Effects of Chromium(VI) and Chromium(III) on Desulfovibrio vulgaris Cells
Desulfovibrio vulgaris ATCC 29579 is a well studied sulfate reducer that has known capabilities of reducing heavy metals and radionuclides, like chromium and uranium. Cultures grown in a defined medium (i.e. LS4D) had a lag period of approximately 40 h when exposed to 50 μMof Cr(VI). Substrate analysis revealed that although chromium is reduced within the first 5 h, growth does not resume for another 35 h. During this time, small amounts of lactate are still utilized but the reduction of sulfate does not occur. Sulfate reduction occurs concurrently with the accumulation of acetate approximately 40 h after inoculation, when growth resumes. Similar amounts of hydrogen are produced during this time compared to hydrogen production by cells not exposed to Cr(VI); therefore an accumulation of hydrogen cannot account for the utilization of lactate. There is a significant decrease in the carbohydrate to protein ratio at approximately 25 h, and this result indicated that lactate is not converted to glycogen. Most probable number analysis indicated that cell viability decreased steadily after inoculation and reached approximately 6 x 104 cells/ml 20 h post-chromium exposure. Regeneration of reducing conditions during chromium exposure does not induce growth and in fact may make the growth conditions even more unfavorable. This result suggested that an increase in Eh was not solely responsible for the decline in viability. Cell pellets collected 10 h after chromium-exposure were unable to resume growth when suspended into fresh medium. Supernatants from these pellets were able to support cell growth upon re- inoculation. D. vulgaris cells treated with a non-dose dependent addition of ascorbate at the same time of Cr(VI) addition did not enter a lag period. Ascorbate added 3 h post-Cr(VI) exposure did not prevent the growth lag. These results indicated that Desulfovibrio utilized lactate to reduce Cr(VI) without the reduction of sulfate, that the decline in cell viability and cell growth was most likely a consequence of Cr(III), and that an organic ligand could protect D. vulgaris cells from Cr(III) toxicity. Lactate consumption decoupled from sulfate reduction in the presence of Cr(VI) could provide organic carbon for organo- Cr(III) complexes.
- Research Organization:
- Miami University, Oxford, OH
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 925435
- Report Number(s):
- CONF-ERSP2007/1023312a; R&D Project: ERSD 1023312a; TRN: US200807%%355
- Resource Relation:
- Conference: Annual Environment Remediation Science Program (ERSP) Principal Investigator Meeting, April 16-19, 2007, Lansdowne, VA
- Country of Publication:
- United States
- Language:
- English
Similar Records
Integrated Ecogenomics Study for Bioremediation of Cr(VI) at Hanford 100H Area
Cr(VI) reduction and physiological toxicity are impacted by resource ratio in Desulfovibrio vulgaris