Table 4.

Effects of different electron donors and culture conditions on the specific rates of ferrous iron oxidation by Acidithiobacillus spp.

Bacterium and culture medium	Fe2+ oxidation (mg min−1 g protein-1)
AT. FERROOXIDANST
(i) ${\text{S}}_{\text{4}}{\text{O}}_6^{2-}$-grown cultures
+0 Fe2+	69 ± 1.0
+10 μM Fe2+	219 ± 2.0
+100 μM Fe2+	210 ± 4.0
+1000 μM Fe2+	190 ± 7.5
(ii) S0-grown cultures
+0 Fe2+; 10 days	44 ± 8.0
+10 μM Fe2+; 10 days	24 ± 0.6
+100 μM Fe2+; 10 days	38 ± 0.95
+1000 μM Fe2+; 10 days	32 ± 1.5
+0 Fe2+; 21 days	<0.01
(iii) H2-grown cultures
7 days	149 ± 2.0
21 days	210 ± 3.1
+25 mM Fe3+; 5 days*	178 ± 8.3
ACIDITHIOBACILLUS SP. ATCC 33020
(i) ${\text{S}}_{\text{4}}{\text{O}}_6^{2-}$-grown culture
+100 μM Fe2+	45 ± 2.0
(ii) H2-grown cultures
7 days	132 ± 4.8
21 days	225 ± 7.5
+25 mM Fe3+; 5 days*	139 ± 12
+25 mM Fe3+; 14 days*	130 ± 7.0

All cultures were grown aerobically, except those indicated by *, which were grown under anoxic conditions.