Bacteriophage Lifecycles and Viral Replication Notes

Vocabulary flashcards covering viral lifecycle stages, growth curves, phage T4 mechanisms, lysogeny, host prokaryotic defenses, and animal virus outcomes based on Chapter 1-6 lecture transcripts.

Plaque-forming units (PFUs)

The unit of measurement used to quantify infectious phages by observing clear zones where host cells fail to grow on a plate.

Eclipse period

The phase in a viral growth curve during which no complete virions or PFUs are detected because viral nucleic acids and proteins are being synthesized.

Maturation period

The stage in a viral growth curve following the eclipse phase where newly synthesized nucleic acids and capsid proteins assemble into complete virions.

Burst size

The total number of mature virions produced and released from a single host cell during a viral infection.

Early proteins

Enzymes synthesized shortly after viral penetration that function in viral nucleic acid replication and modify host RNA polymerase to express viral genes.

Late proteins

Structural proteins synthesized toward the end of infection, including capsid head and tail components as well as enzymes needed for cell lysis.

Prohead

An empty capsid structure formed during viral assembly before the viral genome is packaged into it.

Terminase motor

A motor protein complex that utilizes host ATP to pack and compress viral genomic DNA into the prohead shell.

Virulent phage

A bacteriophage, such as T4, that strictly follows the lytic cycle, continuously producing virions and causing host cell lysis.

Temperate phage

A bacteriophage, such as Lambda, capable of either initiating a lytic infection or integrating its genome into the host chromosome via lysogeny.

Lysogenic cycle

A viral lifecycle phase where the injected phage genome integrates into the host chromosome and replicates stably alongside host cell division.

Prophage

The viral DNA genome when it is stably integrated into the host bacterial chromosome during lysogeny.

Induction

The process where inactivation of a phage repressor protein—often triggered by host cell DNA damage—causes a prophage to exit lysogeny and enter the lytic cycle.

CRISPR system

A prokaryotic defense system that integrates foreign nucleic acid fragments into its genome to produce RNAs that target and cleave matching incoming viral DNA.

Restriction enzymes

Biological catalysts present in host prokaryotes that recognize and cleave specific DNA sequences to prevent viral infection.

Uncoating

The step during animal virus entry where the outer lipid envelope or capsid breaks down to release the nucleocapsid or viral genome into the host cell cytoplasm.

Persistent infection

An outcome of animal virus infection where host cells slowly release viral particles by budding without immediate cell death or lysis.

Transformation

An infection outcome in animal cells where viral integration or gene expression alters the host cell into a cancerous state.