Chapter 18, Problem 10EQ

This question combines your knowledge of bacterial conjugation (described in Chapter 7) and the genetic regulation that directs the phage $\lambda$

reproductive cycles. When researchers mix donor Hfr strains with recipient ${\text{F}}^{–}$

bacteria that are lysogenic for phag $\lambda$, the conjugated cells survive normally. However, if donor Hfr strains that are lysogenic for phage $\lambda$

conjugate with recipient ${\text{F}}^{–}$

bacteria that do not contain any phag $\lambda$, the recipient cells often lyse, due to the induction of $\lambda$

into the lytic cycle. Based on your knowledge of the regulation of the two reproductive cycles of phage $\lambda$, explain this experimental observation.