Application of capillary electrophoresis combined with conductometric and UV detection to monitor meteorite simulant bioleaching by Acidithiobacillus ferrooxidans

Abstract

The importance of microorganisms and biotechnology in space exploration and future planets colonization has been discussed in the literature. Meteorites are interesting samples to study microbe-mineral interaction focused on space exploration. The chemolithotropic bacterium Acidithiobacillus ferrooxidans has been used as model to understand the iron and sulfur oxidation. In this work, capillary electrophoresis with capacitively coupled contactless conductivity detection and UV detection was used to monitor bacterial growth in a meteorite simulant by measuring the conversion of Fe into Fe . The effect of Co and Ni (metals also found in meteorites) on the bacterial growth was also evaluated. The presented method allowed the analyses of all metals in a single run (less than 8 min). The background electrolyte was composted of 10 mmol/L α-hydroxyisobutyric acid/Histidine. For comparison purpose, the samples were also analyzed by UV-Vis spectrophotometry. The Fe conversion into Fe by A. ferrooxidans was observed up to 36 h with the growth rate constant of 0.19/h and 0.21/h in Tuovinen and Kelly (T&K) and in meteorite simulant media, respectively. The developed method presents favorable prospect to monitor the growth of other chemolithotropic microorganisms for biotechnology applications.

Siderite and vivianite as energy sources for the extreme acidophilic bacterium Acidithiobacillus ferrooxidans in the context of mars habitability

“…However, after the consumption of the initial Fe 2+ , growth rate became limited by the dissolution rate. After the first 24 h, the growth rate observed was μ net = 0.017 ± 0.002 h −1 , similar to the dissolution rate but 11-fold slower than the growth of this strain in its optimal conditions 23 . At the end of the culture, it was observed a 124-fold increase in cell concentration.…”

“…Cultures using T&K medium with only soluble Fe 2+ show the precipitation of Fe 3+ minerals (characterized by its yellow color) after reaching Fe 3+ concentrations up to 100 mM 23 . In the cultures described in the present work, using the siderite medium, the observation of a slow color change began even before the first 24 h period.…”

“…To estimate the presence of the Fe 2+ and Fe 3+ species in solution and in the minerals, colorimetric quantification of both ions were continuously employed according to the methodology described in Gonçalves Silva et al 23 . Complexation of the ferric ion (Fe 3+ ) was performed with a solution of potassium thiocyanate acidified with sulfuric acid, while the ferrous ion (Fe 2+ ) was complexed with the solution of o -phenanthroline buffered with sodium acetate as described by Mendham et al 41 .…”

“…The mineral powders were solubilized in a solution of 1 M of HCl, diluted in MilliQ water and characterized by the methodology described in Gonçalves Silva et al 23 . The ICP OES analyses were carried out in iCAP 6300 Duo ICP optical emission spectrometer (Thermo Fisher Scientific) equipped with axial and radial viewed plasma and a charge injection device detector, which allows measurements from 166.25 to 847.00 nm.…”

“…A. ferrooxidans is a Gram-negative extremophilic bacterium that displays a broad metabolic versatility, capable of living in aerobic and anaerobic conditions and oxidizing different species of reduced sulfur and iron, growing optimally in pH 1.8 to 2.0. Industrially, it is of great importance in biomining and bioleaching processes of copper ores 23 , 24 . The oxidation of high concentrations of iron (as Fe 2+ ) during its growth is associated with the precipitation of minerals including Fe 3+ oxyhydroxides and oxyhydroxide sulfates.…”