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Iodate reduction by dissimilatory iodate-reducing microorganisms (DIRMs) plays a crucial role in the biogeochemical cycling of iodine on Earth. However, the occurrence and distribution of DIRMs in iodine-rich groundwater remain unclear. In this study, we isolated the dissimilatory iodate-reducing bacterium Azonexus hydrophilus strain NCP973 from a geogenic high-iodine groundwater of China for the first time. The analysis of genome, transcriptome, and heterologous expression revealed that strain NCP973 uses the dissimilatory iodate-reducing enzyme IdrABP1P2 to reduce dissolved or in situ sediment-bound iodate to iodide. The location of IdrABP1P2 in the conjugative plasmid of strain NCP973 implies that IdrABP1P2 could be spread by horizontal gene transfer and allow the recipient microorganisms to participate in the enrichment of iodide in aquifers. Based on the global iodine-rich groundwater metagenomes and genomes, the identification of idrA showed that phylogenetically diverse DIRMs are widely distributed not only in geogenic high-iodine groundwater of China but also in radionuclide-contaminated groundwater of USA as well as in subsurface cavern waters in Germany and Italy. Moreover, the abundance of idrA was found to be higher in groundwater with a relatively high iodine content. Collectively, these results suggest that terrestrial iodine-affected groundwater systems are another important habitat for DIRMs in addition to marine environments, and their activity in aquifers triggers the mobilization and enrichment of iodine in groundwater worldwide.

Extracellular iodate reduction by Shewanella spp. contributes to iodide generation in the biogeochemical cycling of iodine. However, there is a disagreement on whether Shewanella spp. use different extracellular electron transfer pathways with dependence on electron donors in iodate reduction. In this study, a series of gene deletion mutants of Shewanella oneidensis MR-1 were created to investigate the roles of dmsEFABGH , mtrCAB, and so4357-so4362 operons in iodate reduction. The iodate-reducing activity of the mutants was tested with lactate, formate, and H 2 as the sole electron donors, respectively. In the absence of single- dms gene, iodate reduction efficiency of the mutants was only 12.9%-84.0% with lactate at 24 hours, 22.1%-85.9% with formate at 20 hours, and 19.6%-57.7% with H 2 at 42 hours in comparison to complete reduction by the wild type. Progressive inhibition of iodate reduction was observed when the dms homolog from the so4357-so4362 operon was deleted in the single- dms gene mutants. This result revealed complementation of dmsEFABGH by so4357-so4362 at the single-gene level, indicating modularity of the extracellular electron transfer pathway encoded by dmsEFABGH operon. Under the conditions of all electron donors, significant inhibition of iodate reduction and accumulation of H 2 O 2 were detected for Δ mtrCAB . Collectively, these results demonstrated that the dmsEFABGH operon encodes an essential and modular iodate-reducing pathway without electron donor dependence in S. oneidensis MR-1. The mtrCAB operon was involved in H 2 O 2 elimination with all electron donors. The findings in this study improved the understanding of molecular mechanisms underlying extracellular iodate reduction.IMPORTANCEIodine is an essential trace element for human and animals. Recent studies revealed the contribution of microbial extracellular reduction of iodate in biogeochemical cycling of iodine. Multiple reduced substances can be utilized by microorganisms as energy source for iodate reduction. However, varied electron transfer pathways were proposed for iodate reduction with different electron donors in the model strain Shewanella oneidensis MR-1. Here, through a series of gene deletion and iodate reduction experiments, we discovered that the dmsEFABGH operon was essential for iodate reduction with at least three electron donors, including lactate, formate, and H 2 . The so4357-so4362 operon was first demonstrated to be capable of complementing the function of dmsEFABGH at single-gene level., Competing Interests: The authors declare no conflict of interest.

