[Study on infection of different strains of Vibro cholerae O1 by El Tor CTXPhi]

To study the horizontal transfer efficiencies of filamentous bacteriophage CTXPhi in different V. cholera O1 strains and the phage immunities of these strains. The infectious El Tor CTXPhi particles genetic marked by chloramphenicol resistance gene were used to infect four different V. cholerae O1 strains in vivo and in vitro. Selected the infected clones based on its character of chloramphenicol resistance and identified and judged the exist form of CTXPhi genome through Southern bolt and other hybridization methods. Calculated the infection rates of different strains and compared each other. Then we analyzed the mechanism of infection and phage immunity. The infection rate of classic strain 1119 with the genetic marked CTX(ET)Phi in vivo is much higher than that in vitro. In vitro experiment, the rate of 1119 is higher than other three El Tor strains. And in El Tor strains, the infection frequency of IEM101 that had no rstR gene is 100 to 1000 times higher than other two strains containing rstR. Classical biotype strain is more susceptible to CTX(ET)Phi particles than El Tor strains. Expression of TCP and the phage immunity mediated by rstR gene affect the horizontal transfection of CTXPhi in V. cholerae strains.