6.3 Bacteriophages

Vocabulary terms and definitions based on the lecture about bacteriophage structures, replication mechanisms, and quantification techniques.

Capsid

The head of a bacteriophage, formed as a 20-sided polygon (icosahedral) shape that contains either DNA or RNA for its genome.

Collar

The structure that attaches the capsid to the rest of the body of the phage and helps it sense its environment.

Sheath

A structure made of a contractile protein that produces a tube to move nucleic acids from the capsid into the host cell.

Base Plate

The structure at the base of a bacteriophage important for interacting with the host cell during infection.

Tail Fibers

Structures on a phage that initiate binding to specific protein receptors on the target cell membrane.

Lytic Replication

A replication pathway in bacteriophages that ends with the lysis and death of the host cell.

T4

An example of a lytic phage categorized by the letter T and an even number.

Direct Entry

An entry mechanism where the bacteriophage remains outside the host cell and injects its genome directly inside using its sheath like a hypodermic needle.

DNase

An enzyme contained in bacteriophages that cleaves and breaks down the host bacterial cell's DNA during replication.

Lysozyme

A protein encoded by the phage that functions to break down bacterial cell walls to lyse the cell and release newly assembled phages.

Lysogenic Pathway

A replication pathway where the phage genome integrates into the host cell's genome and is copied into daughter cells as the bacterial cell divides.

Temperate Phages

Phages that can utilize either the lytic or the lysogenic replication pathway.

Lambda Phages

An example of temperate phages that have the ability to utilize either the lytic or lysogenic pathway.

Prophage

The integrated phage genome within the host bacterial cell's genome during the lysogenic pathway.

Abandon Ship Strategy

The phenomenon where a prophage excises itself from the host genome when the bacterial cell undergoes stressors, allowing it to re-enter the lytic replication cycle before the host dies.

Viral Titer

Also referred to as the viral load, it is the quantified amount of viral particles present in a sample.

Turbidity

The measure of the cloudiness of a solution, which can be evaluated to measure viral titer or confirm a host bacterial strain.

Spectrophotometer

An instrument used to determine turbidity by measuring the absorbance and transmittance of light through a sample.