Iodine is an essential trace element in the human diet because it is involved in the synthesis of thyroid hormones. Iodine deficiency affects over 2.2 billion people worldwide, making it a significant challenge to find plant-based sources of iodine that meet the recommended daily intake of this trace element. In this study, cabbage plants were cultivated in a hydroponic system containing iodine at concentrations ranging from 0.01 to 1.0 mg/L in the form of potassium iodide or potassium iodate. During the experiments, plant physiological parameters, biomass production, and concentration changes of iodine and selected microelements in different plant parts were investigated. In addition, the oxidation state of the accumulated iodine in root samples was determined. Results showed that iodine addition had no effect on photosynthetic efficiency and chlorophyll content. Iodide treatment did not considerably stimulate biomass production but iodate treatment increased it at concentrations less than 0.5 mg/L. Increasing iodine concentrations in the nutrient solutions increased iodine content in all plant parts; however, the iodide treatment was 2-7 times more efficient than the iodate treatment. It was concluded, that iodide addition was more favourable on the target element accumulation, however, it should be highlighted that application of this chemical form in nutrient solution decreased the concetrations of selected micoelement concentration comparing with the control plants. It was established that iodate was reduced to iodide during its uptake in cabbage roots, which means that independently from the oxidation number of iodine (+ 5, - 1) applied in the nutrient solutions, the reduced form of target element was transported to the aerial and edible tissues., (© 2024. The Author(s).)

To investigate their roles in extracellular reduction of iodate (IO 3 - ) with lactate as an electron donor, the gene clusters of dmsEFAB, mtrCAB, mtrDEF and so4360-4357 in Shewanella oneidensis MR-1 were systematically deleted. Deletions of dmsEFAB and/or mtrCAB gene clusters diminished the bacterial ability to reduce IO 3 - . Furthermore, DmsEFAB and MtrCAB worked collaboratively to reduce IO 3 - of which DmsEFAB played a more dominant role than MtrCAB. MtrCAB was involved in detoxifying the reaction intermediate hydrogen peroxide (H 2 O 2 ). The reaction intermediate hypoiodous acid (HIO) was also found to inhibit microbial IO 3 - reduction. SO4360-4357 and MtrDEF, however, were not involved in IO 3 - reduction. Collectively, these results suggest a novel mechanism of extracellular reduction of IO 3 - at molecular level, in which DmsEFAB reduces IO 3 - to HIO and H 2 O 2 . The latter is further reduced to H 2 O by MtrCAB to facilitate the DmsEFAB-mediated IO 3 - reduction. The extracellular electron transfer pathway of S. oneidensis MR-1 is believed to mediate electron transfer from bacterial cytoplasmic membrane, across the cell envelope to the DmsEFAB and MtrCAB on the bacterial outer membrane., (© 2022 Society for Applied Microbiology and John Wiley & Sons Ltd.)

The removal of environmental pollutants is important for a sustainable ecosystem and human health. Shewanella oneidensis (S. oneidensis) has diverse electron transfer pathways and can use a variety of contaminants as electron acceptors or electron donors. This paper reviews S. oneidensis's function in removing environmental pollutants, including heavy metals, inorganic non-metallic ions (INMIs), and toxic organic pollutants. S. oneidensis can mineralize o-xylene (OX), phenanthrene (PHE), and pyridine (Py) as electron donors, and also reduce azo dyes, nitro aromatic compounds (NACs), heavy metals, and iodate by extracellular electron transfer (EET). For azo dyes, NACs, Cr(VI), nitrite, nitrate, thiosulfate, and sulfite that can cross the membrane, S. oneidensis transfers electrons to intracellular reductases to catalyze their reduction. However, most organic pollutants cannot be directly degraded by S. oneidensis, but S. oneidensis can remove these pollutants by self-synthesizing catalysts or photocatalysts, constructing bio-photocatalytic systems, driving Fenton reactions, forming microbial consortia, and genetic engineering. However, the industrial-scale application of S. oneidensis is insufficient. Future research on the metabolism of S. oneidensis and interfacial reactions with other materials needs to be deepened, and large-scale reactors should be developed that can be used for practical engineering applications., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

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 (IO 3 - ) as an electron acceptor by microorganisms is poorly understood. Here, we outline genetic, physiological, and ecological models for dissimilatory IO 3 - reduction to iodide (I - ) by a novel estuarine bacterium, Denitromonas sp. IR-12. Our results show that dissimilatory iodate reduction (DIR) by strain IR-12 is molybdenum-dependent and requires an IO 3 - 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, we propose a model where three molecules of IO 3 - are likely reduced to three molecules of hypoiodous acid (HIO), which rapidly disproportionate into one molecule of IO 3 - and two molecules of 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 (high concentrations of nitrate and phosphate) and diminished oxygen. Taken together, these data suggest that DIRM help explain the disequilibrium of the IO 3 - :I - concentration ratio above oxygen-minimum zones and support a widespread iodine redox cycle mediated by microbiology., (© 2021. The Author(s).)

