Authors: Anna E. Zhuravleva, I.A. Tsaplina, A.D. Ismailov, L.M. Zakharchuk, G.I. Karavaiko
Abstract: The genus Sulfobacillus includes moderately thermophilic and thermotolerant acidophilic
bacteria, which prefer mixotrophic growth conditions. These organisms are S. thermosulfidooxidans
1269Т, S. sibiricus N1Т and S. thermotolerans Kr1Т. The simultaneous presence of organic (for
example yeast extract) and inorganic energy sources is essential for optimal growth. Carbon sources
are both CO2 and organic compounds. During their mixotrophic growth, the basic pathways of
carbohydrate catabolism of sulfobacilli are those of glycolysis, oxidative pentose phosphate and
Entner–Doudorov (excepting strain N1). Assimilation of CO2 is carried out both auto- and
heterotrophically. Final stages of oxidation of organic substances serve for cell biosynthesis.
Bacteria are able to switch to organo- and autotrophic metabolism. At that the enzyme activities of
pentose phosphate pathway are not detected. The cycle of tricarboxylic acids is disrupted at the
level of 2-oxoglutarate dehydrogenase. The glyoxylate bypass is absent. The maximal protein and
ATP values and high intensity of respiration in S. thermosulfidooxidans, S. sibiricus and S.
thermotolerans cultures were determined under mixotrophic conditions. Studied strains due to their
flexible carbon and energetic metabolism together with other microorganisms of communities
(leptospirilli and archaea) participate in sulfide minerals processing at 40-450C without organic
compounds supplement.
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Authors: Ying Bo Dong, Hai Lin
Abstract: The effects of stresses induced by four ions (potassium, magnesium, aluminum and fluoride ions) on the growth and activity of Acidthiobacillus ferrooxidans LD-1 (At.f LD-1) were investigated. The results showed that these four ions inhibited the growth and activity of At.f LD-1 to different extents. The inhibition effect of these four ion stresses followed the order potassium < magnesium < aluminum < fluoride. The inhibition effects of the trivalent metal ion (aluminum) are greater than divalent (magnesium) and monovalent (potassium) ions at the same concentrations. The inhibition of cations on At.f LD-1 was stronger than that of anions.
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Authors: Sören Bellenberg, Dieu Huynh, Laura Castro, Maria Boretska, Wolfgang Sand, Mario Vera
Abstract: Reactive oxygen species (ROS), such as hydrogen peroxide (H2O2), superoxide (O2-) and hydroxyl radicals (OH.) are known to be formed on the surface of metal sulfides in aqueous solution under oxic and anoxic conditions. Consequently bacteria which have not been adapted to their presence are metabolically inhibited [1], presumably due to the presence of these ROS. Pyrite-grown cells of Acidithiobacillus ferrooxidansT, in contrast to iron (II)-grown cells, were able to oxidize iron (II)-ions or pyrite after 24 h starvation and contact with 1 mM externally added H2O2. In this study, similar results were obtained with Acidiferrobacter sp. SPIII/3. However, Acidithiobacillus ferrivorans SS3 showed the highest tolerance towards contact with H2O2, while Leptospirillum ferrooxidans DSM 2391 was most sensitive. Similar results were obtained after exposure to defined doses of gamma radiation, which cleaves water molecules and generates ROS. In this study members of the three aforementioned genera of mineral-oxidizing bacteria were compared regarding their ability to survive, colonize pyrite and to oxidize iron (II)-ions after exposure to different concentrations of H2O2. Pyrite colonization was studied after exposure to endogenous ROS formed on pyrite or after external addition of H2O2 using confocal laser scanning microscopy (CLSM).
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