Abstract
A novel strain of an iron- and sulfur-oxidizing bacterium was isolated from a natural biotope at Kashen copper ore (Martakert Province, Republic of Artsakh). The strain is able to grow and oxidize ferrous ions in the range of pH 1.4–2.6 with optimal pH 2.0. The optimal temperature for growth is 35°C. Acidithiobacillus sp. Ksh has shown the highest activity for pyrite oxidation among other strains. It also demonstrated high activity in oxidation for copper and copper-gold bearing ores (Armenia). The isolate Acidithiobacillus sp. Ksh was identified as Acidithiobacillus ferrooxidans based on phylogenetic and physiological studies. Comparative studies of EPS production by cells grown on ferrous ions or pyrite were carried out. The chemical composition of capsular and colloidal EPS produced by Acidithiobacillus (At.) ferrooxidans Ksh were revealed to be proteins and carbohydrates. Exosaccharide produced by At. ferrooxidans Ksh is present mainly as polysaccharide in contrast to Leptospirillum (L.) ferriphilum CC, which is oligosaccharide. The structural difference of colloidal particles of these polysaccharides was due to the degree of hydration of the saccharide molecules.
Highlights
Metal bioleaching technology is the use of sulfur- and/or iron-oxidizing bacteria and archaea to extract valuable metals from metal sulfides (MS)
It has been deposited in the Republican Centre for Deposition of Microorganisms of the National Academy of Sciences and Ministry of Education and Science of Armenia under the number MDC7056
Further studies have shown that the cells of At. ferrooxidans Ksh produce much higher amounts of total extracellular polymeric substances (EPS), if grown on pyrite, compared to the ones grown on ferrous ions
Summary
Metal bioleaching technology is the use of sulfur- and/or iron-oxidizing bacteria and archaea to extract valuable metals from metal sulfides (MS). The current well-accepted mechanism for MS oxidation is the indirect “contact” leaching (Sand et al, 2001; Vera et al, 2013). Microbial interactions with MS including microbial adhesion on MS and biofilm development are of both fundamental and practical importance (Vera et al, 2013; Li et al, 2020). The matrix represents compounds of extracellular polymeric substances (EPS) which include carbohydrates, proteins, lipids, eDNA, etc. Biofilms and EPS mediate adhesion of cells onto substrates or material surfaces, and protect cells from harsh conditions, e.g., desiccation or oxidative stress (Karamanev, 1991; Yu et al, 2008; Bellenberg et al, 2019)
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