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

ZABALOY, MARÍA CELINA; GÓMEZ, MARISA ANAHÍ

Buenos Aires

Congreso; Biolatina 2006. VII Feria Congreso Latinoamericano de Biotecnología. III Congreso Argentino de Biotecnología; 2006

Foro Argentino de Biotecnología (FAB)

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-D, succinate (S), 2,4-D+S and untreated control (C). 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 sub-cultured in liquid medium to confirm 2,4-D degradation. MPN2,4-D was relatively high (4.6 x102 bacteria/g) on day 0, indicating that this soil has a stable and measurable degrader population. There were significant differences in 2,4-D degrader abundances (p0.38) or sampling time (p>0.98). Selected 2,4-D- degrading isolates obtained via enrichment culture were further subjected to genotypic and phenotypic analysis. Implications of the results on bioremediation strategies are discussed.