Use of green fluorescent protein and luciferase biomarkers to monitor survival and activity of Arthrobacter chlorophenolicus A6 cells during degradation of 4-chlorophenol in soil

The recently isolated novel species Arthrobacter chlorophenolicus A6 is cap able of growth on and degradation of high concentrations of 4-chlorophenol (up to 350 mug ml(-1)) as the sole carbon and energy source, This strain sh ows promise for bioremediation of environmental sites contaminated with hig h levels of chlorophenols. In this study, green fluorescent protein (gfp) o r luciferase (luc) genes were used as biomarkers for monitoring cell number and activity, respectively, during degradation of 4-chlorophenol by A. chl orophenolicus cells. The individual marked strains, Arthrobacter chlorophen olicus A6L (luc-tagged) and Arthrobacter chlorophenolicus A6G (gfp-tagged), were monitored during degradation of 250 mug ml(-1) 4-chlorophenol in pure culture and 175 mug g(-1) 4-chlorophenol in soil microcosms. Both gene-tag ged strains were capable of cleaning up the contaminated soil during 9 d in cubation. During the bioremediation experiments, the luc-tagged cells were monitored using luminometry and the gfp tagged cells using flow cytometry, in addition to selective plate counting for both strains. The cells remaine d at high population levels in the soil (evidenced by GFP-fluorescent cell counts) and the A. chlorophenolicus A6L population was metabolically active (evidenced by luciferase activity measurements). These results demonstrate that the Arthrobacter chlorophenolicus A6 inoculum is effective for cleani ng-up soil containing high concentrations of 4-chlorophenol.