2 You perform a generalized transduction experiment where ph

2. You perform a generalized transduction experiment, where phages are collected from an S. aureus donor strain of genotype abc+ def+ ghi+, then used to transduce a recipient of genotype abc def ghi. The recipients were plated on minimal medium supplemented with def and ghi. You see lots of colonies

a) List the genotypes found in the colonies
b) Colonies are replicated onto three different media, (1) minimal plus ghi only, (2) minimal plus def only, (3) minimal. In theory, what genotypes would grow?
c) Growth was observed at 58% on medium 1, 7% growth was observed on medium 2, and no colonies observed on medium 3. What are the genotypes of the colonies on each medium?

Solution

a) Possible genotypes in the colonies

abc+ def+ ghi+ : abc def ghi : abc+ def- ghi- : abc+def-ghi+ : abc+def+ghi- : abc def ghi+ : abc def+ ghi+ :

abc def+ ghi

b) Colonies

(1) minimal plus ghi only

Genotypes that would grow : abc+def+ghi- and abc+ def+ ghi+

(2) minimal plus def only

Genotypes that would grow : abc+def-ghi+ and abc+ def+ ghi+

(3) minimal

Genotypes that would grow : abc+ def+ ghi+

c) Genotypes of the colonies on each medium

58% on medium 1 : abc+def+ghi-

7% growth on medium 2 : abc+def-ghi+

no colonies on medium 3 because growth cannot happen with these genotypes: abc def ghi : abc+ def- ghi- : abc def ghi+ : abc def+ ghi+ : abc def+ ghi

So transduction has taken place which accounts for 58% of colonies with genotype abc+def+ghi-  and 7% of the colonies with genotype abc+def-ghi+