Double Infection, Recombination, and Segregation of Two R Factors, R100 and Rts1, and Their Possible Bearing- on the- Genetic Structure of R100

Abstract

Applying the observation by Yokota et al (1969) that a cell doubly harboring an R factor (R100) and a temperature senditive R factor (Rts1) produces segregant R factors with various resistance patterns, a total of 271 segregant R factors were obtained. There were 163 resistant to (sul, str, kan), 39 resistant to (sul, str, cml, kan), 62 resistant to (sul, str, tet, kan) and finally 7 resistant to (tet, kan). More than 90% of the former 3 segregants were fi⁺ and the remainder, including all of the (tet, kan) segregants, were fi^-. Some fi^- segregants with the former 3 resistance patterns and all of the (tet, kan) segregants were nontransmissible. All of these segregants were still temperature sensitive. Based upon the results of three experiments; (a) the growth at 43C to observe linked loss of the kan gene and the genes derived from R100, (b) a conjugal analysis of the relevant resistant markers, and (c) a transduteional analysis of these same markers, several conclusions were made. The 2R factors both consisting of a circle were supposed to have recombined to form a larger circle which then further resulted in the final formation of smaller circles. The possible bearing of these observations and conelusions on the genetic structure of R100 was discussed.