Fourteen strains belonging to the genera
Rhizobium, Bradyrhizobium and
Agrobacterium were investigated for susceptibility to infection by a lysogenic phage (phage φU) from
Rhizobium leguminosarum biovar
trifolii. All strains tested were resistant to phage φU infection; however, the phage was able to adsorb to
R. leguminosarum biovar
viciae strain K5. Plasmid pCI6 carrying the attachment site (
attP) of phage φU was introduced into all these strains by conjugation. The tetracycline resistance (Tc
r) gene on pCI6 was used as a selectable marker. When
R. leguminosarum biovar
viciae strain K5 was used as a recipient, Tc
r transconjugants appeared at high frequency (4.41×10
-3). Southern hybridization with the
attP fragment of phage φU indicates that pCI6 is integrated into the chromosome of 10 transconjugants. Furthermore, the restriction map of pCI6 integration region on the chromosome of strain K5 was shown to be identical to that of
R. leguminosarum biovar
trifolii strain 4S which was the original host strain of phage φU.
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