Transmission electron microscopy analysis of a novel organo-Cr(III) degrading bacterium
EMSL Project ID
8892
Abstract
Microbial reduction of soluble hexavalent chromium [Cr(VI)] is thought to result in the production of an insoluble trivalent [Cr(III)] precipitate. Bioremediation methods based on this idea have been investigated as a method for clean up of Cr(VI) contaminated environments. However, recent evidence demonstrates that soluble organo-Cr(III) complexes are readily formed upon microbial, enzymatic, and chemical reduction of Cr(VI), instead of insoluble Cr(OH)3 precipitates. The presence of soluble Cr(III) species has been detected in the environment, but their fate and recalcitrance remains unknown. In our study, a bacterium, PTX1 capable of mineralizing an enzymatically produced organo-Cr(III) complex, NAD+-Cr(III), was isolated and characterized. The bacterium utilized both free NAD+ and NAD+ in the NAD+-Cr(III) complex as a carbon and energy source. Bacterial mineralization of the NAD+-Cr(III) appears to result in the precipitation of Cr(III) on the bacterial surface as detected by transmission electron microscopy (TEM). Analysis of the bacterium by the TEM/EDS at EMSL would provide improved images of the microbes and further clarify Cr(III) as being a significant component of the cell surface precipitate. This would confirm help confirm our hypothesis of microbial utilization of soluble organo-Cr(III) end-products resulting in a final insoluble Cr(III) precipitate.
Project Details
Project type
Exploratory Research
Start Date
2004-05-01
End Date
2006-05-10
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Hansen, R. F., Engelhard, M., and Raff, J., ?Toward an Improved Understanding of the Role of Soil Organic Matter in NOy Cycling through Investigation of Heterogeneous Reactions with NO2+.? Poster presentation (B13G-1827) at American Geophysical Union Fall Meeting 2017, New Orleans, LA, Dec. 11, 2017.
Hansen R.F., R.B. Abney, M.H. Engelhard, D.P. Veghte, S. China, and J.D. Raff. 12/12/2018. "Investigation of the Mechanism of the Reaction of Soil Organic Matter with N2O5." Presented by R.F. Hansen at AGU Fall 2018, Washington, District Of Columbia. PNNL-SA-140108.
Kebede M A,Bish D L,Lozovyi Y ,Engelhard M H,Raff J D 2016. "The Role of Iron-Bearing Minerals in NO2 to HONO Conversion on Soil Surfaces" Environmental Science & Technology 50(16):8649–8660. 10.1021/acs.est.6b01915
Puzon GJ, YC Huang, A Dohnalkova, and L Xun. 2008. "Isolation and characterization of an NAD+-degrading bacterium PTX1 and its role in chromium biogeochemical cycle." Biodegradation 19(3):417-424. doi:10.1007/s10532-007-9147-1
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