Evidence for plasmid-mediated restriction-modification in XXXX intracellulare.

@entity7666 @entity3069 @entity11381
@entity3069 intracellulare strain LR25 carries three plasmids with molecular weights of 11.2, 18.3 and 107 X 10(6) as determined by electron microscopy. A number of phages propagated on @entity7666 ATCC 607 were tested for their ability to infect strain LR25. Phage JF2 gave an efficiency of plating of 10(-4) on strain LR25, but phage JF2 propagated on strain LR25 infected strain LR25 and @entity7666 with equal high efficiency. This indicated the presence of a restriction-modification (R-M) system in strain LR25 that was not present in @entity7666 LR25 was grown in the presence of @entity11381 to eliminate the plasmids and tested for sensitivity to phage JF2. One of forty colonies was found to be R-M-deficient. This strain, designated strain LR163, lacks the three plasmids present in strain LR25. The results indicate that the R-M system is plasmid-coded. Strain LR163 was sensitive to several phages to which strain LR25 was resistant and for which we were unable to isolate modified phage. This suggests that some plasmid-coded function in addition to restriction is involved. An R-M system was also demonstrated in @entity3069 intracellulare strain LR131 using phage JF1. This strain does not carry plasmids.