Pseudomonas sp. strain SCT is capable of using iodate (IO 3 - ) as a terminal electron acceptor for anaerobic respiration. A possible key enzyme, periplasmic iodate reductase (Idr), was visualized by active staining on non-denaturing gel electrophoresis. Liquid chromatography-tandem mass spectrometry analysis revealed that at least four proteins, designated as IdrA, IdrB, IdrP 1 , and IdrP 2 , were involved in Idr. IdrA and IdrB were homologues of catalytic and electron transfer subunits of respiratory arsenite oxidase (Aio); however, IdrA defined a novel clade within the dimethylsulfoxide (DMSO) reductase family. IdrP 1 and IdrP 2 were closely related to each other and distantly related to cytochrome c peroxidase. The idr genes (idrABP 1 P 2 ) formed an operon-like structure, and their transcription was upregulated under iodate-respiring conditions. Comparative proteomic analysis also revealed that Idr proteins and high affinity terminal oxidases (Cbb 3 and Cyd), various H 2 O 2 scavengers, and chlorite (ClO 2 - ) dismutase-like proteins were expressed specifically or abundantly under iodate-respiring conditions. These results suggest that Idr is a respiratory iodate reductase, and that both O 2 and H 2 O 2 are formed as by-products of iodate respiration. We propose an electron transport chain model of strain SCT, in which iodate, H 2 O 2 , and O 2 are used as terminal electron acceptors., (© 2020 Society for Applied Microbiology and John Wiley & Sons Ltd.)

The use of iodine-biofortified vegetables may be a health alternative instead of iodine-biofortified salt for preventing iodine (I) deficiency and related human disorders. In this study, four Brassica genotypes (broccoli raab, curly kale, mizuna, red mustard) were hydroponically grown with three I-IO₃ - rates (0, 0.75 and 1.5 mg/L) to produce iodine-biofortified vegetables. Crop performances and quality traits were analyzed; iodine content was measured on raw, boiled, and steamed vegetables. The highest I rate generally increased I content in all Brassica genotypes, without plants toxicity effects in terms of reduced growth or morphological symptoms. After 21 day-iodine biofortification, the highest I content (49.5 µg/100 g Fresh Weight (FW)) was reached in broccoli raab shoots, while after 43 day-iodine biofortification, genotype differences were flattened and the highest I content (66 µg/100 g FW, on average) was obtained using 1.5 mg I-IO₃/L. Nitrate content (ranging from 1800 to 4575 mg/kg FW) was generally higher with 0.75 mg I-IO₃/L, although it depended on genotypes. Generally, boiling reduced iodine content, while steaming increased or left it unchanged, depending on genotypes. Applying low levels of I proved to be suitable, since it could contribute to the partial intake of the recommended dose of 150 µg/day: A serving size of 100 g may supply on average 24% of the recommended dose. Cooking method should be chosen in order to preserve and/or enhance the final I amount.

