Iron homeostasis and responses to iron limitation in extreme acidophiles from the Ferroplasma genus

Abstract Extremely acidophilic archaea from the genus Ferroplasma inhabit iron‐rich biomining environments and are important constituents of naturally occurring microbial consortia that catalyze the production of acid mine drainage. A combined bioinformatic, transcript profiling, and proteomic approach was used to elucidate iron homeostasis mechanisms in “ F. acidarmanus ” Fer1 and F. acidiphilum Y T . Bioinformatic analysis of the “ F. acidarmanus ” Fer1 genome sequence revealed genes encoding proteins hypothesized to be involved in iron‐dependent gene regulation and siderophore biosynthesis; the Fhu and NRAMP cation acquisition systems; iron storage proteins; and the SUF machinery for the biogenesis of Fe‐S clusters. A subset of homologous genes was identified on the F. acidiphilum Y T chromosome by direct PCR probing. In both strains, some of the genes appeared to be regulated in a ferrous/ferric iron‐dependent manner, as indicated by RT‐PCR. A detailed gel‐based proteomics analysis of responses to iron depletion showed that a putative isochorismatase, presumably involved in siderophore biosynthesis, and the SufBCD system were upregulated under iron‐limiting conditions. No evidence was obtained for iron sparing response during iron limitation. This study constitutes the first detailed investigation of iron homeostasis in extremely acidophilic archaea.