The authors cultivated Wolframiiraptor gerlachensis, a member of a previously uncultivated archaeal lineage from a Nevada hot spring, and showed that it depends on tungsten. Its genome encodes tungsten transporters and tungsten-dependent ferredoxin oxidoreductases, and related genomes from hot springs worldwide suggest the trait is ancestral in this family.
Key numbers
- Spring water contained tungsten at 263 nM, cited by the authors from an earlier measurement; substrate about 0.11 nM and medium components under 0.05 nM (Results).
- Without added tungsten, organism 16S rRNA gene copies fell 100- to 1,000-fold; adding 0.1 or 2 micromolar tungstate restored growth (Fig. 2; Results).
- About 20 nM tungstate was the threshold needed to maintain the organism over at least three transfers (Results; Discussion).
Methods (brief)
Genome-guided cultivation in synthetic media with defined tungstate additions, qPCR and amplicon sequencing, CARD-FISH with nanoSIMS for substrate uptake, ICP-MS and ICP-OES for tungsten in media, and phylogenetic analysis of 78 genomes.
Evidence fitness
Supports statements about tungsten as a growth requirement for certain thermophilic archaea and about tungsten enzymes in microbial ecology. It concerns geothermal microbes, not the human gut, foods or human exposure.
Limitations
Environmental organism in enrichment culture; the spring water value is cited from earlier work. The authors note that under the sulfide-reduced medium tungsten likely occurred as tetrathiotungstate.
Related evidence
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