MCB3020 Week 7: Viruses & Eukaryotes

Virus

A genetic element that cannot replicate independently of a living host cell

Virus particle

Extracellular form of a virus, allows viruses to exist outside of the host and facilitates transmission from one host cell to another

Virion

Infectious virus particle; nucleic acid genome surrounded by a protein coat and sometimes other layers of material

Capsid

The protein shell surrounding the genome of a virus particle

Capsomer

Small proteins that make up the capsid

Nucleocapsid

Nucleic acid and protein packaged in the virion (nucleic acid and capsid)

Enveloped virus

Virus containing additional layers around the nucleocapsid, lipid bilayer with embedded proteins with some of the embedded proteins being glycoproteins which are encodedby the viral genome- made by host cell machinery

Helical symmetry

Rod-shaped virus

Icosahedral symmetry

Spherical virus

Complex viruses

Virions composed of several parts that have separate shapes/symmetries

Critical enzymes

For infection, these are _; lysozyme, nucleic acid polymerases, and neuraminadases; only found in some virions

Nucleic acid polymerase

Enzyme critical to infection found in some virions, capable of performing reverse transcriptase

Neuraminadases

Enzyme critical to infection found in some virions, enzymes that cleave glycosidic bonds that allows for liberation of viruses from host

Virus quantification

This can be determined depending on what type of organism it is; bacterial viruses can be grown in model systems, animal viruses can be cultivated in tissue or cell cultures, plant viruses need the growth of the entire plant

Titer

Number of infectious units per volume of fluid

Plaque assay

One of the most accurate ways to measure virus infectivity, analogous to the bacterial colony

Plaque

Clear zone that develops on lawns of host cells when carrying out a plaque assay

Attachment/adsorption

First step of viral replication, the virus finds a susceptible host cell

Entry/penetration

Second step of viral replication, the virion or nucleic acid enters the host cell

Synthesis

Third step of viral replication, the virus nucleic acid and protein are created by cell metabolism as redirected by the virus

Assembly

Fourth step of viral replication, the capsids and viral genomes are packaged into new virions (maturation)

Release

Fifth and final step of viral replication, the virions leave the host cell

Eclipse

Stage in the virus life cycle where genome is replicated and proteins are translated

Maturation

Stage in the virus life cycle where nucleic acids are packaged in capsids

Latent period

Eclipse + Maturation

Receptors

Attachment of the virion to a host cell is highly specific and requires complementary _ on the surface of the host and its infecting virus; these carry out normal functions for the cell and includes proteins, carbohydrates, glycoproteins, lipoproteins, or complexes

Bacteriophage T4

Virus of E. coli that has one of the most complex penetration mechanisms where the tail fibers attach to polysaccharides on the E. coli, then the tail fibers retract and the tail core makes contact with the E. coli cell wall and the T4 genome enters thru the tail lysozyme

Restriction-modification systems

Employed by many bacteria to evade viral infection; acts as a DNA destruction system that uses restriction enzymes to cleave DNA at specific sequences

Positive-strand RNA virus

Single-stranded RNA genome with the same orientation as its mRNA, being in its + configuration

Negative-strand RNA virus

Single-stranded RNA genome with complementary orientation to it's mRNA, being in its - configuration

RNA-dependent RNA polymerase

Needed by negative stranded RNA and double-stranded RNA viruses to make mRNA

Early proteins

Apart of the T4 genome, enzymes needed for DNA replication and transcription

Middle/late proteins

Apart of the T4 genome, head and tail proteins and enzymes required to liberate mature phage particles

Bacteriophages

Diverse group of viruses that mostly infect enteric bacteria, most contain dsDNA genomes

Virulent mode

Viral life cycle where viruses lyse host cells after infection

Temperate mode

Viral life cycle where viruses replicate their genomes in tandem with host genome without killing the host

Temperate viruses

Undergoes a different life cycle resulting in a stable genetic relationship with the host but can also kill cells through the lytic cycle

Lysogeny

State where most virus genes not expressed and virus genes/genome is replicated along with the host chromosome

Prophage

A viruses genes/genome, found in lysogens

Lysogen

A bacterium containing a prophage

Enveloped animal viruses

Many more kinds of ____ exist than bacterial viruses; as these leave the host cell, they can remove part of the host cell's lipid bilayer for their envelope

Persistent infections

Consequence of virus infection in animal cells where the release of virions from host cell does not result in cell lysis where the infected cell remains alive and continues to produce virus indefinitely