The metal-reducing gammaproteobacterium Shewanella oneidensis reduces iodate (IO 3 - ) as an anaerobic terminal electron acceptor. Microbial IO 3 - electron transport pathways are postulated to terminate with nitrate (NO 3 - ) reductase, which reduces IO 3 - as an alternative electron acceptor. Recent studies with S. oneidensis , however, have demonstrated that NO 3 - reductase is not involved in IO 3 - reduction. The main objective of the present study was to determine the metal reduction and protein secretion genes required for IO 3 - reduction by Shewanella oneidensis with lactate, formate, or H 2 as the electron donor. With all electron donors, the type I and type V protein secretion mutants retained wild-type IO 3 - reduction activity, while the type II protein secretion mutant lacking the outer membrane secretin GspD was impaired in IO 3 - reduction. Deletion mutants lacking the cyclic AMP receptor protein (CRP), cytochrome maturation permease CcmB, and inner membrane-tethered c -type cytochrome CymA were impaired in IO 3 - reduction with all electron donors, while deletion mutants lacking c -type cytochrome MtrA and outer membrane β-barrel protein MtrB of the outer membrane MtrAB module were impaired in IO 3 - reduction with only lactate as an electron donor. With all electron donors, mutants lacking the c -type cytochromes OmcA and MtrC of the metal-reducing extracellular electron conduit MtrCAB retained wild-type IO 3 - reduction activity. These findings indicate that IO 3 - reduction by S. oneidensis involves electron donor-dependent metal reduction and protein secretion pathway components, including the outer membrane MtrAB module and type II protein secretion of an unidentified IO 3 - reductase to the S. oneidensis outer membrane. IMPORTANCE Microbial iodate (IO 3 - ) reduction is a major component in the biogeochemical cycling of iodine and the bioremediation of iodine-contaminated environments; however, the molecular mechanism of microbial IO 3 - reduction is poorly understood. Results of the present study indicate that outer membrane (type II) protein secretion and metal reduction genes encoding the outer membrane MtrAB module of the extracellular electron conduit MtrCAB are required for IO 3 - reduction by S. oneidensis On the other hand, the metal-reducing c -type cytochrome MtrC of the extracellular electron conduit is not required for IO 3 - reduction by S. oneidensis These findings indicate that the IO 3 - electron transport pathway terminates with an as yet unidentified IO 3 - reductase that associates with the outer membrane MtrAB module to deliver electrons extracellularly to IO 3 ., (Copyright © 2019 American Society for Microbiology.)

Nitrate and radioiodine ( 129 I) contamination is widespread in groundwater underneath the Central Plateau of the Hanford Site. 129 I, a byproduct of nuclear fission, is of concern due to a 15.7 million year half-life, and toxicity. The Hanford 200 West Area contains plumes covering 4.3 km 2 with average 129 I concentrations of 3.5 pCi/L. Iodate accounts for 70.6% of the iodine present and organo-iodine and iodide make up 25.8% and 3.6%, respectively. Nitrate plumes encompassing the 129 I plumes have a surface area of 16 km 2 averaging 130 mg/L. A nitrate and iodate reducing bacterium closely related to Agrobacterium, strain DVZ35, was isolated from sediment incubated in a 129 I plume. Iodate removal efficiency was 36.3% in transition cultures, and 47.8% in anaerobic cultures. Nitrate (10 mM) was also reduced in the microcosm. When nitrate was spiked into the microcosms, iodate removal efficiency was 84.0% and 69.2% in transition and anaerobic cultures, respectively. Iodate reduction was lacking when nitrate was absent from the growth medium. These data indicate there is simultaneous reduction of nitrate and iodate by DVZ35, and iodate is reduced to iodide. Results provide the scientific basis for combined nitrogen and iodine cycling throughout the Hanford Site., (Copyright © 2018. Published by Elsevier B.V.)

Background: Iodine deficiency is an environmental health problem affecting one-third of the global population. An iodine biofortification hydroponic experiment was conducted to explore the iodide and iodate uptake characteristics of strawberry plants, to measure the dosage effects of iodine on plant growth and to evaluate the influence of I - or IO 3 - application on fruit quality., Results: After biofortification, the iodine contents of the fresh strawberry fruits were 600-4000 µg kg -1 , covering the WHO dietary iodine allowance of 150 µg · day -1 for adults. The iodine uptake of the strawberry plants increased with increasing I - or IO 3 - concentration of the culture solution. At the same iodine concentration, the iodate uptakes of various plant organs under I - treatments were apparently more than those under IO 3 - treatments. Low-level exogenous iodine (I - ≤ 0.25 mg L -1 or IO 3 - ≤ 0.50 mg L -1 ) not only promoted plant growth and increased biomass per plant, but also improved fruit quality by enhancing the vitamin C and soluble sugar contents of the strawberry fruits. Nevertheless, excessive exogenous iodine inhibited plant growth and reduced biomass per plant. IO 3 - uptake apparently increased the total acidity and nitrate content of the fruits, reducing the quality of the strawberry fruits. Conversely, I - uptake obviously decreased the total acidity and nitrate content of the strawberry fruits, improving the fruit quality., Conclusion: The strawberry can be used as a target crop for iodine biofortification. Furthermore, applying an appropriate dose of KI can improve the fruit quality of the strawberry plants. © 2016 Society of Chemical Industry., (© 2016 Society of Chemical Industry.)

