Recombination Between a Thermosensitive Kanamycin Resistance Factor and a Nonthermosensitive Multiple-Drug Resistance Factor

AUTOR(ES)

Yokota, Takeshi

RESUMO

The thermosensitive kanamycin (KM) resistance factor, R(KM)t, and a nonthermosensitive multiple-drug resistance factor, R100, were simultaneously introduced into Escherichia coli and Salmonella typhimurium. The temperature sensitivity of both R factors remained unchanged as long as they replicated independently. Under certain conditions, however, a new thermosensitive R factor harboring resistance markers for kanamycin, streptomycin (SM), and sulfanilamide (SA) was obtained by recombination between the R(KM)t and R100 factors. R factors carrying resistance markers for KM and SA, or for SM and SA, were obtained from the recombinant R(KM SA SM)t by spontaneous segregation. Though the R100 factor has been known as an fi+ (positive for F-mediated fertility inhibition of its host) type and it does not restrict any coexisting phages, the thermosensitive recombinants of R100 with R(KM)t and their segregants were found to be fi− and to restrict the replication of all T-even phages, as does the R(KM)t factor. Double infection immunity was not observed between the R(KM)t and R100 factors.

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