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Role of an archaeal PitA transporter in the copper and arsenic resistance of Metallosphaera sedula an extreme thermoacidophile

ABSTRACT: Thermomacidophilic archaea, such as Metallosphaera sedula, are lithoautotrophs that occupy metal-rich environments. In previous studies, a M. sedula mutant lacking the primary copper efflux transporter, CopA, became copper sensitive. In contrast, the basis for supra-normal copper resistance remained unclear in the spontaneous M. sedula mutant, CuR1. Here, transcriptomic analysis of copper-shocked cultures indicated that CuR1 had a unique regulatory response to metal challenge corresponding to up-regulation of 55 genes. Genome re-sequencing identified 17 confirmed mutations unique to CuR1 that were likely to change gene function. Of these, 12 mapped to genes with annotated function associated with transcription, metabolism or transport. These mutations included 7 non-synonymous substitutions, 4 insertions and 1 deletion. One of the insertion mutations mapped to pseudogene, Msed_1517, and extended its reading frame an additional 209 amino acids. The extended mutant allele was identified as a homolog of Pho4, a family of phosphate symporters that include the bacterial PitA proteins. Orthologs of this allele were apparent in related extremely thermoacidophilic species, suggesting M. sedula was naturally lacking this gene. Phosphate transport studies combined with physiologic analysis demonstrated M. sedula PitA was a low affinity high velocity secondary transporter implicated in copper resistance and arsenate sensitivity. Genetic analysis demonstrated spontaneous arsenate resistant mutants derived from CuR1 all underwent mutation in pitA and non-selectively became copper resistant. Taken together, these results point to archaeal PitA as a key requirement for the increased metal resistance of strain CuR1 and its accelerated capacity for copper bioleaching.

ORGANISM(S): Metallosphaera sedula Metallosphaera sedula DSM 5348

PROVIDER: GSE59253 | GEO | 2014/07/10

SECONDARY ACCESSION(S): PRJNA254817

REPOSITORIES: GEO

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Project description:Thermomacidophilic archaea, such as Metallosphaera sedula, are lithoautotrophs that occupy metal-rich environments. In previous studies, a M. sedula mutant lacking the primary copper efflux transporter, CopA, became copper sensitive. In contrast, the basis for supra-normal copper resistance remained unclear in the spontaneous M. sedula mutant, CuR1. Here, transcriptomic analysis of copper-shocked cultures indicated that CuR1 had a unique regulatory response to metal challenge corresponding to up-regulation of 55 genes. Genome re-sequencing identified 17 confirmed mutations unique to CuR1 that were likely to change gene function. Of these, 12 mapped to genes with annotated function associated with transcription, metabolism or transport. These mutations included 7 non-synonymous substitutions, 4 insertions and 1 deletion. One of the insertion mutations mapped to pseudogene, Msed_1517, and extended its reading frame an additional 209 amino acids. The extended mutant allele was identified as a homolog of Pho4, a family of phosphate symporters that include the bacterial PitA proteins. Orthologs of this allele were apparent in related extremely thermoacidophilic species, suggesting M. sedula was naturally lacking this gene. Phosphate transport studies combined with physiologic analysis demonstrated M. sedula PitA was a low affinity high velocity secondary transporter implicated in copper resistance and arsenate sensitivity. Genetic analysis demonstrated spontaneous arsenate resistant mutants derived from CuR1 all underwent mutation in pitA and non-selectively became copper resistant. Taken together, these results point to archaeal PitA as a key requirement for the increased metal resistance of strain CuR1 and its accelerated capacity for copper bioleaching. The study comprises 5 samples, described in detail below. WT_CuR1: Differential transcriptional response of Metallosphaera sedula DSM 5348, WT, to the supra-normal copper resistant spontaneous Metallosphaera sedula mutant, CuR1 under normal growth conditions. This experiment was done to analyze the differential transcription of WT cells compared with CuR1 cells at mid log phase. WT-15_CuR1-15: Differential transcription of Metallosphaera cells under sub-inhibitory copper challenge (2.0 mM). This experiment was done to analyze the differential transcription of Metallosphaera sedula WT and CuR1 15 minutes post copper challenge. The copper cultures were harvested 15 minutes after the shock. WT-60_CuR1-60: Differential transcription of Metallosphaera cells under sub-inhibitory copper challenge (2.0 mM). This experiment was done to analyze the differential transcription of Metallosphaera sedula WT and CuR1 60 minutes post copper challenge. The copper cultures were harvested 60 minutes after the shock. WT-15_WT-60: Differential transcription of Metallosphaera cells under sub-inhibitory copper challenge (2.0 mM). This experiment was done to analyze the differential transcription of Metallosphaera sedula WT 15 and 60 minutes post copper challenge. The copper cultures were harvested 15 and 60 minutes after the shock, respectively. CuR1-15_CuR1-60: Differential transcription of Metallosphaera cells under sub-inhibitory copper challenge (2.0 mM). This experiment was done to analyze the differential transcription of Metallosphaera sedula CuR1 15 and 60 minutes post copper challenge. The copper cultures were harvested 15 and 60 minutes after the shock, respectively.

Project description:Arsenic is an ubiquitous contaminant and a toxic metalloid which presents two main redox states in nature: arsenite [AsIII] and arsenate [AsV]. Arsenic resistance in Synechocystis sp. strain PCC 6803 is mediated by the arsBHC operon and two additional arsenate reductases encoded by the arsI1 and arsI2 genes. Here we describe the genome-wide responses in response to the presence of arsenate and arsenite in wild type and in mutants in the arsenic resistance system. Both forms of arsenic produced similar responses in the wild type strain including induction of several stress related genes and repression of energy generation processes. The responses observed in the arsB mutant strain were similar to the wild type in short term but were maintained in time while they were only transient in the wild type strain. In contrast, the responses observed in a strain lacking all arsenate reductases (the SARS12 strain) were somewhat different and included lower induction of genes involved in metal homeostasis and Fe-S cluster biogenesis. These results suggest that these two processes are targeted by arsenite in the wild type strain. Finally, analysis of the arsR mutant strain revealed that ArsR seems to only control 5 genes in the genome. Furthermore, over-expression of ArsB conferred hypersentivity to nickel, copper and cadmium in an arsR mutant strain. Analysis of genome-wide gene expression patterns in response to arsenic in WT and mutants involved in arsenic detoxification in the cyanobacterium Synechocystis sp PCC 6803. Cells treated with arsenate or arsenite for 1h. Details: WT cells were treated with 1 mM arsenite for 1 h and its expression profile compared to untreated cells (grown in BG11C media). The effects of arsenate were analyzed in the same way but using a modified BG11C media that constains 15% of the normal phosphate concentration (BG11C low phosphate). A reduction in the phosphate concentration in the media is essential to detect grow inhibition after arsenate addition. In the same way that for arsenite cells were treated with 50 mM arsenate for 1 h and their expression profile was compared to untreated cells. Expression profiles of mutant strains lacking arsB gene (SARSB strain; this strain is hypersensitive to arsenite because it lacks the arsenite exporter) or arsR gene (SARSR strain; this strain expresses the arsBHC constitutively) in control conditions and in response to arsenite addition were also analyzed. In addition the expression profiles of a mutant lacking arsenate reductases (SARS12 strain that has interrupted arsC, arsI1 and arsI2 genes; this strain is hypersensitive to arsenate) were analyzed in both control conditions and after addition of 50 mM arsenate.

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Role of an archaeal PitA transporter in the copper and arsenic resistance of Metallosphaera sedula an extreme thermoacidophile

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