes, cyomegalovirus, HIV, epstein-barr virus)

Lysogen

this is the name of the cell where viral DNA has been integrated into its genome

generalized transduction

this results from packaging error during phage assembly. During packaging a piece of chromosome can be taken up instead of phage DNA. The piece of the chromosome can be taken up by a new host cell via homologous recombination

reverse transcriptase

this synthesizes DNA from the RNA template, it runs counter to the central dogma of molecular biology.

persistent infections

this type of infection can continue for years or even a lifetime. with or without symptoms

acute infections

this type of infection is charcterized by the sudden onset of symptoms and relatively short duration

naked virus

this type of virus is more resistant to disinfectants as it does not have an envelope.

retrovirus

this type of virus that has a +RNA genome and uses reverse transcriptase to make DNA from an RNA template.

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.

virion

viral particle that is made up of nucleic acid surrounded by a protein coat (capsid) ...a complete virus in its inert non-replicating form. also referred to as a viral particle

replicase

viraly encoded RNA, dependent on RNA polymerase that uses the RNA genome as a template to make complimentary copies

poison

virus means...

adenovirus

virus often used for gene replacement therapy,

lytic phage infection 5 step process

1. adsorption- this is where the phage attached to the cell. It binds to a receptor molecule 2. penetration- in prokaryotes only the nucleic acid penetrates the cell 3. gene expression and biosynthesis- the phage genome is transcribed and phage DNA is synthesized. 4. assembly- phage components are assembled 5. release- the progeny virus is released either through cell lysis or the new virus is extruded through the cell wall.

5 step process for the generalized infection cycle of animal viruses

1. attachment 2. penetration and uncoating- can be done via membrane fusion or endocytosis. the entire capsid is taken into the cell and it is then uncoated 3. gene expression and bisynthesis 4. assembly 5. release

repressor

a protein that prevents expression of the gene required for excision, it is essential for maintaining the lysogenic state.

cytopathic effect

a virus can cause the distinct morphological alterations in infected cells called....

enveloped viruses

a virus that has a bilayer envelope that surrounds the matrix protein

bacteriophages

a virus that infects a bacterial cell

tumor

abnormal growth of tissue resulting from a malfunction in the normally highly regulated process of cell growth.

malignant

abnormal mass of abnormal cells, can metastasize to other tissues

benign

abnormal mass of normal tissues, do not metastasize.

the viral genome

always either RNA or DNA but never both

prion

an infectious agent that causes a neurodegenerative disease; consists of protein similar in amino acid sequence to a normal protein. no nucleic acid, these are not viruses

lysogens

bacteria that carry prophage (phage DNA) in the genome.

oncogens

cells that can interfere with host control mechanisms and induce tumors

virus

genetic material surrounded by a protein coat, no metabolism, not alive,

Morphology of the virus

icosahedral, complex, and helical

replication of ssRNA

if you have the - strand you can make new genetic material right off the template, if not you have to make the - strand first.1