Transduction.

   Zinder  and  Lederberg  (Nobel 1958) placed two auxotrophic strains of
   Salmonella on opposite sides of a Davis U-tube.

   Prototrophs  were  recovered from the side containing LA-22 cells, but
   not from the side containing LA-2 cells.

   Adding   DNase,   an   enzyme   that  digests  DNA,  did  not  prevent
   recombination, so this is not transformation.

   The filter prevented cell contact, so this is not conjugation.

<LI> Recombination  stopped  when the pore size of the Davis U-tube was
reduced below the size of phages.
<li> This  transduction  was  mediated by phage P22, starting as a
prophage  in  LA-22  cells.  Rarely, some P22 enter the lytic
phase,  exit  the LA-22 cells, and cross the filter to infect
LA-2  cells.  When LA-2 cells are lysed, some LA-2 DNA may be