Iodine is a biophilic element that is important for human health, both as an essential component of several thyroid hormones and, on the other hand, as a potential carcinogen in the form of radioiodine generated by anthropogenic nuclear activity. Iodine exists in multiple oxidation states (-1, 0, +1, +3, +5, and +7), primarily as molecular iodine (I 2 ), iodide (I - ), iodate [Formula: see text] , or organic iodine (org-I). The mobility of iodine in the environment is dependent on its speciation and a series of redox, complexation, sorption, precipitation, and microbial reactions. Over the last 15years, there have been significant advances in iodine biogeochemistry, largely spurred by renewed interest in the fate of radioiodine in the environment. We review the biogeochemistry of iodine, with particular emphasis on the microbial processes responsible for volatilization, accumulation, oxidation, and reduction of iodine, as well as the exciting technological potential of these fascinating microorganisms and enzymes., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Purpose: To establish the dose of subretinal sodium iodate (NaIO3) in order to create a toxin-induced large animal model of selective circumscribed atrophy of outer retinal layers, the retinal pigment epithelium (RPE), and photoreceptors, by spectral-domain optical coherence tomography (SD-OCT) and immunocytochemistry., Methods: Fifteen male and female healthy Yorkshire pigs received unilateral subretinal escalating doses of NaIO3 under general anesthesia. In all the animals, volumes of 0.1 to 0.2 mL NaIO3 were injected into the subretinal space of the area centralis through a 23/38-gauge subretinal cannula. Control SD-OCTs were performed 1 and 2 months after the surgery, at which time pigs were euthanized and eyes enucleated. Globes were routinely processed for histologic and immunohistochemical evaluation., Results: Spectral-domain OCT and immunohistochemistry revealed circumscribed and well-demarcated funduscopic lesions, limited to the outer retinal layers in pigs treated with 0.01 mg/mL subretinal sodium iodate., Conclusions: The swine model of a controlled area of circumscribed retinal damage, with well-delimited borders, and selectively of the outer layers of the retina presented herein shows several clinical and histologic features of geographic atrophy in AMD. Therefore, it may represent a valuable tool in the investigation of new emerging regenerative therapies that aim to restore visual function, such as stem cell transplantation or optogenetics.

Herein, we report a novel third-generation H2O2 and IO3- biosensor, which was fabricated by loading catalase (CAT) onto l-lysine/multiwalled carbon nanotube (PLL/f-MWCNT) film modified glassy carbon electrode (GCE). The UV-visible (UV-vis) and Fourier-transform infrared (FTIR) spectra show that the catalase encapsulated in the PLL/f-MWCNT film can effectively retain its bioactivity. The immobilized CAT retained its bioactivity with a high protein loading of 4.072 × 10(-10) mol cm(-2), thus exhibiting a surface-controlled reversible redox reaction, with a fast heterogeneous electron transfer rate of 5.48 s(-1). The immobilized CAT shows a couple of reversible and well-defined cyclic voltammetry peaks with a formal potential (E(0)) of -0.471 V (vs. Ag/AgCl) in a pH 6.5 phosphate buffer solution (PBS). Moreover, the modified film exhibited high electrocatalytic activity for the reduction of hydrogen peroxide (H2O2). It exhibited a wide linear response to H2O2 in the concentration range of 1 × 10(-6) - 3.6 × 10(-3), with higher sensitivity (392 mA cm(-2) M(-1)) and a lower Michaelis-Menten constant (0.224 mM). It provided high-catalytic activity towards H2O2 in a shorter time (5s), with a detection limit of 8 nM. These results indicate great improvement in the electrochemical and electrocatalytic properties of the CAT/PLL/f-MWCNT biosensor, offering a new idea for the design of third-generation electrochemical biosensors., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Young hens were fed over a period of 150 d with 2 kinds of diets including corn and soybean meal or corn, soybean, and rapeseed meal. Diets were enriched with potassium iodide (KI) or potassium iodate (KIO3) as an I source in amounts equal to 1, 3, or 5 mg of supplemented I/kg of feed. The hen performance, egg quality, hematological and morphotic indices in blood, hepatic enzyme activity, lipid indices in blood serum as well as I accumulation in wet egg content were determined. Introduction of 00-variety rapeseed meal into the diet improved the laying rate and feed conversion (P < 0.05); however, better egg weight was noted by feeding the hens with a diet without rapeseed meal. Use of KI as an I source enhanced the egg weight. The increased I level in the diet had an equivocal influence on egg weight, improved the feed conversion per 1 kg of eggs, and decreased the proportion of damaged eggs. The use of corn, soybean, and rapeseed meal in hen diets significantly improved yolk color; similar results were noted after an increase in I levels in the diets after 3 mo of feeding. Hematological indices of hen blood demonstrated significantly higher red blood cells numbers and hemoglobin concentrations with the use of KI. The use of a diet containing rapeseed meal led to an enhancement of hepatic enzyme activity, especially of alkaline phosphatase (P = 0.007). Lipid metabolism indices were not influenced by the kind of diet or the I source or level. The accumulation of I in wet egg content was negatively influenced by the use of a diet containing rapeseed meal (P = 0.000). The application of KI as an I source enhanced (P = 0.003) the accretion of I in eggs after 5 mo of treatment. Enhanced I supply significantly increased accumulation of I in eggs (P = 0.000) after 3 and 5 mo of the experiment from 260 and 310 to 1,011 and 1,256 µg/kg of wet egg content, respectively., (©2014 Poultry Science Association Inc.)

