In all treatment conditions the highest amount of sulfide was produced

by Cyanidioschyzon, especially when cells were supplemented with sulfate during metal exposure and even more when also pretreated with extra sulfate (Figure 2B; p < 0.05). Similar trends also occurred but not to the same degree in Chlamydomonas (Figure 2A; p < 0.05). The highest amounts of metal sulfide production were 3.5 (approx. 64 fold increase) and 1.2 μmol per mg protein (approx. 4 fold increase) for Cyanidioschyzon and Chlamydomonas, respectively. ICG-001 concentration The cyanobacterium Synechococcus in the sulfate pretreated cells produced a much lower amount of metal sulfide at 0.48 μmol per mg protein (approx. 3.5 fold increase) and this required 48 h to become significantly different from the control. However, this species was exposed to only 2 μM Cd(II), one fiftieth that of the other species because it is not as tolerant to cadmium. In contrast to the two eukaryotic algal species, the cyanobacterium also made similar amounts of metal sulfides during sulfite treatments. No species made significantly more sulfide as a product of cysteine supplementation after 48 h, although Synechococcus did make significantly more after 24 h. Figure 2 Cadmium induced sulfide formation at 0 (grey), 24 (cross-hatched) and 48 h (black) for Chlamydomonas reinhardtii (A) and Cyanidioschyzon merolae (B) in 100 μM Cd(II), and Synechococcus leopoliensis

(C) in 2 μM Cd(II). Means and SE (n = 4). An asterisk indicates significantly greater than the respective Cd(II) containing control (p < 0.05). Serine acetyltransferase and O-acetylserine(thiol)lyase coupled activity Each species had significantly different initial Gefitinib in vitro SAT/OASTL activities under control conditions (ANOVA, p < 0.05; Figure 3). Exposure to Cd(II) enhanced the activity of coupled SAT and OASTL over controls with no added metal after

48 hrs to 2.0, 1.7, and 3.2 fold in Chlamydomonas (Figure 3A), Cyanidioschyzon (Figure 3B), and Synechococcus (Figure 3C), respectively. This treatment Metformin molecular weight also resulted in the highest enzyme activities in each of the species. The only other Cd(II) treatments that were higher than the controls in all three species were the simultaneously sulfate fed, and the pre- and simultaneously sulfite fed cells. The pre- and simultaneously cysteine-fed Chlamydomonas and Synechococcus had the lowest activities (ANOVA, p < 0.05), although this was not the case for Cyanidioschyzon. In the latter species the treatments with the lowest activities did not differ from the control, and the pre- and simultaneously cysteine-fed cells were significantly different from the control (ANOVA, p < 0.05). Figure 3 Effect of cadmium on coupled serine acetyl-transferase and O -acetylserine(thiol)lyase activity in Chlamydomonas reinhardtii (A), Cyanidioschyzon merolae (B), and Synechococcus leopoliensis (C) exposed to 100, 100, and 2 μM Cd(II), respectively, when supplemented with sulfur containing compounds.