Viruses, Viroids, and Prions Unit 3

Flashcards covering key vocabulary terms related to viruses, viroids, and prions from the microbiology lecture.

Virus (Louis Pasteur)

Term proposed by Louis Pasteur, meaning 'poison'.

Virus (General Characteristic)

Genetic information (DNA or RNA) contained within a protective protein coat; non-living entities that cannot multiply independently of a host cell.

Non-living entities (Viruses)

Cannot exist independently from the host cell and are not considered organisms.

Animal viruses

Viruses that infect animal cells.

Plant viruses

Viruses that infect plant cells.

Bacteriophage

Viruses that infect bacteria.

Virion

A complete viral particle, consisting of nucleic acid surrounded by a capsid.

Capsid

The protective protein coat surrounding the nucleic acid of a virus.

Capsomeres

Simple, identical subunits that compose the capsid of a virus.

Nucleocapsid

The capsid together with the nucleic acids of a virus.

Spikes

Viral structures that attach to receptor sites on host cells.

Enveloped viruses

Viruses surrounded by a lipid bilayer obtained from the host cell.

Matrix protein

A protein layer found between the nucleocapsid and the envelope in enveloped viruses.

Non-enveloped (naked) viruses

Viruses that lack an outer lipid envelope, making them more resistant to disinfectants.

Icosahedral

A common virus shape characterized by 20 flat triangular faces.

Helical (virus shape)

A virus shape where capsomeres are arranged in a helix.

Complex viruses

Viruses with complicated structures, such as a bacteriophage with an icosahedral head and a helical tail.

Viral genome

Contains a single type of nucleic acid (either DNA or RNA, never both), which can be linear or circular, single-stranded or double-stranded.

Extracellular phase (Viruses)

The metabolically inert phase of a virus, existing outside a host cell.

Intracellular phase (Viruses)

The metabolically active phase of a virus, existing inside a host cell and utilizing its machinery for reproduction.

Lytic Cycle

An infection cycle where virulent phages exit the host cell by lysing and thereby killing the cell.

Virulent phages

Bacteriophages that undergo a lytic replication cycle, destroying the host cell.

Lysogenic Infection

An infection where phage DNA integrates into the host chromosome as a prophage, replicating along with the host.

Prophage

Integrated phage DNA within a bacterial host chromosome during a lysogenic infection.

Lysogen

A bacterial cell carrying an integrated prophage.

Transduction

Horizontal gene transfer in bacteria resulting from an excision mistake or packaging error during phage replication, leading to bacterial DNA being packaged into phage heads.

Transduction particle

A phage head that mistakenly carries bacterial DNA instead of phage DNA, capable of transferring it to a new host.

Host range (Viruses)

The number of different host cells that a virus can infect, typically limited by host cell receptors.

Enteric viruses

Viruses generally transmitted via the fecal-oral route, often causing gastroenteritis.

Respiratory viruses

Viruses usually inhaled via infected respiratory droplets, generally remaining localized in the respiratory tract.

Zoonotic viruses

Viruses transmitted from animals to humans via an animal vector.

Sexually transmitted viruses

Viruses that can cause lesions on genitalia or systemic infections, spread through sexual contact.

Balanced pathogenicity

A relationship between viruses and normal hosts where no obvious disease or damage is caused.

Acute Infections (Viruses)

Viral infections that are usually short in duration, where host cells often die and release virions, and the host may develop long-lasting immunity.

Persistent infections (Viruses)

Viral infections where the virus continually remains present in the host, releasing from infected cells via budding, and can be categorized as latent, chronic, or slow.

Latent infections

A type of persistent infection characterized by a symptomless period followed by reactivation, where infectious particles are not detected until reactivation.

Chronic infections

A type of persistent infection where infectious virus can be detected at all times, and disease may be present or absent during extended periods.

Slow infections

A type of persistent infection where the infectious agent gradually increases in amount over a long period with no significant symptoms apparent initially.

Tumor viruses

Viruses, primarily double-stranded DNA viruses, responsible for most virus-induced tumors in humans, by transforming cells without killing them.

Transformed genes (in cancer)

Viral genes expressed after integration into host DNA, leading to abnormal cell growth and tumor formation.

Oncolytic viruses

Viruses that specifically target and kill cancer cells, either directly by causing lysis or indirectly by stimulating the host\u2019s immune cells.

Primary culture (for viruses)

A tissue culture prepared directly from an animal host, used for cultivating viruses.

Plant viruses

Viruses that cause various plant diseases, often recognized by pigment loss, marks on leaves and fruit, tumors, or stunted growth.

Plasmodesmata

Openings in plant cell walls through which plant viral infections can spread from cell to cell.

Viroids

Small, single-stranded RNA molecules that form a closed ring, known pathogens found only in plants, much smaller and distinctly different from viruses.

Prions

Proteinaceous infectious agents composed solely of protein with no nucleic acids, linked to slow, fatal brain degenerating diseases (transmissible spongiform encephalopathies).

Transmissible spongiform encephalopathies (TSEs)

A group of fatal brain diseases caused by prions, characterized by brain tissue developing sponge-like holes, often with symptoms appearing years after infection.

Prion proteins (Accumulation effects)

Accumulation of prion proteins in neural tissue leads to neuron death, development of holes in brain tissue, and deterioration of brain function, characteristic of TSEs.