Isolation of a Dissimilatory Iodate-Reducing From a Freshwater Creek in the San Francisco Bay Area.

Recent reports of dissimilatory iodate-reducing microorganisms (DIRM) have arisen from studies of bacteria in marine environments. These studies described the physiology and distribution of DIRM while also demonstrating their presence in iodine-rich marine environments. We posited that despite lower iodine concentrations, terrestrial and freshwater ecosystems should also harbor DIRM. We established numerous enrichments from coastal and freshwater environments that actively remove amended iodate. We describe the physiology and genome of a new DIRM isolate, sp. TC-10, emerging from a freshwater creek microcosm. Like other DIRM, sp. TC-10 couples acetate oxidation to iodate reduction with a concomitant increase in the OD. Our results indicate that sp. TC-10 performs dissimilatory iodate reduction (DIR) using the recently described iodate reductase (Idr). We provide further evidence of horizontal gene transfer of the genes by demonstrating the lack of Idr in the closely related (99.93% 16S rDNA sequence identity) sp. MF63 and describe the heterogeneity of the accessory proteins associated with the iodate reduction island (IRI). These observations provide additional evidence that DIR is a horizontally acquired metabolism with broad environmental distribution beyond exclusively marine environments.