Inhibition of Iron-oxidizing Activity by Bisulfite Ion inThiobacillus ferrooxidans

Sulfite Oxidation Catalyzed byaa3-Type CytochromecOxidase inAcidithiobacillus ferrooxidans

“…23) In contrast, A. ferrooxidans strain AP19-3 is the most sensitive to sulfite among the strains tested. 18,20,24,25,32,33,38) Sulfite oxidase activities were compared with cytochrome c oxidases purified from A. ferrooxidans strains D3-2, ATCC 23270, MON-1, and AP19-3 as enzyme sources. The purification steps used for the cytochrome c oxidases of strains ATCC 23270, MON-1, and AP19-3 were the same as those used for strain D3-2.…”

“…23) Sulfite is an intermediate produced during sulfur oxidation in y To whom correspondence should be addressed. Tel/Fax: +81-86-251-8306; E-mail: sugio@cc.okayama-u.ac.jp A. ferrooxidans and is harmful to iron oxidase and SFORase, 13,[15][16][17]21,[24][25][26][27][28] but there have been few reports on the enzyme involved in sulfite oxidation in A. ferrooxidans. Sulfite oxidase (sulfite:cytochrome c oxidoreductase) which uses horse-heart cytochrome c and ferricyanide as electron acceptors, was partially purified from sulfur-grown Thiobacillus ferrooxidans.…”

Isolation and Characterization ofAcidithiobacillus ferrooxidansStrain D3-2 Active in Copper Bioleaching from a Copper Mine in Chile

“…In this study, we found for the first time that A. ferrooxidans strain D3-2 has a unique sulfite oxidase resistant to a high concentration of sulfite ion that shows maximum activity at 8 mM of sodium bisulfate, while A. ferrooxidans ATCC 23270 has a sulfite oxidase sensitive to sulfite ion that is completely inhibited by 1 mM of sodium bisulfite. Since it is known that sulfite ion is a toxic intermediate during sulfur oxidation in A. ferrooxidans cells and, that it strongly inhibits iron oxidase activity, [12][13][14][15]18,19,[23][24][25][26][27] A. ferrooxidans strains that have a sulfite resistant-sulfite oxidase are supposedly able to grow and solubilize more copper from chalcopyrite (CuFeS 2 ) than strain ATCC 23270, which has a sulfite-sensitive sulfite oxidase, because in the bioleaching process, A. ferrooxidans cells must coexist for a long time, more than a month, with toxic sulfite ions produced by the oxidation of CuFeS 2 . In this study, we also found for the first time that strain D3-2, but not strain ATCC 23270, grew and solubilized Cu 2þ in 1% chalcopyrite-concentrate medium supplemented with 5 mM of sodium bisulfite.…”

“…The ion is highly toxic in A. ferrooxidans cells, and strongly inhibits cell growth by inhibiting components of the iron oxidase enzyme system, such as cytochrome c oxidase. [23][24][25][26][27][29][30][31] The sulfite oxidase activities of strains D3-2, D3-6, and ATCC 23270 were 5.8, 2.9, and 1.0, ml O 2 uptakeÁmg protein À1 Ámin À1 (Fig. 4C).…”

“…During an attempt to find a clue as to on these unexpected results, we found that strain D3-2 has a unique sulfite oxidase differing greatly from A. ferrooxidans strain ATCC 23270, in that the sulfite oxidase of strain D3-2 was more highly resistant to sulfite ions than that of ATCC 23270. Since it has been found that the sulfite ion is a highly toxic intermediate produced during sulfur oxidation by A. ferrooxidans cells, [23][24][25][26][27] and that it strongly inhibits the growth of A. ferrooxidans cells by inhibiting one of the most important components of iron oxidase and aa 3 -type cytochrome c oxidase, 25,26,[29][30][31] strain D3-2, with sulfite resistant-sulfite oxidase, appears to be more advantageous for Cu-bioleaching than strain ATCC 23270, with a sulfite-sensitive sulfite oxidase, because chalcopyrite (CuFeS 2 ) contains much sulfur in the ore and the bioleaching process for chalcopyrite requires a long time, more than a month. Hence, during the process, A. ferrooxidans cells are continuously placed in a sulfite-rich environment.…”