Transduction of Escherichia coli in soil

Bacteriophage P1-mediated generalized transduction of Escherichia coli K-12 was assessed in nonsterile soil. Auxotrophic recipient cells (thr- leu- thi- rpsL) were incubated in a sandy and a silty clay loam soil, and the transducing phage lysates from prototrophic strains carrying transposon 10(Tn10) in either purE or aroL regions were added. At intervals, the bacterial populations derived from the soils were plated on selective-differential media to enumerate prototrophic (thr+, leu+, or Tcr) transductants. Of 100 bacterial isolates obtained on the selective-differential media, 58 (14 thr+; 11, leu+; 33 Tcr) were confirmed E. coli transductants. The frequency of transduction in soil was ca. 10(-6). These data demonstrate the potential use of bacteriophage P1 to genetically manipulate E. coli in situ.