Abstract
Acidithiobacillus ferrivorans is an acidophilic bacterium that represents a substantial proportion of the microbial community in a low temperature mining waste stream. Due to its ability to grow at temperatures below 15 °C, it has previously been classified as ‘psychrotolerant’. Low temperature-adapted microorganisms have strategies to grow at cold temperatures such as the production of cold acclimation proteins, DEAD/DEAH box helicases, and compatible solutes plus increasing their cellular membrane fluidity. However, little is known about At. ferrivorans adaptation strategies employed during culture at its temperature extremes. In this study, we report the transcriptomic response of At. ferrivorans SS3 to culture at 8 °C compared to 20 °C. Analysis revealed 373 differentially expressed genes of which, the majority were of unknown function. Only few changes in transcript counts of genes previously described to be cold adaptation genes were detected. Instead, cells cultured at cold (8 °C) altered the expression of a wide range of genes ascribed to functions in transcription, translation, and energy production. It is, therefore, suggested that a temperature of 8 °C imposed little cold stress on At. ferrivorans, underlining its adaptation to growth in the cold as well as suggesting it should be classified as a ‘eurypsychrophile’.Electronic supplementary materialThe online version of this article (doi:10.1007/s00792-016-0882-2) contains supplementary material, which is available to authorized users.
Highlights
Organisms referred to as extremophiles possess genetic traits allowing them to propagate in environments uninhabitable by the majority of microorganisms; be it due to unsuitable pH, temperature, salt or heavy metal concentrations, or other environmental factors (Cowan et al 2015)
Extremely acidophilic microorganisms catalyze the chemical oxidation of metal sulfides by providing ferric iron via oxidation of ferrous iron and protons resulting from metabolism of the generated inorganic
The At. ferrivorans reference genome contains several potential adaptations to a cold life-style that have been previously described in the literature, including genes coding for (a) cold shock proteins (CSPs); (b) molecular chaperones and helicases; (c) cell wall and membrane modification; (d) compatible solute production and transport; (e) oxidative stress regulation; and (f) biofilm formation (Table 1)
Summary
Organisms referred to as extremophiles possess genetic traits allowing them to propagate in environments uninhabitable by the majority of microorganisms; be it due to unsuitable pH, temperature, salt or heavy metal concentrations, or other environmental factors (Cowan et al 2015). The ability to thrive in extreme environments often makes these microorganisms excellent tools for biotechnological applications (reviewed in, e.g., Sarethy et al 2011; Dalmaso et al 2015; Siddiqui 2015). One application of extremophiles is for ‘biomining’, a term that describes the microbial promoted oxidation of insoluble metal sulfides to water soluble salts (Johnson 2014). Extremely acidophilic microorganisms (optimum growth pH ≤3) catalyze the chemical oxidation of metal sulfides by providing ferric iron via oxidation of ferrous iron and protons resulting from metabolism of the generated inorganic. The large temperature differences present at the mine site (minimum air temperature in winter ~−30 °C) have resulted in the development of a microbial community containing species adapted to a range temperatures (Halinen et al 2012)
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