Manipulation of pyrite colonization and leaching by iron-oxidizing Acidithiobacillus species

Abstract

In this study, the process of pyrite colonization and leaching by three iron-oxidizing Acidithiobacillus species was investigated by fluorescence microscopy, bacterial attachment, and leaching assays. Within the first 4-5 days, only the biofilm subpopulation was responsible for pyrite dissolution. Pyrite-grown cells, in contrast to iron-grown cells, were able to oxidize iron(II) ions or pyrite after 24 h iron starvation and incubation with 1 mM H₂O₂, indicating that these cells were adapted to the presence of enhanced levels of reactive oxygen species (ROS), which are generated on metal sulfide surfaces. Acidithiobacillus ferrivorans SS3 and Acidithiobacillus ferrooxidans R1 showed enhanced pyrite colonization and biofilm formation compared to A. ferrooxidans (T). A broad range of factors influencing the biofilm formation on pyrite were also identified, some of them were strain-specific. Cultivation at non-optimum growth temperatures or increased ionic strength led to a decreased colonization of pyrite. The presence of iron(III) ions increased pyrite colonization, especially when pyrite-grown cells were used, while the addition of 20 mM copper(II) ions resulted in reduced biofilm formation on pyrite. This observation correlated with a different extracellular polymeric substance (EPS) composition of copper-exposed cells. Interestingly, the addition of 1 mM sodium glucuronate in combination with iron(III) ions led to a 5-fold and 7-fold increased cell attachment after 1 and 8 days of incubation, respectively, in A. ferrooxidans (T). In addition, sodium glucuronate addition enhanced pyrite dissolution by 25%.

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

“…DSM 29099. This is, however, in contrast to the previous study indicating that attachment of Acidithiobacillus was promoted by addition of 1 mM iron(III) ions, especially when cells were pre-grown on pyrite [35]. When incubated with S. thermosulfidooxidans T exudates, 57% of the cells of Acidianus sp.…”

“…ferrooxidans T are responsible for pyrite dissolution at the early stage (first 4-5 days). However, planktonic cells are contributing substantially later on in the bioleaching process [35]. Thus, it is not surprising that the initial attachment of Acidianus sp.…”

Enhancement of Biofilm Formation on Pyrite by Sulfobacillus thermosulfidooxidans

“…The complexed iron ions in EPS provide a positive charge on the cell surface inducing cells to adhere to negatively charged pyrite surfaces via electrostatic attract forces [3,27]. It has been shown that a supplement of 1 mM ferric ions causes a 10 fold increase of the colonization of pyrite by cells of A. ferrooxidans R1 [25]. In our study, ferric ions did not increase adhesion of Sb.…”

“…thermosulfidooxidans due to exchanging spent medium may be due to several reasons. One is that the organic supplement facilitates the growth of A recent study indicated that not planktonic but biofilm cells of Acidithiobacillus ferrooxidans T made contributions to pyrite dissolution within the first 4-5 days after inoculation [25]. Accordingly, we may speculate that biofilms of Sb.…”

Optimization of Lithotrophic Activities of Acidithiobacillus ferrooxidans toward Significant Reduction of Sulfur and Ash from Low Rank Bitumen

“…Several attempts have been made to explain the direct attack of A. ferrooxidans on the metal sulfides. It can be considered as a heterogeneous process which the bacterial cell attaches itself to the sulfide crystal surface and the corrosion occurs in a thin film located in the interface between the bacterial outer membrane and the sulfide surface (Acharya et al 2004;Bellenberg et al 2015;Manisha et al 2000;Rodriguez et al 2003 …”