Biodegradation of Atrazine byAgrobacterium radiobacterJ14a and Use of This Strain in Bioremediation of Contaminated Soil

Abstract

We examined the ability of a soil bacterium, Agrobacterium radiobacter J14a, to degrade the herbicide atrazine under a variety of cultural conditions, and we used this bacterium to increase the biodegradation of atrazine in soils from agricultural chemical distribution sites. J14a cells grown in nitrogen-free medium with citrate and sucrose as carbon sources mineralized 94% of 50 μg of [14C-U-ring]atrazine ml−1 in 72 h with a concurrent increase in the population size from 7.9 × 105 to 5.0 × 107 cells ml−1. Under these conditions cells mineralized the [ethyl-14C]atrazine and incorporated approximately 30% of the 14C into the J14a biomass. Cells grown in medium without additional carbon and nitrogen sources degraded atrazine, but the cell numbers did not increase. Metabolites produced by J14a during atrazine degradation include hydroxyatrazine, deethylatrazine, and deethyl-hydroxyatrazine. The addition of 105 J14a cells g−1 into soil with a low indigenous population of atrazine degraders treated with 50 and 200 μg of atrazine g−1soil resulted in two to five times higher mineralization than in the noninoculated soil. Sucrose addition did not result in significantly faster mineralization rates or shorten degradation lag times. However, J14a introduction (105 cells g−1) into another soil with a larger indigenous atrazine-mineralizing population reduced the atrazine degradation lag times below those in noninoculated treatments but did not generally increase total atrazine mineralization.

Screen and Study of Tetracycline‐Degrading Bacteria From Activated Sludge and Granular Sludge

“…The significant improvement in degradation rate after adding yeast extract may be attributed to the presence of microorganisms that produce certain enzymes beneficial to the degradation of tetracycline. [34] Therefore, yeast extract was used as an extra nitrogen source for further study.…”

Evaluation of microbial inoculation and vegetation to enhance the dissipation of atrazine and metolachlor in soil

“…The two herbicide-degrading bacteria used in the studies included A. radiobacter strain J14a, which degrades ATR [6], and Pseudomonas fluorescens strain UA5-40, which degrades alachlor [26] and MET [18]. The UA5-40 strain was supplied by R. Zablotowicz, Agricultural Research Service, U.S. Department of Agriculture (Stoneville, MS).…”

“…The UA5-40 strain was supplied by R. Zablotowicz, Agricultural Research Service, U.S. Department of Agriculture (Stoneville, MS). The J14a was grown in a basal minimal salts medium supplemented with vitamins, trace elements, and ATR [6]. The ATR was the sole N source.…”

“…The UA5-40 was grown in a half-strength tryptic soy broth containing 50 mg/L of MET. When the bacteria were grown to late log phase on a rotary shaker, they were centrifuged and resuspended in sterile phosphate buffer [6]. Cell densities were determined by plate count.…”

“…The remediation of ATR-contaminated soils by pure cultures of bacteria has been investigated extensively [4][5][6][7]. The effectiveness of remediation with ATR-degrading bacteria in nonsterile soils has varied.…”