Gene probe analysis of soil microbial populations selected by amendment with 2,4-dichlorophenoxyacetic acid.
Soils with a history of 2,4-dichlorophenoxyacetic acid (2,4-D) treatment at field application rates and control soils with no prior exposure to 2,4-D were amended with 2,4-D in the laboratory. Before and during these treatments, the populations of 2,4-D-degrading bacteria were monitored by most-probable-number (MPN) enumeration and hybridization analyses, using probes for the tfd genes of plasmid pJP4, which encode enzymes for 2,4-D degradation. Data obtained by these alternate methods were compared. Several months after the most recent field application of 2,4-D (approximately 1 ppm), soils with a 42-year history of 2,4-D treatment did not have significantly higher numbers of 2,4-D-degrading organisms than did control soils with no prior history of treatment. In response to laboratory amendments with 2,4-D, both the previously treated soils and those with no prior history of exposure exhibited a dramatic increase in the number of 2,4-D-metabolizing organisms. The MPN data indicate a 4- to 5-log population increase after one amendment with 250 ppm of 2,4-D and ultimately a 6- to 7-log increase after four additional amendments, each with 400 ppm of 2,4-D. Similarly, when total bacterial DNA from the soil microbial community of these samples was analyzed by using a probe for the tfdA gene (2,4-D monoxygenase) or the tfdB gene (2,4-dichlorophenol hydroxylase) a dramatic increase in the level of hybridization was observed in both soils.(ABSTRACT TRUNCATED AT 250 WORDS)
Holben
W E
WE
Center for Microbial Ecology, Michigan State University, East Lansing 48824.
Schroeter
B M
BM
Calabrese
V G
VG
Olsen
R H
RH
Kukor
J K
JK
Biederbeck
V O
VO
Smith
A E
AE
Tiedje
J M
JM
D015084:2,4-Dichlorophenoxyacetic Acid / Q000378:metabolism*; D001419:Bacteria / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D001483:Base Sequence; D001673:Biodegradation, Environmental; D015342:DNA Probes; D004269:DNA, Bacterial / Q000235:genetics; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D012988:Soil Microbiology
D015342:DNA Probes; D004269:DNA, Bacterial; D015084:2,4-Dichlorophenoxyacetic Acid