R transfer toS. panama in vitro and in vivo

Thein-vitro and thein-vivo transfer frequencies ofE.coli 50 (R1) carrying a phage-restricting R factor, and ofE.coli 71 (R2) carrying a non-restricting R factor, were measured. Thein-vitro transfer frequencies were found to be greatly dependent on the method of conjugation employed. The transfer,in vivo, of R factor R2 toS.panama was slightly more efficient than was the transfer of R1.