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bioRxiv · 10.1101/2020.12.28.424624

Genetic and phylogenetic analysis of dissimilatory iodate-reducing bacteria identifies potential niches across the world's oceans

Reyes-Umana, V.·Henning, Z.·Lee, K.·Barnum, T.·Coates, J.
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Abstract

Iodine is oxidized and reduced as part of a biogeochemical cycle that is especially pronounced in the oceans, where the element naturally concentrates. The use of oxidized iodine in the form of iodate (IO3-) as an electron acceptor by microorganisms is poorly understood. Here, we outline genetic, physiological, and ecological models for dissimilatory IO3- reduction to iodide (I-) by a novel estuarine bacterium, Denitromonas iodocrescerans strain IR-12, sp. nov. Our results show that dissimilatory iodate reduction (DIR) by strain IR-12 is molybdenum-dependent and requires an IO3- reductase (idrA) and likely other genes in a mobile cluster with a conserved association across known and predicted DIR microorganisms (DIRM). Based on genetic and physiological data, IO3- is likely reduced to hypoiodous acid (HIO), which rapidly disproportionates into IO3- and iodide (I-), in a respiratory pathway that provides an energy yield equivalent to that of nitrate or perchlorate respiration. Consistent with the ecological niche expected of such a metabolism, idrA is enriched in the metagenome sequence databases of marine sites with a specific biogeochemical signature and diminished oxygen. Taken together, these data suggest that DIRM help explain the disequilibrium of the IO3-:I- concentration ratio above oxygen minimum zones and support a widespread iodine redox cycle mediated by microbiology.

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Reyes-Umana, V., Henning, Z., Lee, K., Barnum, T., Coates, J.. 2020-12-29. Genetic and phylogenetic analysis of dissimilatory iodate-reducing bacteria identifies potential niches across the world's oceans. https://doi.org/10.1101/2020.12.28.424624

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