Explanations accounting for transduction by bacteriophage lambda in maltose negative bacteriophage lambda resistant mutants of Escherichia coli K-12.

Entry of DNA from lambda phages particles into lambdarMAl- mutants of Escherichia coli K-12 is shown to be due to two distinguishable processes. One, residual transduction, results from a low level expression of lamB. The other one, background transduction, is independent of gene lamB. Interpretations are presented for these results. It is propos that residual transduction is due to a weak promoter pB3 located within or near the distal part of the gene preceeding lamB in the same operon. It is proposed that background transduction is due to a secondary receptor structure for phage lambda. Finally a tentative hypothesis relatin pB3 to insertion sequences is presented.