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Five mutants (called tnm) of Escherichia coli with impaired ability for transposition of Tn9 were isolated after treatment with ethyl methanesulfonate (EMS) or N-methyl-N'-nitro-N-nitrosoguanidine (NG). The map locations of the tnm mutations were determined by a combination of Hfr matings, F' episome complementation and P1 transductional mapping. The data obtained show that the five tnm mutations are located near 91 min on the Escherichia coli linkage map and are cotransducible with the metA marker with a frequency of 3%-4%. Introduction of F' plasmids containing this region complements the Tnm- phenotype for the two mutants tested i.e. tnm-1 and tnm-2 are recessive in tnm+/tnm- merodiploids.

The genome of lambda phage with thermosensitive repressor was inserted into the pts region of the Escherichia coli chromosome. This lysogenic culture possessed the PTS1 phenotype at 30 degrees C. A mutant strain with a deletion covering the ptsH gene was isolated after a prophage curing procedure. The deletion nature of the pts mutation was confirmed in genetical and biochemical experiments. The deletion covered a small fragment of the bacterial genome not extending in the ptsI and lig genes. The isolated deltaptsH mutant possessed all characteristics of known pts mutants: pleiotropical disturbances of transport and utilization of a number of carbohydrates, repression of the enzyme inducible synthesis, and resistance to glucose catabolite repression. From these and other data we can conclude that the phosphorylated form of the heat-stable protein HPr is involved (directly or indirectly) in activation of the DNA transcription process.