ON ASYMMETRY OF LAMBDA INTEGRATION SITES

This work suggests that the attachment regions of Escherichia coli and λ do not carry identical recognition sites. This hypothesis is consequent to an analysis of the lysogenization pattern of the bacteriophages λdg and λ. A new λ particle has been isolated in order to test further this formal proposal. This particle is capable of co-transducing the bacterial markers gal and bio (λdgb). The analysis of the lysogenization pattern of λdgb confirms and extends the suggested dissimilarity of E. coli and λ recognition sites. Another proposal is made, namely, that the excision of the λ prophage is not a simple reversal of the integration process. © 1969.