Latent infections

Consequence of virus infection in animal cells where there's a delay between infection by the virus and lytic events

Transformation

Consequence of virus infection in animal cells where the normal cell is converted into a tumor cell

Retrovirus

RNA viruses that replicate using a DNA intermediate, enveloped virus that contains a reverse transcriptase, integrase, and protease

Reverse transcriptase

Found in retroviruses, copies information from its RNA genome into DNA

Integrase

Found in retroviruses, integration of retroviral DNA into host genome

Protease

Found in retroviruses, cleaves large proteins into smaller individual proteins to be used as viral particles

Prion

Infectious protein known to cause disease in animals, results in neurological symptoms, can be obtained infectiously, sporadically, or inherited

Infectious prion disease

Pathogenic form of prion protein transmitted between animals or humans

Sporadic prion disease

Random misfolding of a normal, healthy prion protein in an uninfected individual

Inherited prion disease

Mutation in prion gene yields a protein that changes more often into disease-causing form

Mitochrondrion

Respiration and oxidative phosphorylation, organelle

Hydrogenosome

Lacks citric acid cycle enzymes and cristae, no e- transport chain and no genome of its own, oxidizes pyruvate -> H2, CO2, acetate, organelle

Chloroplast

Phototrophic organelle, contains thylakoids, stroma, rubisco

Thylakoids

Flattened membrane discs found in chloroplasts

Stroma

Lumen of the chloroplast, contains large amounts of rubisco which is useful for the Calvin cycle

Rubisco

Key enzyme of the Calvin cycle found in the stroma of chloroplasts

Diplomonads

Protist, has two nuclei of equal size, key genus giardia is the cause of giardiasis- a common waterborne disease

Giardia

Key genus of Diplomonads that causes giardiasis, a common waterborne disease

Parabasalids

Protist, key genus is Trichomonas vaginalis, found in intestinal and urogenital tract

Euglenozoans

Key genera are trypanosoma and euglena, unicellular flagellated eukaryotes that include Kinetoplastids who live primarily in aquatic habitats, some can cause serious disease in humans

Kinetoplastids

Group of Euglenozoans that are named for the presence of the kinetoplast which is a mass of DNA in single, large mitochondrion; these live primarily in aquatic habitats feeding on bacteria

Trypanosoma brucei

Euglenozoan, African sleeping sickness transmitted by the tsetse fly

Euglenids

Euglenozoan, nonpathogenic and phototrophic organisms that feed on bacteria by phagocytosis

Alveolates

Contains alveoli that are sacs underneath the cytoplasmic membrane, members include ciliates, dinoflagellates, and apicomplexans

Ciliates

Alveolate, has two nuclei with one being a macronuclei and the other a micronuclei, common species is paramecium

Dinoflagellates

Alveolate, phototrophic marine/freshwater organisms, dense suspensions of some species can cause harmful algal blooms (HABs) with Karenia brevis being a representative as the red tide organism

Apicomplexans

Alveolate, contains apicoplasts that degenerate chloroplasts, obligate parasites of animals that cause severe diseases, malaria (P. falciparum) is the worst followed by Toxoplasma gondii and Cyclosporiasis

Malaria

Apicomplexan virus named Plasmodium falciparum, starts with mosquito biting an infected person which then infects the liver and red blood cells

Toxoplasma gondii

Apicomplexan virus that starts with the cat being contaminated by hunting which spreads to raw or undercooked meat, contaminated water and veggies or contact with cat feces, 1st exposure during pregnancy is fatal for a fetus

Stramenophiles

Includes oomycetes, diatoms, golden algae, and brown algae with oomycetes being water molds based on filamentous growth and coenocytic hyphae

Amoebozoa

Terrestrial and aquatic protists that use pseudopodia for movement and feeding, major groups include gymnamoebas, entamoebas, and slime molds

Gymnamoebas

Amoebozoa, moves by amoeboid movement and are free living creatures that inhabit soil and aquatic environments

Entamoebas

Amoebozoa, lives in oral cavity and intestinal tract, parasites, entaboeba histolytica is a notable species that is a pathogen causing bloody diarrhea

Slime molds

Amoebozoa, similar life cycle to fungi, motile and can move across surfaces rapidly, two groups are plasmodial and cellular

Microsporidia

Unicellular obligate parasites from fungi that often infect immuno-compromised individuals

Unicellular red algae

Also known as rhodophytes, they get their color from phycoerythrin

Unicellular green algae

Key genus Volvox, also called chlorophytes