Iodine, applied as iodate in biofortification programs (at doses of ≤80 μM), has been confirmed to improve the foliar biomass, antioxidant response, and accumulation of phenol compounds in lettuce plants. The changes in phenolic compounds induced by the iodate application appear to have functional consequences in the response of salt-stressed plants. Thus, the aim of the present study was to determine whether the application of iodate can improve the response of severe salinity stress and whether the resistance can be attributed to the phenolic metabolism in lettuce ( Lactuca sativa cv. Philipus), a glycophyte cultivated for food and consumed year round. In this work, the application of iodate, especially at 20 and 40 μM, in lettuce plants under salinity stress (100 mM NaCl) exerted a significantly positive effect on biomass and induced higher activity in the enzymes shikimate dehydrogenase and phenylalanine ammonia-lyase as well as the lower MW phenol-degrading enzyme polyphenol oxidase. This increased hydroxycinnamic acids and derivatives in addition to total phenols, which appear to act as protective compounds against salinity. This study reveals that in agricultural areas affected by this type of stress, the application of iodate may be an effective strategy, as it not only improves lettuce plant growth but also supplements the human diet with phenolic compounds and the trace element iodine.

In the presented study the effect of different iodine (I) levels and sources in hen feed on the iodine concentration of different tissues, blood serum, and eggs of laying hens was studied. For this purpose, two experiments were conducted with 30 laying hens each. In these experiments feed was enriched with KI and Ca(IO(3))(2), respectively, at 0 (Control), 0.25, 0.5, 2.5 and 5 mg I/kg feed, resulting a analysed iodine level from 0.44 to 4.20 mg/kg feed. After four weeks experimental feeding the iodine concentrations of thyroid glands, blood, meat, liver, abdominal fat and eggs were measured with inductively coupled plasma mass spectrometry. The experimental treatment did not affect hen performance. The iodine supplementation significantly increased the iodine concentration of eggs (144-1304 μg/kg), thyroid glands (3367-5975 μg/g), blood serum (16-67 μg/kg) and liver (13-43 μg/kg). Meat (about 14 μg I/kg) and abdominal fat (about 12 μg I/kg) were not significantly affected by iodine treatment. Comparative regression analyses showed that at a similar iodine intake, the supply via KI resulted in significantly higher iodine deposition into eggs than Ca(IO(3))(2). Due to the high carry-over of iodine into eggs, eggs may considerably contribute to the iodine supply of the consumers.

