To examine the ability of Tn916 to conjugally transfer in the soil environment, matings were performed in a laboratory soil microcosm. In sterile soil, Tn916 was observed to transfer from Bacillus subtilis to Bacillus thuringiensis subsp. israelesis at an average frequency of 2.1 x10-5. Moreover, transfer occurred from Enterococcus faecalis to B. thuringiensis at an average frequency of 2.3 x10-6. Performing the above experiments in nonsterile soil had minimal effects on the transfer frequencies. The conjugal transfer of Tn916 between Bacillus species was evaluated over varying conditions of soil moisture, temperature, pH and available nutrients. Optimal transfer occurred at 2-5% moisture even though transfer was observed over the entire range tested. Detectable transfer only occurred between 18∘ and 37∘C (optimum at 30∘C) and in a range of pH of 6-8.9. Increasing the nutrient level in the soil enhanced transfer frequencies. Additionally, Tn916 mobilization of the nonconjugative plasmid pC194 occurred at an average frequency of 2.0 x10-6. Because Tn916 was originally isolated from E. faecalis, swine lot effluent was examined for the presence of Tn916-like elements. Outflow samples from the Iowa State University swine farrowing house were used to isolate E. faecalis. Of the enterococci isolated, 71% were resistant to tetracycline. To screen these isolates for conjugal activity, a microassay was developed. Among the tetracycline-resistant enterococci isolated from the outflow sample, 34% were able to transfer tetracycline resistance to a B. thuringiensis recipient. The transfer frequencies for 10 random isolates were determined to be near those for transfer of Tn916 from E. faecalis to B. thuringiensis on filters, as well as in a soil environment. Furthermore, these elements were shown to be able to mobilize plasmid DNA between Bacillus species. Southern blot and PCR analysis showed these elements to share extensive structural homology with Tn916 and are hence referred to as Tn916-like elements. Because it was determined that these elements are functional in the soil environment, when introduced in effluent, they could facilitate the dissemination of antibiotic resistance genes as well as other nonconjugal DNA in the soil.