In soil, conjugative transposition was observed at pH values near neutrality. This is similar to observations using E. coli soil matings and conjugal plasmids. With Tn 916 matings, conjugal activity drops off completely as pH becomes more acidic or alkaline. This may be due to a weakening of the physiological state of the cells or a destabilization of the mating pairs. Finally, for Tn 916 to be transferred in a natural population, it would need to be introduced into the soil microflora by a host organism such as E. faecalis .
Tetracycline resistance is common in isolates of E. faecalis from animal waste.
Although a wide range of each environmental factor was examined here, it is important to note that conjugation was detected over the range for each parameter that would be considered normal conditions in a natural environment. Tn 916 transfer was observed at frequencies very similar to those in sterile systems. The results presented here indicate the ability of Tn 916 to enter the bacterial population of the soil and, once there, move between soil bacteria in this population over a wide range of environmental conditions. Because Tn 916 can mobilize nonconjugal DNA, it would not only transfer tetracycline resistance but could transfer many other genes as well. This type of activity could allow mobilization of DNA from genetically engineered microorganisms into the indigenous soil population.