Transfer-defective mutants of sex factors in Escherichia coli. I. Defective mutants and complementation analysis.

HE fertility factor, F, controls conjugal fertility of Escherichia coli Kl2 ( LEDERBERG, CAVALLI and LEDERBERG 1952; HAYES 1953). F also determines functions such as immunity to superinfection by a second F factor (MAAS 1963) ; growth inhibition of certain phages such as tau ( 7 ) (HAKURA, OTSUJI and HIROTA 1964) , T7 ( MAKEL;~, MAKEL;~ and SOIKKELI 1964), and T3 ( SCHELL et al. 1963) ; and formation of F-pili (BRINTON, GEMSKI and CARNAHAN 1964). F-pili are used in conjugation, correspond to the f f antigen ( ~ R S K O V and ~ R S K O V 1960; ISHIBASHI 1967), and are the receptors for a group of male-specific phages. These characters controlled by the F factor were collectively called “F properties” by HIROTA et al. (1964). Other genetic elements such as the resistance factor (R) , responsible for multiple drug resistance (OCHIAI et al. 1959; AKIBA et al. 1960), and the colicin factor (Col) , determining the production of bactericidal substances (GRATIA 1932; FRBDBRICQ 1957), also have been shown to have many properties similar to those of the F factor. Both factors are conjugally transmissible and confer donor ability on the host bacteria (OZEKI and HOWARTH 1961; SUGINO and HIROTA 1962). Strains carrying some R or Col factors produce pili similar to F-pili (reviewed by MEYNELL, MEYNELL and DATTA 1968). Thus F and these elements have similar genetic determinants concerning conjugal activity and may be collectively called sex factors. Defective mutants lacking mating capacity have been obtained from cells harboring the F factor (LEDERBERG and LEDERBERG 1956; RIGHTER 1961; CUZIN 1962) and the R factor (SUGINO and HIROTA 1962; HIROTA, FUJII and NISHIMURA 1966). Some cooperation in conjugal activity is shown by these factors. Conjugal fertility of nontransmissible R mutants is restored by introduction of an F factor (HIROTA, FUJII and NISHIMURA 1966). Introduction into the female-3 mutant (RICHTER 1961), sfa strains (ADELBERG and BURNS 1960), or into “F-refractory” mutants (LEDERBERG and LEDERBERG 1956), of an R or F factor restores the fertility with an orientation of chromosome transfer characteristic of the original Hfr strains (SUGINO and HIROTA 1962; HIROTA, FUJII and NISHIMURA 1966). Analogous observations also have been reported between Col and F factors (OZEKI, STOCKER and SMITH 1962; CLOWES 1963).