Monday, November 13, 2006 - 11:15 AM
123-3
The Influence of Antimicrobial Chemicals on Soil and Herbicide Degrading Bacteria.
The antimicrobial chemicals tylosin (Tyl) and chlortetracycline (CTC) are used as growth promoters in animal production and can be excreted as the parent compound. Landspreading manure can move these chemicals into the soil. The objective of this study was to determine if Tyl and CTC changed the growth or atrazine degrading activity of Pseudomonas ADP, the 2,4-D degrading activity of Sphingobium herbicidovorans, or whole soil degrading capacity of atrazine. Pseudomonas ADP was cultured with atrazine as the sole N source for 5 d under control conditions or with 2.5 ppm Tyl or CTC. The activity of S. herbicidovorans was measured over a 14-d period using14C-labeled 2,4-D. Whole soil spiked with 14C labeled atrazine was treated with 2.5 ppm of Tyl or CTC. Atrazine was fully degraded after 24 h in the control and Tyl cultures and after 72 h in the CTC culture. About 88% of the 2,4-D in control treatments was mineralized by the 2,4-D degraders 96 h after treatment, whereas Tyl slowed the initial degradation with only 4% mineralized by 10 days after treatment (DAT). However by 14 DAT, recovery occurred and the amount mineralized in the Tyl treatment was similar to the control. CTC substantially decreased the activity of S. herbicidovorans with only 12% of the added 2,4-D mineralized 14 DAT. CTC decreased the amount of atrazine degraded in whole soil with 12% decrease in atrazine degraded compared to the control whereas, Tyl had no effect.
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