is an intracellular bacteria and can't survive outside a bacteria alone.
-it reproduces rapidly.
What did Twort (1915) and D?Hérelle (1917) notice about a bacteria?
Bacterial cultures were lyzed when inoculated with fluids containing a virus.
**Bacteriophage = ?Bacteria eater?
**They discovered some bacteria will lyze. They realize that a virus causes the cell to lyze.
What are the 2 types of phages based on their life cycles?
*lytic and lysogenic
What is an example of the lytic phage?
T4 - the DNA that it injects is linear for the lytic phage whiles the DNA injected in the lysogenic phage is circular.
** in the Lytic phage, once the phage has pushed its DNA inside the bacteria, it hijacks the system and makes the DNA inside make RNA that will be used by the virus.
Sizes of the 2 phages:
lysogenic phage is smaller than lytic phage. Lysogenic phage is also called lambda.
Which of the phages have a complex life cycle?
Lysogenic, it is incorporated and almost silenced in the chromosome. It involves a lysogenic phage (a copy is integrated in the chromosome and remains silenced there. then later it will be lysed and expressed.
What are the ways to make a phage?
*Liquid culture-one bacteria lyses to form a lot of phage particles.
* Solid Medium-has nutrient.
What is the difference between a plaque and a colony?
**Plaque is cloning, start w/a single particle and make many.
**Colony is a large size group of organisms.
What are the 2 ways bacterial phenotypes can be determined.
Phenotypes: Lysis of bacteria
? Host range: A specific phage can only infect
specific strains of bacteria
? Plaque morphology: Large or small plaque,
function of speed of lysis
Fact: Wild type T?even (2,4,6?) phages can infect Escherichia coli strain B; however, T2 cannot infect Escherichia coli strain B/2 (mutant of B)
What affects B, B/2 and B/2 + B strain?
*Everything strain infects and forms plaque on the B strain. Everything is clear
*Only the mutant T2 can infect the mutant B strain (B/2). The mutant T2h is clear
** All can infect and form a plaque on the mixture, but the mutant will be turbid.
? Rapid lysis phenotype of T?even phages
? r+: small plaques with fuzzy edges
? r: large plaques with sharp edges
Can lead to offsprings that have the parent phenotypes at high freqs and recombinants at lower freqs.
How can you tell which ones are the recombinants?
The way to tell the recombinants is by inoculating B + B/2 cells because it will correspond to phenotypes.
what is recombination reciprocal?
Because we generate both h+r+ and h-r-. at the same freq. If only one shows up because the other is lethal, multiply by 2.