[Plasmid determined lactose positive character in (Enterobacter hafniae) and (Proteus morganii) (author's transl)].

The atypical lactose positive characters have been found to be plasmidmediated in 6 strains of Enterobacter hafniae and 2 strains of Proteus morganii. One of the P. morganii plasmid possesses the fi+ character, all the other plasmids belonging to the fi-group. Both plasmids of P. morganii could be transduced and remained then readily transferably by conjugation. Two of the E. hafniae plasmids were found unstable when harboured in Salmonella typhi grown at 40 degrees centigrade, when they were stable in the same strain grown at 37 degrees. The other plasmids were stable in the original strains, in S. typhi, in Escherichia coli both at 37 degrees and 40 degrees. These results are discussed according to investigation about (lactose plasmids) of which a bibliographic review is presented here.