need help,,,micro question

BACKGROUND INFORMATION
Kesterson National Wildlife Refuge, California. In the San Joaquin Valley, irrigation water wasn't draining properly, and crops were dying in the water-logged soil. In 1981, a drainage system was built that would channel irrigation runoff into shallow ponds called Kesterson Reservoir. In addition to receiving field runoff, the new reservoir was to be a waterfowl habitat. In 1983, an unusually large number of dead birds was found, indicating that something was wrong with the water.
Selenium from the soil (in the form of selenate, SeO42-) was dissolving in the irrigation water and being carried to Kesterson Reservoir, where it stayed. The concentration of selenium in Kesterson rose to 29 times higher than that which was considered safe.
For now, to prevent the killing of more birds, Kesterson Reservoir is being filled with soil. But the selenium remains.
A number of bacteria, including Bacillus, Acinetobacter, and Pseudomonas, can convert selenate (SeO42-) to nontoxic elemental selenium. The bacteria do this for their own survival-to prevent the accumulation of toxic levels in their cells.

I have to show the chemical reaction for this, I have no idea what I am doing. Can someone point me in the right direction?