Degradation of chlorobenzenes at nanomolar concentrations by Burkholderia sp. strain PS14 in liquid cultures and in soil

Abstract

The utilization of 1,2,4,5-tetrachloro-, 1,2,4-trichloro-, the three isomeric dichlorobenzenes and fructose as the sole carbon and energy sources at nanomolar concentrations was studied in batch experiments with Burkholderia sp. strain PS14. In liquid culture, all chlorobenzenes were metabolized within 1 h from their initial concentration of 500 nM to below their detection limits of 0.5 nM for 1,2,4,5-tetrachloro- and 1,2,4-trichlorobenzene and 7.5 nM for the three dichlorobenzene isomers, with 63% mineralization of the tetra- and trichloroisomers. Fructose at the same initial concentration was, in contrast, metabolized over a 4-h incubation period down to a residual concentration of approximately 125 nM with 38% mineralization during this time. In soil microcosms, Burkholderia sp. strain PS14 metabolized tetrachlorobenzene present at 64.8 ppb and trichlorobenzene present at 54.4 ppb over a 72-h incubation period to below the detection limits of 0.108 and 0.09 ppb, respectively, with approximately 80% mineralization. A high sorptive capacity of Burkholderia sp. strain PS14 for 1,2,4, 5-tetrachlorobenzene was found at very low cell density. The results demonstrate that Burkholderia sp. strain PS14 exhibits a very high affinity for chlorobenzenes at nanomolar concentrations.

FIG. 1

Metabolism and mineralization of 1,2,4,5-TeCB, 1,2,4-TCB, and fructose in liquid cultures of Burkholderia sp. strain PS14 in mineral salts medium. Percentages of mineralization (solid symbols) and nanomolar concentrations (open symbols) of 1,2,4,5-TeCB, 1,2,4-TCB, and fructose are shown. (A) ■, [¹⁴C]1,2,4,5-TeCB; ●, [¹⁴C]1,2,4-TCB; □, 1,2,4,5-TeCB; ○, 1,2,4-TCB; ▵, 1,2,4-TCB in the sterile control. (B) ●, [¹⁴C]fructose; □, fructose. The values are the means of results of two to four independent experiments, and error bars show standard deviations.

FIG. 2

Metabolism and mineralization of 1,2,4,5-TeCB in unsterilized and sterilized BBA standard soil inoculated with Burkholderia sp. strain PS14. Percentages of mineralization of [¹⁴C]1,2,4,5-TeCB (solid symbols) and concentrations (in parts per billion) of 1,2,4,5-TeCB (open symbols) in nonsterile (circles) and sterile (squares) soil are shown. ⋄, concentrations (in parts per billion) of 1,2,4,5-TeCB in the uninoculated control; ▵, CFU of Burkholderia sp. strain PS14 per gram (wet weight) of sterile soil. The values are the means of results of two to four independent experiments, and error bars show standard deviations.

FIG. 3

Metabolism and mineralization of 1,2,4-TCB in sterilized BBA standard soil inoculated with Burkholderia sp. strain PS14. Percentages of mineralization of [¹⁴C]1,2,4-TCB (■) and concentrations of 1,2,4-TCB (in parts per billion) (□) in soil are shown. ○, concentration (in parts per billion) of 1,2,4-TCB in the uninoculated control; ▵, CFU per gram (wet weight) of soil. The values are the means of results of four independent experiments, and the error bars show standard deviations.

FIG. 4

Linear isotherm for 1,2,4,5-TeCB sorption to Burkholderia sp. strain PS14. The values represent the means of duplicate samples.