A DEMONSTRATION OF BACTERIAL CONJUGATION WITHIN THE ALIMENTARY CANAL OF RHABDITIS NEMATODES

Rhabditis nematodes fed a diet of Escherichia coli defecate viable und igested bacteria. These bacteria retain phenotypic characteristics, in cluding those encoded on plasmids. Nematodes can survive a 2-min surfa ce sterilization with 2% chlorine bleach: internalized bacteria also s un;ive this treatment and are released in the nematode wastes, Bacteri a alone or on the surface of dead nematodes are unable to survive incu bation with this solution. There were 3.2 x 10(5) viable bacteria per nematode, indicating that sufficient bacteria were present for gene tr ansfer. Transconjugants (lac(-) nal(R) str(R) cm(R)) were recovered in the nematode fecal material following a protocol where nematodes were initially fed a plasmidless lac(-) nal(R) str(S) cm(S) E. coli and th en, after surface sterilization, a lac(+) nal(S) E. coli plasmid donor containing the conjugative R100JA (str(R) cm(R)) plasmid. The presenc e of plasmids in the transconjugants was confirmed by gel electrophore sis. The occurrence of conjugation in the gut was confirmed by dissect ion of individual surface-sterilized nematodes and isolation of transc onjugants.