The Biofilm Lifestyle of Acidophilic Metal/Sulfur-Oxidizing Microorganisms

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Abstract:At the industrial scale, bioleaching of metal sulfides includes two main technologies, tank leaching and heap leaching. Fluctuations in temperature caused by the exothermic reactions in a heap have a pronounced effect on the growth of microbes and composition of mixed microbial populations. Currently, little is known on the influence of pre-colonized mesophiles or moderate thermophiles on the attachment and bioleaching efficiency by thermophiles. The objective of this study was to investigate the interspecies interactions of the moderate thermophile Sulfobacillus thermosulfidooxidans DSM 9293 T and the thermophile Acidianus sp. DSM 29099 during initial attachment to and dissolution of pyrite. Our results showed that: (1) Acidianus sp. DSM 29099 interacted with S. thermosulfidooxidans T during initial attachment in mixed cultures. In particular, cell attachment was improved in mixed cultures compared to pure cultures alone; however, no improvement of pyrite leaching in mixed cultures compared with pure cultures was observed; (2) active or inactivated cells of S. thermosulfidooxidans T on pyrite inhibited or showed no influence on the initial attachment of Acidianus sp. DSM 29099, respectively, but both promoted its leaching efficiency; (3) S. thermosulfidooxidans T exudates did not enhance the initial attachment of Acidianus sp. DSM 29099 to pyrite, but greatly facilitated its pyrite dissolution efficiency. Our study provides insights into cell-cell interactions between moderate thermophiles and thermophiles and is helpful for understanding of the microbial interactions in a heap leaching environment.

Section: Pure and Mixed Culturesmentioning

confidence: 86%

“…It has been shown that cell attachment to ores as well as biofilm formation is correlated with pyrite leaching by acidophiles [18,50]. A recent study shows that biofilm populations of At.…”

Section: Pure and Mixed Culturesmentioning

confidence: 99%

Influence of Sulfobacillus thermosulfidooxidans on Initial Attachment and Pyrite Leaching by Thermoacidophilic Archaeon Acidianus sp. DSM 29099

Liu

Sand

et al. 2016

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“…A few cells can be visualized on pyrite grain surface after 1 d incubation, and their distribution was heterogeneous ( Figure 1B [14]. It is well known that leaching bacteria prefer to colonize on imperfections of mineral surface, where the crystal structure can be easily destroyed [3,20]. Because of a lack of motility, Sb.…”

Section: Biofilm Formation Of Sb Thermosulfidooxidans On Pyrite Undementioning

confidence: 99%

Enhancement of Biofilm Formation on Pyrite by Sulfobacillus thermosulfidooxidans

Sand

Zhang

2016

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Abstract:Bioleaching is the mobilization of metal cations from insoluble ores by microorganisms. Biofilms can enhance this process. Since Sulfobacillus often appears in leaching heaps or reactors, this genus has aroused attention. In this study, biofilm formation and subsequent pyrite dissolution by the Gram-positive, moderately thermophilic acidophile Sulfobacillus thermosulfidooxidans were investigated. Five strategies, including adjusting initial pH, supplementing an extra energy source or ferric ions, as well as exchanging exhausted medium with fresh medium, were tested for enhancement of its biofilm formation. The results show that regularly exchanging exhausted medium leads to a continuous biofilm development on pyrite. By this way, multiply layered biofilms were observed on pyrite slices, while only monolayer biofilms were visible on pyrite grains. In addition, biofilms were proven to be responsible for pyrite leaching in the early stages.

“…Thus, adhesion and biofilm formation by iron-oxidizing bacteria is essential for an efficient biooxidation or bioleaching of sulfide minerals [16][17][18][19][20]. The EPS mediate cell attachment to minerals as well as electrochemical reactions taking place at mineral surfaces during bioleaching processes [16,19,21]. However, there are few data concerning the adhesion of leaching bacteria like Leptospirillum spp.…”

Section: Introductionmentioning

confidence: 99%

“…Biofilm formation is a prerequisite for efficient bioleaching of minerals [16,21]. Thus, in order to improve bioleaching and better control of biocorrosion the study of EPS structure and function of EPS from bioleaching bacteria is of crucial importance [31].…”

Section: Introductionmentioning

confidence: 99%

Adhesion to Mineral Surfaces by Cells of Leptospirillum, Acidithiobacillus and Sulfobacillus from Armenian Sulfide Ores

Vardanyan¹,

Vardanyan²,

Khachatryan³

et al. 2019

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Bioleaching of metal sulfides is an interfacial process where adhesion and subsequent biofilm formation are considered to be crucial for this process. In this study, adhesion and biofilm formation by several acidophiles (Acidithiobacillus, Leptospirillum and Sulfobacillus) isolated from different biotopes with sulfide ores in Armenia were studied. Results showed that: (1) these bacteria adhere to pyrite surfaces to various extents. A correlation between pyrite biooxidation and adhesion of S. thermosulfidooxidans 6, L. ferriphilum CC, L. ferrooxidans ZC on pyrite surfaces is shown. It is supposed that bioleaching of pyrite by S. thermosulfidooxidans 6, L. ferriphilum CC, L. ferrooxidans ZC occurs by means of indirect leaching: by ferric iron of bacterial origin; (2) cells of At. ferrooxidans 61, L. ferrooxidans ZC and St. thermosulfidooxidans 6 form a monolayer biofilm on pyrite surfaces. The coverage of pyrite surfaces varies among these species. The order of the biofilm coverage is: L. ferrooxidans ZC ≥ At. ferrooxidans 61 > St. thermosulfidooxidans 6; (3) the extracellular polymeric substances (EPS) analysis indicates that the tested strains produce EPS, if grown either on soluble ferrous iron or solid pyrite. EPS are mainly composed of proteins and carbohydrates. Cells excrete higher amounts of capsular EPS than of colloidal EPS. In addition, cells grown on pyrite produce more EPS than ones grown on ferrous iron.