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  • 1.
    Baker-Austin, Craig
    et al.
    University of East Anglia, UK ; University of Georgia, USA.
    Dopson, Mark
    University of East Anglia, UK ; Umeå University.
    Wexler, Margaret
    University of East Anglia, UK.
    Sawers, R Gary
    John Innes Centre, Norwich, UK.
    Stemmler, Ann
    Wayne State University, School of Medicine, Detroit, USA.
    Rosen, Barry P
    Wayne State University, School of Medicine, Detroit, USA.
    Bond, Philip L
    University of East Anglia, UK ; University of Queensland, Brisbane, Australia.
    Extreme arsenic resistance by the acidophilic archaeon 'Ferroplasma acidarmanus' Fer1.2007In: Extremophiles, ISSN 1431-0651, E-ISSN 1433-4909, Vol. 11, no 3, p. 425-34Article in journal (Refereed)
    Abstract [en]

    'Ferroplasma acidarmanus' Fer1 is an arsenic-hypertolerant acidophilic archaeon isolated from the Iron Mountain mine, California; a site characterized by heavy metals contamination. The presence of up to 10 g arsenate per litre [As(V); 133 mM] did not significantly reduce growth yields, whereas between 5 and 10 g arsenite per litre [As(III); 67-133 mM] significantly reduced the yield. Previous bioinformatic analysis indicates that 'F. acidarmanus' Fer1 has only two predicted genes involved in arsenic resistance and lacks a recognizable gene for an arsenate reductase. Biochemical analysis suggests that 'F. acidarmanus' Fer1 does not reduce arsenate indicating that 'F. acidarmanus' Fer1 has an alternative resistance mechanism to arsenate other than reduction to arsenite and efflux. Primer extension analysis of the putative ars transcriptional regulator (arsR) and efflux pump (arsB) demonstrated that these genes are co-transcribed, and expressed in response to arsenite, but not arsenate. Two-dimensional polyacrylamide gel electrophoresis analysis of 'F. acidarmanus' Fer1 cells exposed to arsenite revealed enhanced expression of proteins associated with protein refolding, including the thermosome Group II HSP60 family chaperonin and HSP70 DnaK type heat shock proteins. This report represents the first molecular and proteomic study of arsenic resistance in an acidophilic archaeon.

  • 2.
    Baker-Austin, Craig
    et al.
    University of East Anglia, UK ; Cefas Weymouth Laboratory, Dorset, UK.
    Potrykus, Joanna
    Umeå University.
    Wexler, Margaret
    University of East Anglia, UK.
    Bond, Philip L
    University of East Anglia, UK ; University of Queensland, Brisbane, Australia.
    Dopson, Mark
    University of East Anglia, UK ; Umeå University.
    Biofilm development in the extremely acidophilic archaeon 'Ferroplasma acidarmanus' Fer1.2010In: Extremophiles, ISSN 1431-0651, E-ISSN 1433-4909, Vol. 14, no 6, p. 485-491Article in journal (Refereed)
    Abstract [en]

    'Ferroplasma acidarmanus' Fer1 is an iron-oxidizing extreme acidophile isolated from the Iron Mountain mine, California, USA. This archaeon is predominantly found in biofilm-associated structures in the environment, and produces two distinct biofilm morphologies. Bioinformatic analysis of the 'F. acidarmanus' Fer1 genome identified genes annotated as involved in attachment and biofilm formation. No putative quorum sensing signaling genes were identified and no N-acyl homoserine lactone-like compounds were found in 'F. acidarmanus' Fer1 biofilm supernatant. Scanning confocal microscopy analysis of biofilm development on the surface of pyrite demonstrated the temporal and spatial development of biofilm growth. Furthermore, two-dimensional polyacrylamide gel electrophoresis was used to examine differential protein expression patterns between biofilm and planktonic populations. Ten up-regulated proteins were identified that included six enzymes associated with anaerobic growth, suggesting that the dominating phenotype in the mature biofilm was associated with anaerobic modes of growth. This report increases our knowledge of the genetic and proteomic basis of biofilm formation in an extreme acidophilic archaeon.

  • 3.
    Christel, Stephan
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Fridlund, Jimmy
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Watkin, Elizabeth L.
    Curtin Univ, Australia.
    Dopson, Mark
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Acidithiobacillus ferrivorans SS3 presents little RNA transcript response related to cold stress during growth at 8 A degrees C suggesting it is a eurypsychrophile2016In: Extremophiles, ISSN 1431-0651, E-ISSN 1433-4909, Vol. 20, no 6, p. 903-913Article in journal (Refereed)
    Abstract [en]

    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 A degrees 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 A degrees C compared to 20 A degrees 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 A degrees 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 A degrees 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'.

