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Appl. Environ. Microbiol., 05 1995, 1691-1698, Vol 61, No. 5
EM Top, WE Holben and LJ Forney
The diversity of 2,4-dichlorophenoxyacetic acid (2,4-D)-degradative
plasmids in the microbial community of an agricultural soil was examined by
complementation. This technique involved mixing a suitable Alcaligenes
eutrophus (Rifr) recipient strain with the indigenous microbial populations
extracted from soil. After incubation of this mixture, Rifr recipient
strains which grow with 2,4-D as the only C source were selected. Two A.
eutrophus strains were used as recipients: JMP228 (2,4-D-), which was
previously derived from A. eutrophus JMP134 by curing of the
2,4-D-degradative plasmid pJP4, and JMP228 carrying pBH501aE (a plasmid
derived from pJP4 by deletion of a large part of the tfdA gene which
encodes the first step in the mineralization of 2,4- D). By using
agricultural soil that had been treated with 2,4-D for several years,
transconjugants were obtained with both recipients. However, when untreated
control soil was used, no transconjugants were isolated. The various
transconjugants had plasmids with seven different EcoRI restriction
patterns. The corresponding plasmids are designated pEMT1 to pEMT7. Unlike
pJP4, pEMT1 appeared not to be an IncP1 plasmid, but all the others (pEMT2
to pEMT7) belong to the IncP1 group. Hybridization with individual probes
for the tfdA to tfdF genes of pJP4 demonstrated that all plasmids showed
high degrees of homology to the tfdA gene. Only pEMT1 showed a high degree
of homology to tfdB, tfdC, tfdD, tfdE, and tfdF, while the others showed
only moderate degrees of homology to tfdB and low degrees of homology to
tfdC.(ABSTRACT TRUNCATED AT 250 WORDS)
Copyright © 1995, American Society for Microbiology
Characterization of diverse 2,4-dichlorophenoxyacetic acid-degradative plasmids isolated from soil by complementation
National Science Foundation Center for Microbial Ecology, Michigan State University, East Lansing 48824, USA.
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