Interactions Between Cells of Sulfobacillus thermosulfidooxidans and Leptospirillum ferriphilum During Pyrite Bioleaching.

Qian Li,Tangfu Xiao,Ruiyong Zhang,Jianyu Zhu,Shoupeng Li,Wolfgang Sand

doi:10.3389/fmicb.2020.00044

Abstract

Sulfobacillus and Leptospirillum occur frequently in leaching systems. Here we investigated the effects of cells of L. ferriphilum on biofilm formation and leaching performance by S. thermosulfidooxidans. The effects were caused by the presence of L. ferriphilum or an addition of pyrite leach liquor from L. ferriphilum. Data show that the number of attached S. thermosulfidooxidans on pyrite increases, if the pyrite had been pre-colonized by living biofilms of L. ferriphilum, while it decreases if the pre-colonized biofilms had been inactivated. Coaggregation between S. thermosulfidooxidans and L. ferriphilum occurs during the dual-species biofilm formation, but different effects on bioleaching were noted, if the preculture of L. ferriphilum had been different. If L. ferriphilum had been pre-colonized on a pyrite, significantly negative effect was shown. However, if the two species were simultaneously inoculated into a sterile leaching system, the bioleaching efficiency was better than that of a pure culture of S. thermosulfidooxidans. The effect might be related to a metabolic preference of S. thermosulfidooxidans. If S. thermosulfidooxidans performed leaching in a filtered pyrite leachate from L. ferriphilum, the cells preferred to oxidize RISCs instead of ferrous ion and the number of attached cells decreased compared with the control. This study gives an indication that in a short-term multi-species leaching system the role of S. thermosufidooxidans may be related to the time of its introduction.

Highlights

Microorganisms catalyze metal ion leaching from insoluble metal sulfides, such as pyrite (FeS2), arsenopyrite (FeAsS), chalcopyrite (CuFeS2), sphalerite (ZnS) or marcasite (FeS2) by biological oxidation via contact and non-contact modes
Ferrous ion is re-oxidized to ferric ion by the iron-oxidizing microorganisms, and reduced inorganic sulfur compounds (RISCs) are oxidized to sulfate by sulfuroxidizing bacteria
The results show that the number of attached S. thermosulfidooxidans on pyrite increased, if the pyrite was pre-colonized by living biofilms of L. ferriphilum, while it decreased if the biofilms had been inactivated previously

Summary

INTRODUCTION

Microorganisms catalyze metal ion leaching from insoluble metal sulfides, such as pyrite (FeS2), arsenopyrite (FeAsS), chalcopyrite (CuFeS2), sphalerite (ZnS) or marcasite (FeS2) by biological oxidation via contact and non-contact modes. The pH range for their growth is 1.1–5.5, with an optimum between 1.7 and 2.4 (Bogdanova et al, 2006) They can oxidize ferrous ion, reduced RISCs such as tetrathionate, thiosulfate and elemental sulfur, as well as sulfide minerals in the presence of 0.02% yeast extract. They always are members of microbial leaching communities because of their versatile metabolism and because of their high tolerance to low pH and high metal concentrations (Rawlings and Johnson, 2007). When S. thermosulfidooxidans performed leaching in filtered leachate from L. ferriphilum, a high percentage of ferrous ion and low pH of the system illustrate it preferred to oxidize RISCs over ferrous ion, and numbers of attached cells decreased compared with the control. Our study provides information for investigating species-species interactions in a bioleaching system, which is helpful for researchers to optimize a leaching consortium or to prevent bioleaching happening in natural environment

MATERIALS AND METHODS

RESULTS AND DISCUSSION

DATA AVAILABILITY STATEMENT