Molybdenum can exist in multiple oxidation states (III to VI), but is most frequently found as Mo(VI) in
molybdate (MoO42-). Molybdenum is an essential trace element and is found in
microbial enzymes more frequently than the other group V elements. Enzyme-bound molybdenum has been
demonstrated to exist in only two forms, both of them as distinct
cofactors that can be removed from their respective enzymes.
One form is the MoFe cofactor of nitrogenase; the other is
cofactor of other molybdenum-containing enzymes (reviewed by Kisker et al, 1997).
The regulation of molybdate transport has been studied, and molybdenum import is known
to occur via inducible ABC-type transporters, with transport also occurring through sulfate uptake systems and nonspecific
anion transporters (reviewed by Self et al, 2001). A variety of bacteria and archaea can reduce molybdenum(VI) to molybdenum(V) under
aerobic and anaerobic conditions (reviewed by Lovley, 1993) . The mechanisms of prokaryotic molybdenum reduction are not known.
For more information:
Medline for molybdenum metabolism AND bacteria
Database of Molybdenum in Human Health and the Environment