  • 4.
    Dopson, Mark
    et al.
    Umeå University ; University of East Anglia, Norwich, UK.
    Baker-Austin, Craig
    University of East Anglia, Norwich, UK ; University of Georgia, Aiken, SC, USA.
    Bond, Philip
    University of East Anglia, Norwich, UK ; Advanced Wastewater Management Centre, University of Queensland, Queensland, Australia.
    Towards determining details of anaerobic growth coupled to ferric iron reduction by the acidophilic archaeon 'Ferroplasma acidarmanus' Fer1.2007In: Extremophiles, ISSN 1431-0651, E-ISSN 1433-4909, Vol. 11, no 1, p. 159-168Article in journal (Refereed)
    Abstract [en]

    Elucidation of the different growth states of Ferroplasma species is crucial in understanding the cycling of iron in acid leaching sites. Therefore, a proteomic and biochemical study of anaerobic growth in 'Ferroplasma acidarmanus' Fer1 has been carried out. Anaerobic growth in Ferroplasma spp. occurred by coupling oxidation of organic carbon with the reduction of Fe(3+); but sulfate, nitrate, sulfite, thiosulfate, and arsenate were not utilized as electron acceptors. Rates of Fe(3+) reduction were similar to other acidophilic chemoorganotrophs. Analysis of the 'F. acidarmanus' Fer1 proteome by 2-dimensional polyacrylamide gel electrophoresis revealed ten key proteins linked with central metabolic pathways > or =4 fold up-regulated during anaerobic growth. These included proteins putatively identified as associated with the reductive tricarboxylic acid pathway used for anaerobic energy production, and others including a putative flavoprotein involved in electron transport. Inhibition of anaerobic growth and Fe(3+) reduction by inhibitors suggests the involvement of electron transport in Fe(3+)reduction. This study has increased the knowledge of anaerobic growth in this biotechnologically and environmentally important acidophilic archaeon.

  • 5.
    Dopson, Mark
    et al.
    Umeå University.
    Lindström, E B
    Umeå University.
    Hallberg, K B
    Umeå University.
    Chromosomally encoded arsenical resistance of the moderately thermophilic acidophile Acidithiobacillus caldus.2001In: Extremophiles, ISSN 1431-0651, E-ISSN 1433-4909, Vol. 5, no 4, p. 247-255Article in journal (Refereed)
    Abstract [en]

    Arsenical resistance is important to bioleaching microorganisms because these organisms release arsenic from minerals such as arsenopyrite during bioleaching. The acidophile Acidithiobacillus caldus KU was found to be resistant to the arsenical ions arsenate, arsenite, and antimony via an inducible, chromosomally encoded resistance mechanism. Because no apparent alteration of the toxic ions was observed, Acidithiobacillus (At.) caldus was tested to determine if it was resistant as a result of decreased accumulation of toxic ions. Reduced accumulation of arsenate and arsenite by induced At. caldus cells supported this hypothesis. It was also found that, with the addition of an energy source, induced At. caldus could transport arsenate and arsenite out of the cell against a concentration gradient. The lack of efflux in the absence of an added energy source and in the presence of inhibitors suggested that efflux was energy dependent. Induced At. caldus also expressed arsenate reductase activity, indicating that At. caldus has an arsenical resistance mechanism that is analogous to previously described systems from other Bacteria. Southern hybridization analysis showed that At. caldus and other gram-negative acidophiles carry an Escherichia coli arsB homologue on the chromosome.

  • 6.
    Dopson, Mark
    et al.
    Umeå University.
    Lindström, E Börje
    Umeå University.
    Hallberg, Kevin B
    University of Wales, Bangor, Gwynedd, UK.
    ATP generation during reduced inorganic sulfur compound oxidation by Acidithiobacillus caldus is exclusively due to electron transport phosphorylation.2002In: Extremophiles, ISSN 1431-0651, E-ISSN 1433-4909, Vol. 6, no 2, p. 123-129Article in journal (Refereed)
    Abstract [en]

