The Genus Iodidimonas: From Its Discovery to Potential Applications

The genus Iodidimonas was recently proposed in the class Alphaproteobacteria. Iodidimonas strains are aerobic, mesophilic, neutrophilic, moderately halophilic, and chemo-organotrophic. They were first discovered in natural gas brine water containing a very high level of iodide (I^-). They exhibited a unique phenotypic feature of iodide oxidation to form molecular iodine (I₂). Iodidimonas was also enriched and isolated from surface seawater supplemented with iodide, and it is clearer now that their common habitats are those enriched with iodide. In such environments, Iodidimonas species seem to attack microbial competitors with the toxic form I₂ to occupy their ecological niche. The iodide-oxidizing enzyme (IOX) purified from the Iodidimonas sp. strain Q-1 exhibited high catalytic efficiency for iodide and consisted of at least two proteins IoxA and IoxC. IoxA is a putative multicopper oxidase with four conserved copper-binding regions but is phylogenetically distinct from other bacterial multicopper oxidases. The IOX/iodide system could be used as a novel enzyme-based antimicrobial system which can efficiently kill Bacillus spores. Furthermore, the IOX/iodide system can be applied to the decolorization of recalcitrant dyes, where iodide may function as a novel inorganic natural redox mediator.