Chromosome Mapping of Pasteurella pseudotuberculosis by Interrupted Mating

Pasteurella pseudotuberculosis , containing theEscherichia coli plasmid F′lac , transferred its chromosome in an oriented manner to each of five multiply auxotrophic strains ofP. pseudotuberculosis . In a mating system containing gelatin, glucose, and phosphate buffer, a maximum of 0.02% of the donor cells transferred lead markers. The donor population was counterselected with nalidixic acid. We established the entry time of seven markers as follows: proline (11 min); arginine (14 min); histidine (14 min); threonine (25 min); lysine (50 min); tyrosine (67 min); and tryptophan (77 min). However, an analysis of the inheritance of unselected markers did not support the simplest assumption that the chromosome was transferred as Origin...pro... arg his... thr... lys... tyr... trp .... The markers common to all five recipients,arg andhis , were closely linked, but of the five other markers, each unique to a different recipient strain, onlytrp was linked toarg andhis . Our data suggest that thePasteurella chromosome is transferred in more than one linkage group.