E2 - Viruses

Bacteriophage

Viruses that infect bacteria - Complex structure - Most contain dsDNA

Budding

Occurs when enveloped viruses assemble the nucleoid capsule along the membrane and ‘bleb’ off and out of the cell - Steals lipids in the process

Capsid

Viral Component - Protein that holds the core

Capsomeres

Individual proteins that make up the Capsid

Complex Capsid

Capsid that looks like alien - Only seen in bacteriophages - Structure to help penetrate peptidoglycan layer in bacteria to inject nucleic acid

Crisper-Cas

A prokaryotic “immune system” that evades viral destruction and maintains genome stability - Consists of Spacers, Cas Proteins, and crRNAs - In Bacteria and Archaea - Prokaryotic Immune Memory

Helical Capsid

Rod shaped capsid - Can sometimes get encapsulated into an envelope

Host Range

Defines type of organism that virus will infect - Determined by if organism and virus has specific receptors

Icosahedral Capsid

Capsid that has perfect symmetry

Integrase

A key enzyme in Retroviruses - Enzyme that helps integrate viral DNA into the host DNA

Latent Infection

A result of animal virus infections - Cell is continuously infected, but there may be period of time where nothing is happening (no/low levels of viruses being released) - Can switch back to a Lytic infection

Lysis

the disintegration of a cell by rupture of the cell wall or membrane - Occurs in the Lytic pathway resulting in cell death

Lysogenic Conversion

Lysogenized bacteria undergo this resulting in a phage being inside it

Lysogeny

State where most virus genes are no expressed and virus genome (prophage) is replicated in synchrony with host chromosome 

Lytic Pathway

Virulent Mode - Viruses lyse host cells after infection

Negative Sense RNA

Form of RNA that cannot be directly translated into proteins - Has to make positive sense RNA strands to make Protein and more of this type of RNA

Nucleocapsid

Key viral enzymes are found with this (RNA dependent polymerases, Reverse transcriptase) - Complex of RNA or DNA and Proteins that form the core of some viruses

Obligate Intracellular Parasite

Cannot multiply unless they invade a specific host cell and instruct the hosts genetic and metabolic machinery to make and release new viruses (need to be inside other cells)

Oncogenic

Transformation of cells - ? viruses

Oncovirus

Viruses that transform the host cell into becoming a ‘tumor cell’ - cell keeps dividing can every time makes more virus - cancer causing virus

Persistent Infection

Result of animal virus infection - Virus slowly buds out, not killing the cell, but continuous to hide out in the cell making more viruses

Phage

Term reserved for bacteria viruses (not bacteriophage)

Plaque

Form in culture plates when trying to grow bacteria - Area where bacteria has been lysed and where bacteriophages can be found - This can be counted to determine number of phages present

Positive Sense RNA

Type of RNA that can directly go into translation of a protein

Prion

Proteinaceous infectious particle - Not all cause disease - Inherited and transmitted by ingestion, transplant, and surgical instruments - Found in all domains of life

Prophage

Virus genome in the progeny after replication

Restriction Enzyme

Cleave DNA at specific sequences - Watch out for a specific sequence to cleave - Will ONLY cleave and recognize unmethylated DNA

Retrovirus

ssRNA virus - Has 2 indentical ss(+) RNA - Gets converted into DNA with reverse transcriptase then integrates itself into host DNA, Replicates with host DNA - Hard virus to cure (ex: HIV)

Reverse Transcriptase

A key enzyme of retroviruses - Enzyme that converts retroviruses into DNA so it can be integrated into the host cells DNA

RNA Dependent RNA Polymerase

Enzyme that catalyzes the replication of RNA from an RNA template - important enzyme for RNA viruses

Spongiform Encephalopathy

Prion that causes Sheep scrapie, Creutzfeldt-Jakob disease, Mad Cow disease, Chronic Wasting Disease - Causes holes to form in the brain eventually leading to loss of body control - always fatal

Temperate Phage

Bacteria virus that replicates their genome with the host genome - Does not kill host cell - The mode this virus is in is known as a state of Lysogeny

Transformation

Result of animal viral infection: Oncogenic viruses do this - turn host cell into becoming tumor cell

Viral Envelope

Lipid bilayer that viruses steal from their host cell - Acts as an extra protective layer - Not all viruses have this - Found in some animal viruses

Viral Spikes

Protein/Enzymes found in/on envelope/capsid - Cleave host proteins, Aid in attachment/release, Aid in immune evasion - Viruses that have these referred to ‘naked’ virus (no outside envelope)

Viral Titer

Number of infectious units per volume of fluid - Involved in Culturing/Growing viruses

Virion

Name for obligate intracellular parasites - The complete infective form of a virus outside the host cell

Viroid

Infectious RNA molecules that lack a protein coat - Smallest known pathogens - Small, circular, ssRNA molecules - Cause many important plant diseases - Do not encode proteins, completely dependent on host-encoded enzymes - (literally just pieces of infectious RNA)

Virulent Infection

Result of animal viral infection - Causes lysis death of host cell - Most viruses

Virus

Non-living infectious particles - Either active or inactive - Do not have cells - Obligate intracellular parasites

Core

Viral component - genetic material (DNA or RNA)

Highly specific

Attachment of virion to host cell is ?

DNA viruses

Type of virus that enters host cell’s nucleus where they are replicated and assembled - Some bring their own polymerases and some dont

RNA viruses

Type of virus that is replicated and assembled in the nucleus and/or cytoplasm - Must have their own RNA dependent polymerases or reverse transcriptase

Host cell lysis, Budding (results in envelope)

2 Ways Animal viruses can be released from host cell

Lysogenized bacteria

These phage infections can contribute to disease by supplying toxin genes - Ex: Bacteria is not infectious until phage comes in and supplies a gene that makes it now infectious

Restriction Modification system

Type of Prokaryotic ‘immune system’ - DNA destruction system - Effective only against dsDNA viruses - Use restriction enzymes to cleave specific unmethylated DNA sequences

One step curve

Name of virus growth curve

Burst size

Number or virions released

Plaque Assay

Analogous to bacterial colony - One way to measure virus infectivity