Biogeography of thermophiles and predominance of Thermus scotoductus in domestic water heaters
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Built systems such as water heaters can harbor extremophiles similar to those residing in natural hot springs, but the extent of colonization is not well understood. To address this, we conducted a survey of thermophilic microorganisms in household water heaters across the United States. Filter samples and inoculated cultures were collected by citizen-scientists from 101 homes. Draft genomes were assembled from cultured isolates and 16S rRNA genes were sequenced from filter samples. 28% of households harbored communities with unambiguous DNA signatures of thermophilic organisms, 36% of households provided viable inocula, and 21% of households had both. All of the recovered cultures as well as the community sequencing results revealed Thermus scotoductus to be the dominant thermophile in domestic water heaters, with a minority of water heaters also containing Meiothermus species and a few containing Aquificae. Sequence distance comparisons show that allopatric speciation does not appear to be a strong control on T. scotoductus distribution. Our results demonstrate that thermophilic organisms are widespread in hot tap water, and that Thermus scotoductus preferentially colonizes water heaters at the expense of local environmental Thermus strains.
KeywordsThermophiles Biogeography Microbial ecology Citizen science Built environment
This work was supported by NASA Astrobiology Institute cooperative agreement #NNA09DA76A. The citizen-science outreach was conducted by Pennsylvania Space Grant with assistance from the National Space Grant Consortium. We thank Heather Nelson, who helped facilitate the citizen science project. The work was funded by the NASA Astrobiology Institute (via the Penn State Astrobiology Research Center) and NASA's National Space Grant College and Fellowship Program (via the Pennsylvania Space Grant Consortium).
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Conflict of interests
The authors declare that there are no conflicts of interests regarding the publication of this paper.
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