Adsorption-desorption of iodine in two forms, viz., iodide (I(-)) and iodate (IO (3) (-) ), in three types of soil were investigated. The soils were: red soil developed on Quaternary red earths (REQ)- clayey, kaolintic thermic plinthite Aquult, Inceptisol soil (IS) and alluvial soil (AS)-Fluvio-marine yellow loamy soil. The isothermal curves of iodine adsorption on soils were described by Langmuir and Freundlich equation, and the maximum adsorption values (y (m)) were obtained from the simple Langmuir model. As compared with the iodide, the iodate was adsorbed in higher amounts by the soils tested. Among three soils, the REQ soil adsorbed more iodine (I(-) and IO (3) (-) ) than the IS and AS. The distribution coefficient (K (d)) of iodine in the soils decreased exponentially with increasing iodine loading concentration. Desorption of iodine in soil was increased correspondingly with increasing adsorption values. The REQ soil had a greater affinity for iodine than the IS and AS at the same iodine loadings. In the pot experiment cultivated with pakchoi (Brassica chinensis L.) and added with two exogenous iodine sources, the iodide form was quickly taken up by pakchoi and caused more toxicity to the vegetable. The rate of iodine loss from soil was higher for iodide form as compared with the iodate. The iodine bioavailability was the highest but the persistence was the weakest in AS among the three soils tested, and the REQ soil showed just the opposite trend to that of the AS soil. This study is of theoretical importance to understand the relationship between iodine adsorption-desorption characteristics and their bioavailability in different soils and it also has practical implications for seeking effective alternatives of iodine biofortification to prevent iodine deficiency disorders.

Background: Universal salt iodization promotes the use of iodated salt for producing industrial food products, although it might affect product quality and iodine stability., Objective: To assess iodine loss during fermentation of fermented fish and fish sauces produced by using iodated salt and the effect on product sensory quality., Methods: Fermented fish and fish sauces were produced with iodated rock and grain sea salts (approximately 30 ppm iodine). Fermented fish was prepared from freshwater fish mixed with salt and rice bran and fermented for 6 months at room temperature. Fish sauces were prepared by mixing anchovy with salt and fermenting either exposed to sunlight or in the shade for 12 months. Residual iodine was determined with a spectrophotometer at day 0 and months 1, 3, and 6 for fermented fish and day 0 and months 3, 6, and 12 for fish sauces. After fermentation, the products were tested for sensory acceptability by Laotian and Thai panelists (approximately 50 in each panel) after they were cooked and served in the traditional manner., Results: After fermentation, the level of residual iodine was 7.61 ppm (16% loss) infermented fish, 5.57 ppm (55% loss) in fish sauce prepared with exposure to sunlight, and 9.52 ppm (13% loss) in fish sauce prepared in the shade. Sensory qualities of the products that were produced from fortified and unfortified salts as well as dishes prepared from these products were not significantly different (p > 0.05)., Conclusions: It is feasible to produce fermented fish and fish sauces with iodated salt and maintain acceptable iodine levels.

The essentiality of iodine for humans, especially in the early stages of life, is well recognized. The chemical forms of iodine in food supplements, infant formulae and iodated salt are either iodide (KI) or iodate (KIO(3)). Because there are no or rare data about iodine uptake by yeasts, we investigated the influence of different sources of iodine, as KI, KIO(3) and periodate (KIO(4)), on its uptake in and growth of the model yeast Saccharomyces cerevisiae. KIO(3) inhibited the growth of the yeast the most and already at a 400 microM initial concentration in the growth medium; the OD was reduced by 23% in comparison with the control, where no KIO(3) was added. The uptake of different iodine sources by the yeast S. cerevisiae was minimal, in total <1%. Tracer experiments with radioactive (131)I added as KI showed that the yeast S. cerevisiae does not have the ability to transform KI into volatile species. We investigated the specificity of iodine uptake added as KIO(3) in the presence of Na(2)SeO(4) or ZnCl(2) or K(2)CrO(4) in the growth medium, and it was found that chromate had the most influence on reduction of KIO(3) uptake.

Objective: Iodine deficiency disorders continue to be a severe problem in many parts of Central Asia, causing delayed mental development and cretinism in indigenous populations. In some areas, iodized salt has not succeeded in controlling this problem. In southern Xinjiang Province of China, we tried a new method of supplying iodine to rural populations by dripping potassium iodate into irrigation water canals. By this means iodine was distributed into soil, crops, animals and people. This proved feasible and cost effective; it reached all the people, required no medical expertise, required no continuing effort after the initial dripping, and had the important added benefit of improving livestock production., Methods: We serially monitored iodine concentrations in soil, crops, animal products and human urine for several years after the last dripping. In a similar project in Inner Mongolia, total soil iodine was determined in addition. Here, iodine concentrations in soil, crops, animals and people have been monitored for 4 years after supplementation., Results: After dripping, total iodine increased two-fold, while soluble iodine increased 4-5-fold. Iodine added to soil is available for more than 4 years after a single application., Conclusions: Potassium iodate added to soil appears to increase soluble iodine out of proportion to the amount added. This effect and the long persistence of dripped iodate in soil contribute to the efficacy and cost effectiveness of this method of iodine supplementation.