    The synthesis of adenosine 5-triphosphate (ATP) (increase in phosphorylation potential) during the oxidation of reduced inorganic sulfur compounds was studied in the moderately thermophilic acidophileAcidithiobacillus caldus (strain KU) (formerly Thiohacillus caldus). The phosphorylation potential increased during the oxidation of all reduced inorganic sulfur compounds tested compared with resting cells. The generation of ATP in whole cells was inhibited by the F0F1 ATPase inhibitor oligomycin, electron transport chain inhibitors, valinomycin and potassium ions. There was no increase in the phosphorylation potential, nor synthesis of ATP. in the absence of electron transport. An apparent lack of substrate-level phosphorylation was indicated by the lack of adenosine 5-phosphosulfate reductase in tetrathionate-grown At. caldus. Studies were also performed on the synthesis of ATP by membrane vesicles of At. caldus when presented with an artificial proton gradient. Complete inhibition of ATP synthesis in these vesicles occurred when they were loaded with N,N-dicyclohexylcarbodiimide (DCCD), but not when they were loaded with oligomycin, vanadate or electron transport chain inhibitors. The data presented here suggest that during the oxidation of reduced inorganic sulfur compounds by At. caldus, all ATP is synthesized by oxidative phosphorylation via a membrane-bound F0F1 ATPase driven by a proton gradient.

  • 7. Mangold, Stefanie
    et al.
    Potrykus, Joanna
    Bjorn, Erik
    Lovgren, Lars
    Dopson, Mark
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Extreme zinc tolerance in acidophilic microorganisms from the bacterial and archaeal domains2013In: Extremophiles, ISSN 1431-0651, E-ISSN 1433-4909, Vol. 17, no 1, p. 75-85Article in journal (Refereed)
    Abstract [en]

    Zinc can occur in extremely high concentrations in acidic, heavy metal polluted environments habited by acidophilic prokaryotes. Although these organisms are able to thrive in such severely ntaminated ecosystems their resistance mechanisms have not been well studied. Bioinformatic alysis of a range of acidophilic bacterial and archaeal genomes identified homologues of several own zinc homeostasis systems. These included primary and secondary transporters, such as the imary heavy metal exporter ZntA and Nramp super-family secondary importer MntH. Three idophilic model microorganisms, the archaeon 'Ferroplasma acidarmanus', the Gram negative cterium Acidithiobacillus caldus, and the Gram positive bacterium Acidimicrobium ferrooxidans, were lected for detailed analyses. Zinc speciation modeling of the growth media demonstrated that a large action of the free metal ion is complexed, potentially affecting its toxicity. Indeed, many of the tative zinc homeos! asis genes were constitutively expressed and with the exception of 'F. acidarmanus' ZntA, they were t up-regulated in the presence of excess zinc. Proteomic analysis revealed that zinc played a role in idative stress in At. caldus and Am. ferrooxidans. Furthermore, 'F. acidarmanus' kept a constant level intracellular zinc over all conditions tested whereas the intracellular levels increased with increasing nc exposure in the remaining organisms.

  • 8. Mangold, Stefanie
    et al.
    Rao Jonna, Venkateswara
    Dopson, Mark
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Response of Acidithiobacillus caldus toward suboptimal pH conditions.2013In: Extremophiles, ISSN 1431-0651, E-ISSN 1433-4909, Vol. 17, no 4, p. 689-696Article in journal (Refereed)
    Abstract [en]

    Maintenance of a circumneutral intracellular pH is important for any organism. Acidophilic microorganisms thrive at low pH while maintaining their intracellular pH around 6.5. However, the mechanisms contributing to acidophile pH homeostasis are not well characterized. The authors investigated the proteomic response and cytoplasmic membrane fatty acid profiles of Acidithiobacillus caldus toward three pH values: 1.1, 2.5, and 4.0. Major rearrangements were observed but lower pH elicited larger changes. Differentially expressed transcription factors suggested tight transcriptional control of pH induced genes. Enzymes involved in sulfur metabolism were up-regulated at pH 1.1 suggesting either that: (1) cells required more energy for maintenance or (2) increased metabolic activity was a specific acid stress response to export intracellular protons via 1° electron transport proton pumps. Furthermore, glutamate decarboxylase, an important enzyme in Escherichia coli acid resistance, was uniquely expressed at pH 1.1. Other proteins previously shown to be involved in neutrophilic acid response, such as spermidine synthase, PspA, and toluene tolerance protein, were differentially expressed in At. caldus but require further investigation to show a direct link to pH homeostasis. Their roles in acidophilic organisms are discussed. Active modulation of fatty acid profiles was detected and suggested a more rigid membrane at low pH.

1 - 8 of 8
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