The genome of Salmonelln typhi was cut with Ceu I(which cuts in the rrn operons, encoding ribosomal RNA) and the fragments mapped by a combination of (a) probing Ceu I bands with Bln I fragments, to detect adjacent Ceu I fragments, (b) probing Bln I bands with Ceu I fragments, to confirm the data obtained using Bln I fragments as probes, and (c) partial Ceu I digestion. Seven Ceu I framgnets were placed on a circular map....[ Read more ]

The genome of Salmonelln typhi was cut with Ceu I(which cuts in the rrn operons, encoding ribosomal RNA) and the fragments mapped by a combination of (a) probing Ceu I bands with Bln I fragments, to detect adjacent Ceu I fragments, (b) probing Bln I bands with Ceu I fragments, to confirm the data obtained using Bln I fragments as probes, and (c) partial Ceu I digestion. Seven Ceu I framgnets were placed on a circular map.

Five cosmids, containing cloned DNA from S.typhi which did not have homologous sequences in Snlmonella typhimurium, were isolated, and the S.typhi- unique DNA localized on the Ceu I restrictiion map. This DNA may bear genes contributing to the human-specificity of S.typhi infection.

Comparision of the S.typhi map obtained with published maps of S.typhimurium and Escherichia coli K-12 showed, that while all 3 genomes had the same number of Ceu I fragments, S.typhi differed from the other 2 strains in the arrangment of the homologous fragments. This suggests that S.typhi and S.typhimurium are not closely related. Thus: E.coli K-12 is more closely related to S.typhimurium than is S.typhi.