TABLE 1.

Methylation of Hg_I spike by D. propionicus with and without added sulfide^a

Culture	Concn (ng liter−1)		Turnover	Fraction of spike methylated
	Unfiltered MeHg	Filtered HgI
Ambient A	67.8	76.9	0.88	0.034
Ambient B	71.9	67.6	1.06	0.036
Avg ± SE			0.97 ± 0.09	0.035 ± 0.001
Sulfide + A	10.0	13.3	0.75	0.005
Sulfide + B	11.2	20.0	0.56	0.006
Avg ± SE			0.65 ± 0.10	0.005 ± 0.0003

^aSulfide concentrations were 0.55 mM in ambient cultures and 1.4 mM in sulfide+ cultures; spike concentration was 2,000 ng Hg liter⁻¹. Turnover = [unfiltered MeHg]/[filtered Hg_I]; fraction methylated = [unfiltered MeHg]/[spike Hg_I].