Biology subjects

Banta, S.

Publications and source records attributed to Banta, S..

5 recordsLinked to original sources

bioRxiv2026

Biophytometallurgy: biomining metals from plant resources

The physicochemical controls governing metal acquisition, release, and redistribution across biological interfaces remain poorly understood. Biophytometallurgy--the microbially assisted release and recovery of plant-associated metals--was used to probe the directionality of the mechanisms controlling nickel and rare earth element (REE) release from Phytolacca during solid-liquid extraction. Bulk characterization did not support a dominant crystalline REE-phosphate-like host in hydroponically enriched shoots. Dissolution and rebinding experiments instead revealed chemically accessible nickel and REE pools, the latter of which had behaviors consistent with apparent equilibrium-like partitioning under mildly acidic conditions. During sulfur biooxidation, Acidithiobacillus ferrooxidans promoted REE release while providing a competing cell-associated REE sink. Consequently, aqueous REE concentrations reflected net redistribution among the separable plant, solution, and microbial phases instead of dissolution alone. These results establish a framework for studying metal partitioning across complex and coupled biological systems and support a route for aqueous REE recovery from plants without thermochemical conversion to ash.

bioengineering↗

bioRxiv2026

Overexpression of magA in Acidithiobacillus ferrooxidans increases magnetosome production and pyrite bioleaching

Acidithiobacillus ferrooxidans, a chemolithoautotrophic iron- and sulfur-oxidizing acidophile, is a key contributor to industrial-scale copper metal bioleaching. These cells naturally produce magnetosomes, and they may serve as an emerging platform for magnetosome bioproduction, as magnetotactic bacteria (MTB) are difficult to cultivate and to genetically modify. Here we manipulated the expression of the endogenous homologs to the magA and mamB genes in A. ferrooxidans, which are implicated in iron transport required for magnetosome synthesis. Modulation of mamB had no impact on cell behavior. Overexpression of magA increased magnetosome formation and magnetic responsiveness and theses effects were attenuated by CRISPRi knockdown of magA. The augmented magnetosome formation in the magA overexpression cells also led to enhanced bioleaching of pyrite, which is weakly paramagnetic, and this could be further enhanced by addition of an external magnetic field. These results confirm that magA plays a critical role in magnetosome formation in A. ferrooxidans and that magnetosome expression can be enhanced through genetic engineering. In addition, these results demonstrate the potential to improve metal sulfide bioleaching through the manipulation of genes involved in magnetosome formation. TOC Graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=143 SRC="FIGDIR/small/727969v1_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@1ac1822org.highwire.dtl.DTLVardef@1649140org.highwire.dtl.DTLVardef@17c0eccorg.highwire.dtl.DTLVardef@1afa828_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2024

Engineering Candida boidinii formate dehydrogenase for activity with NMN(H)

Multi-step enzymatic reaction cascades often involve cofactors that serve as electron donors/acceptors in addition to the primary substrates. The co-localization of cascades can lead to cross-talk and competition, which can be unfavorable for the production of a targeted product. Orthogonal pathways allow reactions of interest to operate independently from the metabolic reactions within a cell; non-canonical cofactor analogs have been explored as a means to create these orthogonal pathways. Here, we aimed to engineer the formate dehydrogenase from Candid boidinii (CbFDH) for activity with the non-canonical cofactor nicotinamide adenine mononucleotide (NMN(H)). We used PyRosetta and structural alignment to design mutations that enable CbFDH to use NMN+ for the oxidation of formate. Although the suggested mutations did not result in enhanced activity with NMN+, we found that PyRosetta was able to easily design single mutations that disrupted all enzymatic activity.

bioengineering↗

bioRxiv2021

Glutathione synthetase overexpression in Acidithiobacillus ferrooxidans improves halotolerance of iron oxidation

Acidithiobacillus ferrooxidans are well-studied iron- and sulfur-oxidizing acidophilic chemolithoautotrophs that are exploited for their ability to participate in the bioleaching of metal sulfides. Here, we overexpressed the endogenous glutamate--cysteine ligase and glutathione synthetase genes in separate strains and found that glutathione synthetase overexpression increased intracellular glutathione levels. We explored the impact of pH on the halotolerance of iron oxidation in wild type and engineered cultures. The increase in glutathione allowed the modified cells to grow under salt concentrations and pH conditions that are fully inhibitory to wild type cells. These results indicate that glutathione overexpression can be used to increase halotolerance in A. ferrooxidans and would likely be a useful strategy on other acidophilic bacteria. ImportanceThe use of acidophilic bacteria in the hydrometallurgical processing of sulfide ores can enable many benefits including the potential reduction of environmental impacts. The cells involved in bioleaching tend to have limited halotolerance, and increased halotolerance could enable several benefits, including a reduction in the need for fresh water resources. We show that the genetic modification of A. ferrooxidans for the overproduction of glutathione is a promising strategy to enable cells to resist the oxidative stress that can occur during growth in the presence of salt.

bioengineering↗

bioRxiv2021

Computational Structure Prediction Provides a Plausible Mechanism for Electron Transfer by the Outer Membrane Protein Cyc2 from Acidithiobacillus ferrooxidans

Cyc2 is the key protein in the outer membrane of Acidithiobacillus ferrooxidans that mediates electron transfer between extracellular inorganic iron and the intracellular central metabolism. This cytochrome c is specific for iron and interacts with periplasmic proteins to complete a reversible electron transport chain. A structure of Cyc2 has not yet been characterized experimentally. Here we describe a structural model of Cyc2, and associated proteins, to highlight a plausible mechanism for the ferrous iron electron transfer chain. A comparative modeling protocol specific for trans membrane beta barrel (TMBB) proteins in acidophilic conditions (pH ~2) was applied to the primary sequence of Cyc2. The proposed structure has three main regimes: extracellular loops exposed to low-pH conditions, a TMBB, and a N-terminal cytochrome-like region within the periplasmic space. The Cyc2 model was further refined by identifying likely iron and heme docking sites. This represents the first computational model of Cyc2 that accounts for the membrane microenvironment and the acidity in the extracellular matrix. This approach can be used to model other TMBBs which can be critical for chemolithotrophic microbial growth. Importance of workAcidithiobacillus ferrooxidans can oxidize both iron and reduced sulfur compounds and plays a key role in metal sulfide ore bioleaching used for the industrial recovery of metals. A. ferrooxidans has also been explored as a potential organism for emerging technologies such as e-waste recycling and biofuel production. Synthetic biology efforts are hampered by lack of knowledge about the mechanisms of iron oxidation and reduction, which is mediated by the Cyc2 transmembrane beta barrel (TMBB) protein.

bioinformatics↗