Transduction of Escherichia coli W3110(R702) and J53(RP4) (10,000 to 100,000 CFU/g of soil) by lysates of temperature-sensitive specialized transducing derivatives of bacteriophage P1 (10,000 to 100,000 PFU/g of soil) (P1 Cm cts, containing the resistance gene for chloramphenicol, or P1 Cm cts::Tn501, containing the resistance genes for chloramphenicol and mercury (Hg) occurred in soil amended with montmorillonite or kaolinite. In nonsterile soil, survival of introduced E. coli and the numbers of E. coli transductants resistant to chloramphenicol or Hg were independent of the clay amendment. The numbers of added E. coli increased more when bacteria were added in Luria broth amended with Ca and Mg(LCB) than when they were added in saline, however the same proportion of E. coli was transduced with both types of inoculum. In sterile soil, total and transduced E. coli and P1 increased by 3 to 4 logs, which was followed by a plateau when they were inoculated in LCB and a gradual decrease when they were inoculated in saline. Transduction appeared to occur primarily in the first few days after addition of P1 to soil. The transfer of Hg or chloramphenicol resistance from lysogenic to nonlysogenic E. coli by phage P1 occurred in both sterile and nonsterile soils. The transductants appeared to be the E. coli that was added. The survival of P1, E. coli hosts, and transductants for at least 28 days in nonsterile soil indicated the potential for genetic transfer via transduction in soil. (Copyright (c) 1988, American Society for Microbiology.)