Aerobic chromate reduction by Bacillus subtilis.
We have studied the reduction of hexavalent chromium (chromate) to the less toxic trivalent form by using cell suspensions and cell-free extracts from the common soil bacterium, Bacillus subtilis. B. subtilis was able to grow and reduce chromate at concentrations ranging from 0.1 to 1 mM K2CrO4. Chromate reduction was not affected by a 20-fold excess of nitrate-compound that serves as alternate electron acceptor and antagonizes chromate reduction by anaerobic bacteria. Metabolic poisons including sodium azide and sodium cyanide inhibited chromate reduction. Reduction was effected by a constitutive system associated with the soluble protein fraction and not with the membrane fraction. The reducing activity was heat labile and showed a Km of 188 microns CrO4(2)-. The reductase can mediate the transfer of electrons from NAD(P)H to chromate. The results suggest that chromate is reduced via a detoxification system rather than dissimilatory electron transport.
Garbisu
C
C
Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias, Universidad del País Vasco, Bilbao, Spain.
Alkorta
I
I
Llama
M J
MJ
Serra
J L
JL
D000332:Aerobiosis; D001412:Bacillus subtilis / Q000254:growth & development / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism; D002840:Chromates / Q000378:metabolism*; D007700:Kinetics; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction
D001426:Bacterial Proteins; D002840:Chromates; D009249:NADP