Extracellular polymeric substances (EPS) production in sulfobacillus thermosulfidooxidans and its relevance on attachment to metal sulfides

Abstract. Retrieving metals from sulphide minerals has been a key step for the mining industry through many years. There are microorganisms that colonize mining areas and ore deposits and are able to use some of the compounds of the ores to obtain energy, precipitating some other components. The use of acidophilic leaching bacteria, in a process known as biohydrometallurgy, has become an alternative way to traditional mining allowing the recovery of metals. Biohydrometallurgy has shown to be environmentally friendly and it has shown to be cheaper compared to conventional mining (pyrometallurgy). In nature, microorganisms are able to build structures such as biofilms that confer resistance to microorganisms under adverse environmental conditions. Those are communities of microorganisms, embedded in extracellular polymeric substances (EPS). The EPS also enhances a reaction space by extracellular biochemical reaction; in leaching organisms it has been observed that biofilms composed of EPS play a key role in degradation of ores. Sulfobacillus thermosulfidooxidans is a moderate thermophile used in bioleaching, nevertheless little is known about S. thermosulfidooxidans and the nature and composition of its EPS. The use of S. thermosulfidooxidans in biomining is promising because it is an exothermal reaction and it reaches high temperatures. With the idea of using this bacterium in the future for biomining process, its growth was studied in the presence of different energy substrates, the composition of its EPS and by bioinformatics, some genes potentially involved in the process of EPS production. The growth of S. thermosulfidooxidans changes according to the energy source used in the medium, the maximum cell concentration was achieved in medium with iron sulphate as energy source. S. thermosulfidooxidans is able to grow under heterotrophic and mixotrofic conditions, nevertheless growth under mixotrophic conditions is higher than under heterotrophic conditions. Attachment to sulfur and pyrite surfaces was followed by Confocal Laser Scaning Microscope (CLSM) along time. Attachment to piryte surfaces seems to be faster since cell agglomeration over reduced spaces can be seen earlier than in sulfur surfaces. The EPS produced by S. thermosulfidooxidans grown in different energy sources, sulfur, pyrite and iron sulphate was extracted and analyzed. The EPS composition was determined, the proportion of its components changed according to the energy source and humic acids were found to be one of the major components. It was observed that EPS production diminishes in the planktonic culture and it was not detectable in some cases. Staining with labeled lectins was made in order to visualize and identify some components of its EPS; it was observed that also the components of the EPS changes not only depending on the energy source tested, pyrite and sulfur, but also in the planktonic and sessile state of the cells. Only concanavalin A had a positive interaction under all the conditions tested. Genes previously reported to be involved in EPS synthesis and biofilm formation, were searched on S. thermosulfidooxidans DSM 9293 genome but no meaningful matches were found. Thus, sequences coding for proteins related to the mechanisms of production and exportation of EPS were searched on the genome and ABC transporters were found and selected for amplification. However, no successful amplification or measurement of level of expression of these genes was achieved.

• Autores: Aguirre Morales, Mauricio
• Fecha de publicación: 2012
• Institución: Universidad Nacional de Colombia
• Repositorio: Universidad Nacional de Colombia
• Idioma: spa
• OAI Identifier: oai:repositorio.unal.edu.co:unal/20225
• Acceso en línea: https://repositorio.unal.edu.co/handle/unal/20225; http://bdigital.unal.edu.co/10705/
• Palabra clave: 54 Química y ciencias afines / Chemistry; 57 Ciencias de la vida; Biología / Life sciences; biology; 66 Ingeniería química y Tecnologías relacionadas/ Chemical engineering; Bioleaching; Extracellular polymeric substances; Biofilm; Sulfobacillus thermosulfidooxidans.; Biolixiviacion; Sustancias poliméricas extracelulares; Sulfobacillus thermosulfidooxidans
• Rights: openAccess
• License: Atribución-NoComercial 4.0 Internacional