Detection and isolation of bacteria degrading the chloroaromatic herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) from an agricultural soil.

ZABALOY, C.; GÓMEZ, M.

Buenos Aires

Congreso; BIOLATINA 2006. VII Feria Congreso Latinoamericano de Biotecnología. III Congres Argentino de Biotecnología.; 2006

DETECTION ANO ISOLATION OF BACTERIA DEGRADING THE CHLOROAROMATIC HERBICIDE 2,4-DICHLOROPHENOXY ACETIC ACID (2,4-D) FROM AN AGRICULTURAL SOIL Zabaloy, M.C,  Gómez, M.A. Departamento de Agronomía, Universidad Nacional del Sur, San Andrés 800, Bahía Blanca (8000), Argentina. The aim of the present study was to enumerate and isolate soil bacteria with the ability to degrade 2,4-dichlorphenoxyacetic acid (2,4-D), Furthermore, the influence of the natural substrate succinate on the population of 2,4-D-degrading bacteria was assessed. Soil microcosms were treated with 2,4-0, succinate (S), 2,4-D+S and untreated control (e). Microcosms were sampled 4 and 33 days after treatment, and the presence of 2,4-D degraders was assessed by most-probable-number (MPN) method, using indicator medium. Presumptive positive tubes were confirmed by UV spectra. Aerobic heterotrophic bacteria population (AHB) was estimated in 10 % NA. Enrichment cultures were prepared from the highest dilution positive tubes and were streaked on 2,4-D solid medium. Well-separated colonies were subcultured in liquid medium to confírm 2,4-D degradation. MPN 2,4-D was relatively high (4.6´ 102 bacteria/g) on day 0, indicating that this soil has a stable and measurable degrader population. There were significant differences in 2,4-0 degrader abundances (p<0.05) between theuntreated (4.6´ 102 bacteria/g) and 2,4-D-treated microcosms (1.2-1. 9´ 104 bacteria/g) 4 days after treatment. The addition of S to 2,4-D-treated microcosms (2,4-D+S) seemed to increase degrader population (although not statistically significant). An increase of 1-order- of -magnitude in MPN2,4-D in both 2,4-D-treated microcosms was observed 33 days after treatment. The density of AHB (1.26´ 107 CFU/g) was not affected by the treatments (p>0.38) or sampling time (p>0.98). Selected 2,4-D- degrading isolates obtained via enrichment culture were further subjected to genotypic and phenotypíc analysis. Implications of the results on bioremediation strategies are discussed