Phages are collected from an infected E.coli donor strain of genotype ser⁺, gly⁺, leu⁺ and used to transduce a recipient of genotype ser^- , gly^- , leu^- . The treated recipient population is plated on a minimal medium supplemented with leucine and serine. Many colonies grew. Which one of the following combination of genotypes is appropriate for the colonies that grew ?