Papers by Keyword: Microbial Adhesion

Abstract: The adhesion of microorganisms to minerals is one of the least understood aspects of bioleaching processes. Mineral and microorganism type are determinant factors affecting the capacity of a microbial community to form biofilms in these processes. In this paper the adhesion capacity of different microorganisms to different copper sulfide minerals generally present in bioleaching processes was studied. The minerals, chalcosite, chalcopyrite and pyrite were used and the composition of the microbial population which adhered to the mineral surfaces was determined using the Catalyzed Reporter Deposition Fluorescent In Situ Hybridization (CARD-FISH) technique. This technique involves the fluorescent marking of the cells using specific DNA probes and their observation with a confocal microscope. Three probes were used against the microorganisms: Acidithiobacillus ferooxidans, Acidithiobacillus thiooxidans and Leptospirillum. Polished fragments of the three minerals were placed in a tube with a culture medium which was inoculated with cells from a mixed culture capable of growing at 25°C. The adhered microorganisms were counted with CARD-FISH and compared with the total count which was carried out with DAPI staining. The results show that microorganisms adhered indistinctly to pyrite and chalcopyrite but not chalcosite. It was also observed that in pyrite 60% of the adhered microorganisms were Acidithiobacillus thiooxidans, 35% Acidithiobacillus ferrooxidans, and 1 % Leptospirillum. The remaining 4% were unidentified microorganisms.

Abstract: The present project is focused on the plasma-deposition of thin films (~150 nm) containing silver nanoparticles embedded in a polymeric matrix, to prevent microbial adhesion to stainless steel. The process originality relies on a dual strategy associating silver target sputtering and plasma polymerization in argon-hexamethyldisiloxane (HMDSO) plasma, using an asymmetrical RF discharge (13.56 MHz). The physico-chemical properties of the obtained films were investigated by transmission FTIR and XPS. To determine the anti-adhesive efficiency, detachment experiments were performed in a shear stress flow chamber with silver-containing and silver-free deposits. The maximal detachment efficiency was achieved with the polymeric matrix alone. Silver antimicrobial effect is assumed to be related to Ag+ ion progressive release from the embedded particles into the surrounding medium. This release was confirmed by ICP-MS measurements. Furthermore, film biocide activity was observed for silver-containing film.