Escherichia coli Mutants Blocked in Lambda DNA Synthesis

Abstract

Both phage and bacterial genes are essential for replication of phage λ DNA. Lambda genes O and P are essential for phage DNA replication; mutants defective in either gene are able to replicate less than one round of DNA (Joyner et al., 1966; Ogawa and Tomizawa, 1968). It has been suggested that genes O and P code for an endonucleolytic activity that acts on λ DNA (Shuster and Weissbach, 1969; E. Jordan, personal communication). It is quite clear that λ replication requires in addition some host DNA synthesis functions, since λ is unable to grow in certain Escherichia coli mutants containing temperature-sensitive defects in DNA synthesis (Hirota et al., 1968; Kohiyama, 1968). In particular, Fangman and Feiss (1969) have reported that λ is unable to replicate at high temperature in a temperature-sensitive mutant of E. coli, FA22, which is defective in host DNA synthesis at 39°C.

Here we report the isolation and preliminary characterization of a class of E. coli mutants, called groP⁻, which are unable to propagate lambdoid phages. Evidence is presented (1) that the block in phage λ development is due to inability of the gene P product to function, and (2) that the groP⁻ bacteria are themselves conditionally defective in DNA synthesis. These results suggest that there is a functional association between the gene P product of phage λ and the host DNA synthesis system.

RESULTS AND DISCUSSION
Growth of lambdoid phages in bacterial mutants
Bacterial mutants (groP⁻) unable to support growth of λ and 434 were...