BSR Ch. 20 - Bacteriophages

What type of phage infection is characterized by a bacteriophage inserting DNA, and then replicating within the cell until the cell eventually lyses?

Lytic Infection

What type of phage infection is characterized by a bacteriophage inserting its DNA, and then the phage DNA incorporating itself into the host genome?

Lysogenic Infection

A phage whos DNA integrates into the host genome is called a lysogenic phage, also called a …?

Temperate phage

In its lysogenic state, a phage is called…?

Prophage

The bacteria containing a prophage is called a…?

Lysogen

When a lysogen experiences stress or severe damage, what does the prophage do?

Excise and become lytic

Who discovered lysogenic phages, and demonstrated that they could become lytic when the lysogen was exposed to UV light?

Andre Lwoff

What was the specific phage mentioned that could excise itself and become lytic after its host experienced UV damage?

phage lambda

In the lambda phage, what normally suppresses lytic genes?

CI dimer

After a lamba lysogen experiences UV damage, what causes cleavage of the CI dimer, inducing the lambda phage to become lytic?

RecA-ssDNA

What is it called when a lysogenic phage integrates into a bacterium and changes its behavior?

Lysogenic conversion

What is the name for regions of bacterial chromosomes that are of foreign origin, and contain clusters of genes usually associated with virulence?

Pathogenicity islands

What are the main indicators of a pathogenicity island?

GC% and codon usage

(T/F) Pathogenicity islands are neither prophages nor plasmids.

True

What S. aureus pathogenicity island carries the tst gene?

SaPI1

What is the tst gene?

Toxic shock syndrome toxin-1

SaPI1 can become parasitized and be packaged into tiny phage particles if what phage infects a S. aureus cell?

80alpha

What is the main acquired immune defense bacteria use against bacteriophages?

CRISPR/Cas

CRISPR stands for what?

Clustered Regularly Interspaced Short Palindromic Repeats

Cas in “CRISPR/Cas” stands for what?

CRISPR Associated

What proteins are responsible for cutting foreign phage DNA and integrating it into a specialized “library” to remember for subsequent infections?

Cas proteins

What are the 2 enzymes associated with bacterial innate immunity?

Restriction endonucleases and methyltransferases

What is the role of restriction endonucleases in bacterial innate immunity?

To recognize and cut specific sequences

What is the role of methyltransferases in bacterial innate immunity?

To methylate corresponding sequences to protect host genome from restriction endonucleases