Intergeneric conjugation in Thiobacillus versutus

In plate matings with Escherichia coli HB101/pUW965::Tn5 (KmR) Thiobacillus versutus reacted as an efficient recipient, producing 10(-2) to 10(-3) kanamycin resistant (KmR) T. versutus exconjugants per donor cell. Analysis of agarose gels of plasmid DNA extracted from the exconjugants confirmed that the suicide vector pUW964 did not persist in the recipient, implying that the kanamycin resistance of the exconjugants is based on effective transposition of Tn5 in T. versutus as well as function of the E. coli kanamycin gene. Transfer was equally efficient when a nalidixate-resistant T. versutus mutant was used as recipient. Hybridization evidence for the presence of Tn5 was consistently negative. The significance of this anomalous result is discussed.