THE PRODUCTION OF S-34-DEPLETED SULFIDE DURING BACTERIAL DISPROPORTIONATION OF ELEMENTAL SULFUR

Bacteria that disproportionate elemental sulfur fractionate sulfur iso topes such that sulfate is enriched in sulfur-34 by 12.6 to 15.3 per m il and sulfide is depleted in sulfur-34 by 7.3 to 8.6 per mil. Through a repeated cycle of sulfide oxidation to S-0 and subsequent dispropor tionation, these bacteria can deplete sedimentary sulfides in sulfur-3 4. A prediction, borne out by observation, is that more extensive sulf ide oxidation will lead to sulfides that are more depleted in sulfur-3 4. Thus, the oxidative part of the sulfur cycle creates circumstances by which sulfides become more depleted in sulfur-34 than would be poss ible with sulfate-reducing bacteria alone.