Microbiology: Viral Structure, Replication, and Pathogenesis

Vocabulary practice flashcards covering viral structure, genomic configurations, animal virus and bacteriophage replication cycles, cytopathic effects, and viral pathogenesis.

Segmented Genome

A viral genetic arrangement characterized by multiple individual pieces of nucleic acid, such as the influenza virus which contains seven separate pieces of RNA.

Positive-Sense RNA

Single-stranded viral RNA that can directly enter the host cell cytoplasm, bind to ribosomes, and be immediately translated into viral proteins.

Negative-Sense RNA

Single-stranded viral RNA that cannot be translated directly and must first be copied into a complementary positive-sense strand before translation can occur.

Reverse Transcriptase

An enzyme carried by retroviruses, such as HIV-1, that copies an RNA genome into a DNA molecule, reversing the standard direction of biological transcription.

Host Range

The specific spectrum of hosts a virus can infect, established by the interaction between viral surface components (spikes or fibers) and specific host cell receptors.

Tropism

Tissue specificity exhibited by a virus, where it targets only particular cell types within a susceptible host, such as Hepatitis B infecting specific types of human liver cells.

Budding

The exit mechanism employed by enveloped viruses in which assembled nucleocapsids interact with viral protein rafts on the host cell membrane and pinch off to form the enveloped virion.

Cytopathic Effects (CPEs)

Easily detectable virus-induced structural changes or damage to host cells, including altered size and shape, inclusion bodies, syncytia formation, and cell lysis.

Syncytium

A giant multinucleated supercell created when multiple host cells infected by certain viruses (such as RSV or herpesviruses) fuse their membranes together.

Negrae Bodies

Distinctive cytoplasmic inclusions formed in brain tissue that serve as a characteristic diagnostic hallmark of a rabies virus infection.

Chronic Latent Infection

A persistent viral infection in which the virus remains dormant and hidden in the host without producing active symptoms, interrupted by periodic symptomatic flare-ups.

Oncoviruses

Viruses equipped with oncogenes that possess the ability to push host cells out of the quiescent $G_0$ resting state and back into active cell division, driving tumor formation.

Neoplastic Transformation

The process by which viral infection induces host cells to grow abnormally where they are not supposed to, transforming normal tissues into cancerous cells.

Bacteriophage

A virus that infects bacteria by attaching to the cell wall and injecting only its nucleic acid into the cytoplasm, leaving its protein capsid structure on the outside.

Temperate Phage

A bacteriophage capable of choosing between an immediate lytic cycle or integrating into the host chromosome to establish lysogeny based on host physiological conditions.

Prophage

The viral DNA state of a temperate bacteriophage when it is integrated into the bacterial host chromosome during lysogeny.

Lysogenic Conversion

A phenomenon where a bacterium acquires new phenotypic traits or virulence factors—such as toxin production—conferred by genes present in an integrated prophage.

Plaque

A distinct, clear, unstained spot on a confluent lawn of cultured animal or bacterial cells where localized viral infection and replication have lysed and destroyed the host cells.

Superantigens

Pathogen-derived molecules that elicit an excessive, uncontrolled overreaction from the host immune system, frequently triggering massive inflammatory conditions.