Adult sheep were given into the rumen 10 cells each of donor strains of containing an R factor and prospective salmonella-recipient organisms and were maintained on a diet of lucerne chaff; the animals excreted the organisms, remained healthy, and no transfer of the R factor was detected. When the animals were starved for 48 h before inoculation, the ruminai environment was altered so that, on resumption of feeding, small numbers 10-10 cells-less than one cell per ml of rumen fluid) of the introduced organisms were able to multiply and reach sufficient numbers for the transfer of R factors to occur within the rumen. One animal, given 7·8 × 10 cells of recipient after starvation for 48 h, became a carrier of this organism. A second animal, given 4·4 × lO cells of after starvation for 48 h, developed acute, fatal salmonellosis 5 days later; at the time of death, large numbers of salmonella organisms 10 cells per g) were present in the faeces; these included many 10 cells per g) that had received the R factor by transfer These results indicate that short periods of starvation may enhance the transfer of R factors and possibly other plasmids between suitable micro-organisms , and may increase the susceptibility of animals to pathogenic micro-organisms.


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