Aerobic Cr(VI) reduction by Thermus scotoductus strain SA-01.
OBJECTIVE
To evaluate Thermus scotoductus SA-01's ability to reduce Cr(VI) aerobically.


RESULTS
T. scotoductus SA-01 is able to reduce Cr(VI) aerobically when grown in a complex organic medium containing Cr(VI) concentrations up to 0.5 mmol l(-1). Suspension of T. scotoductus SA-01 cells also reduced Cr(VI) aerobically under nongrowth conditions using a variety of electron donors as well as in the absence of an exogenous electron donor. The optimum temperature and pH for Cr(VI) reduction under nongrowth conditions were found to be 80 degrees C and 7, respectively. It was also found that the Cr(VI) reduction was catalysed by a cytoplasmic, constitutively expressed enzyme.


CONCLUSIONS
Apart from SA-01's ability to reduce Cr(VI) through a strictly anaerobic membrane-bound mechanism (unpublished data), it also has a second enzyme localized in the cytoplasm that can reduce Cr(VI) aerobically. As this enzyme is constitutively expressed and not induced by Cr(VI), it remains to be determined whether it has any other physiological functions.


CONCLUSIONS
This is the first report of a Thermus species able to reduce Cr(VI) aerobically and extends the knowledge of parameters associated with Cr(VI) reduction. Employing thermophiles in bioremediation using industrial bioreactors would cancel the need for expensive cooling systems.
Opperman
D J
DJ
Department of Microbial, Biochemical and Food Biotechnology, University of the Free State, Bloemfontein, South Africa.
van Heerden
E
E
D000332:Aerobiosis; D001431:Bacteriological Techniques; D001673:Biodegradation, Environmental; D002857:Chromium / Q000737:chemistry*; D003593:Cytoplasm / Q000201:enzymology; D006256:Hazardous Waste; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D013824:Thermus / Q000201:enzymology / Q000502:physiology*; D014871:Water Microbiology; D014874:Water Pollutants, Chemical / Q000737:chemistry*
D006256:Hazardous Waste; D014874:Water Pollutants, Chemical; D002857:Chromium