The isolation of λ transducing phages carrying the tolPAB cluster is described. These genes map between gltA and gal in Escherichia coli, and thus are relatively close to attλ. To isolate these transducing phages, it was necessary to use a strain deleted of most of the intervening genes (nadA to chlD) between tolPAB and attλ. Using a lysogen of such a deletion strain, several defective λdtol phages were isolated that carry different amounts of the tolPAB cluster.

A colicin-tolerant mutant of Escherichia coli which is temperature-dependent for tolerance and unable to grow at 40° without the addition of salt, plates λ+ wild-type phage with a reduced frequency and very turbid plaques at 30°, failing to form any plaques at 40° even though the cells become phage infected. Phage mutants λcI, λcII, λcY42 and λvir form clear plaques and plate with equal efficiency on the mutant and its parent strain at both temperatures. The results show that over 95% of the phage infected cells become lysogenized after λ+ phage infection. In contrast, the temperate phage P1 formed normal turbid plaques with equal frequency on both bacterial strains, but phage ϕ80 forms normal turbid plaques at 30° and clear (non-lysogenic) plaques at 40°. An investigation of the mutant strain showed that it not only lacked a large molecular weight component from its cell envelope but also had reduced capacity to synthesize cyclic-3′,5′-AMP. It is proposed that the mutation(s) in the colicin-tolerant mutant gives rise to a number of alterations, one of which changes the cell envelope and leads to the reduction of intracellular cyclic AMP and the other giving rise to an altered RNA polymerase specificity. These alterations lead to a changed ratio of the products of the λ-genes involved in the control of lysogeny and give rise to a bias towards the lysogenic response. The cIII gene product of λ is not as essential to lysogeny as cII or cI and therefore possibly acts as an internal control of other λ functions (e.g. cro).

A method was devised to isolate mutants carrying deletions through several genetic loci (chlD (+) andchlA (+)) which are involved in the membrane-bound nitrate respiratory complex ofEscherichia coli. Specific λ transducing phages were used to reintroduce these genes. Comparisons of membrane fractions from these transduced strains showed five membrane proteins that are necessary for the formation of an active nitrate respiration system. Two particular bacterial genes (chlD (+) andchlA (+)) were shown to control these five membrane proteins.Three of the proteins specified bychlA (+), appear to be constitutively controlled and always present in the membrane ofE. coli irrespective of growth conditions, while the other two proteins, specified bychlD (+), appear to be induced byanaerobic growth in the presence of nitrate.

Mutants of the bacteriophage lambda have been isolated which can form plaques as well as transduce a series of bacterial loci. Included amongst the loci carried by the phages are the chlA genes which control membrane components involved in the nitrate respiration complex of E. coli. By using the appropriate chlA deletion mutants and λpchlA phage, it was possible to transduce control of formic dehydrogenase activity with the chlA genetic locus.

Deletion mutants extending from tol A,B to chl A of E. coli K12 were isolated and characterized. Physiological studies indicate that these mutants show sensitivity to a wide range of antibiotics and detergents, indicating an alteration of the cell envelope. Analysis by polyacrylamide gel electrophoresis demonstrated the loss of membrane proteins in the deletion mutants of this genetic region.