Post by fathihabashi1928 on Apr 10, 2008 2:49:29 GMT
There has been a long discussion in the past few decades regarding bacterial action on sulphide minerals [1]. Two theories were put forward: the direct action of the bacterial on the mineral and the indirect action namely by the chemical reaction of Fe3+ ion with the mineral and the bacterial action is simply catalyzing the regeneration of Fe3+ iron by enhancing the oxidation of Fe2+ formed.
A recent work by Y. Konishi et al [2,3] at the University of Osaka Prefecture in Japan strongly suggests that the direct action of the microorganism on the mineral plays the leading role. The work was aimed at the production of nano metallic particles and involves the reduction of gold and platinum chloro complex in acidic medium by the anaerobic bacterium Shewanella algae. When the bacteria were contacted with the solution containing the metal ions and a reducing agent, it was found that metallic gold and metallic platinum were deposited in the periplasmic space of the bacterial cell. This means that both the metal ion and the reducing agent diffused through the cell outer membrane, reacted in the periplasmic space forming metallic particles which could not diffuse out because they are insoluble. The reaction being catalyzed by the metabolic products of the microorganism.
Fig. 1- Cross section of Shewanella algae showing metallic gold particles deposited in the periplasmic space of the cell Fig. 2 - Cross section of Shewanella algae showing metallic nano particles of metallic platinum deposited in the periplasmic space of the cell
Figure 1 shows the deposited gold particles in the periplasmic space from HAuCl4 solution while Figure 2 shows the deposited platinum from H2PtCl6 solution. In case of the reaction of Thiobacillus thiooxidans with sulphide minerals it would be expected that both the metal ion generated from the sulphide mineral
MS = M2+ + S2- K = [M2+] [S2-] = 10-30
and oxygen diffuse through the outer cell membrane, react forming sulphate ion
S2- + 2 O2 = SO4
which then diffuses out of the cell membrane. The above reaction being catalyzed by the metabolic products of the microorganism, thus confirming the direct action mechanism. Comments are welcome.
[1] F. Habashi, How Do Bacteria Interact with Minerals?, Minerals Engineering 15, 307¡V308 (2002).
[2] Y. Konishi et al., Intracellular Recovery of Gold by Microbial Reduction of AuCl4- Ions Using the Anaerobic Bacterium Shewanella algae, Hydrometallurgy 81, 24-29 (2006).
[3] Y. Konishi et al., Bioreductive Deposition of Platinum Nanoparticles on the Bacterium Shewanella algae, J. Biotechnology 128,648-653(2007)
A recent work by Y. Konishi et al [2,3] at the University of Osaka Prefecture in Japan strongly suggests that the direct action of the microorganism on the mineral plays the leading role. The work was aimed at the production of nano metallic particles and involves the reduction of gold and platinum chloro complex in acidic medium by the anaerobic bacterium Shewanella algae. When the bacteria were contacted with the solution containing the metal ions and a reducing agent, it was found that metallic gold and metallic platinum were deposited in the periplasmic space of the bacterial cell. This means that both the metal ion and the reducing agent diffused through the cell outer membrane, reacted in the periplasmic space forming metallic particles which could not diffuse out because they are insoluble. The reaction being catalyzed by the metabolic products of the microorganism.
Fig. 1- Cross section of Shewanella algae showing metallic gold particles deposited in the periplasmic space of the cell Fig. 2 - Cross section of Shewanella algae showing metallic nano particles of metallic platinum deposited in the periplasmic space of the cell
Figure 1 shows the deposited gold particles in the periplasmic space from HAuCl4 solution while Figure 2 shows the deposited platinum from H2PtCl6 solution. In case of the reaction of Thiobacillus thiooxidans with sulphide minerals it would be expected that both the metal ion generated from the sulphide mineral
MS = M2+ + S2- K = [M2+] [S2-] = 10-30
and oxygen diffuse through the outer cell membrane, react forming sulphate ion
S2- + 2 O2 = SO4
which then diffuses out of the cell membrane. The above reaction being catalyzed by the metabolic products of the microorganism, thus confirming the direct action mechanism. Comments are welcome.
[1] F. Habashi, How Do Bacteria Interact with Minerals?, Minerals Engineering 15, 307¡V308 (2002).
[2] Y. Konishi et al., Intracellular Recovery of Gold by Microbial Reduction of AuCl4- Ions Using the Anaerobic Bacterium Shewanella algae, Hydrometallurgy 81, 24-29 (2006).
[3] Y. Konishi et al., Bioreductive Deposition of Platinum Nanoparticles on the Bacterium Shewanella algae, J. Biotechnology 128,648-653(2007)