Bacterial iodate (IO(3)(-)) reduction is poorly understood largely due to the limited number of available isolates as well as the paucity of information about key enzymes involved in the reaction. In this study, an iodate-reducing bacterium, designated strain SCT, was newly isolated from marine sediment slurry. SCT is phylogenetically closely related to the denitrifying bacterium Pseudomonas stutzeri and reduced 200 microM iodate to iodide (I(-)) within 12 h in an anaerobic culture containing 10 mM nitrate. The strain did not reduce iodate under the aerobic conditions. An anaerobic washed cell suspension of SCT reduced iodate when the cells were pregrown anaerobically with 10 mM nitrate and 200 microM iodate. However, cells pregrown without iodate did not reduce it. The cells in the former category showed methyl viologen-dependent iodate reductase activity (0.31 U mg(-1)), which was located predominantly in the periplasmic space. Furthermore, SCT was capable of anaerobic growth with 3 mM iodate as the sole electron acceptor, and the cells showed enhanced activity with respect to iodate reductase (2.46 U mg(-1)). These results suggest that SCT is a dissimilatory iodate-reducing bacterium and that its iodate reductase is induced by iodate under anaerobic growth conditions.

A simple, precise, sensitive and accurate method was developed for rapid determination of trace quantities of iodate. The method is based on the accelerating effect of iodate on the reaction of bromate and chloride acid in the presence of hydrazine in acidic media. The decolorization of Methyl Orange with the reaction products was used to monitor the reaction spectrophotometrically at 525 nm. Iodate could be determined in the concentration ranges of 0.03 - 1.2 microg ml(-1). The relative standard deviation for ten replicate determinations of 0.3 microg ml(-1) of iodate was 1.65%. The proposed method was applied to the determination of iodate in table salts with satisfactory results.

Hotien prefecture, Xinjiang Province, China, in the Taklamakan Desert, is an area of severe iodine deficiency. Because usual methods of iodine supplementation failed here, we began supplementation in 1992 with potassium iodate, which was added to irrigation water (Lancet 1994; 334:107-110). We report 4 y experience with this method in 3 townships that contained a total treated population of 37,000. Potassium iodate was dripped into irrigation water (to a concentration 10-80 microg/l) during a 2- to 4-wk period. During the 3 y that followed, no further supplementation was made, and iodine concentrations increased several fold in crops and plants, sheep and chicken thyroid glands, and meat and in urine of children 2-6 y of age and of women who were of childbearing age. Infant mortality decreased 50%, and sheep production increased 43%. Iodine repletion of soil through irrigation water is an effective and cost-efficient way of providing iodine in appropriate situations.

Methanol is an ocular toxicant which causes visual dysfunction often leading to blindness after acute exposure. The physiological and biochemical changes responsible for this toxicity are poorly understood. Previously, we reported that the folate-reduced (FR) rat is an animal model which mimics the characteristic human methanol toxicities. The present study examines the hypothesis that depletion of ATP after methanol administration is the initiating event in methanol-induced retinal toxicity. ATP is reduced in retinae of methanol-treated FR rats to the same extent as is seen in retinae of FR and folate-sufficient (FS) rats treated with the Müller cell (retinal glial cell) toxin alpha-aminoadipic acid. Changes in the electroretinogram and the response of Müller cells to a potassium stimulus are also similarly eliminated in methanol-treated FR rats and alpha-aminoadipic acid-treated FR and FS rats. These results suggest that the Müller cell may be the initial target in methanol-induced visual system toxicity.

Vanadate (VO3-) was found to activate adenylyl cyclase (AC) in ocular ciliary process membrane. This response was additive to that of isoproterenol (ISO) and vasoactive intestinal peptide (VIP), but it was potentiative with forskolin (FSK) and also with Ca2+/calmodulin activation of AC activity. The potentiated response of FSK in the presence of VO3- was due to an increase in Vmax without a change in the apparent affinity of FSK or VO3-, and therefore differs from the potentiated response of activated G-protein (Gs) and FSK, where the affinity of FSK was increased by 1-2 orders of magnitude. Potentiation occurred at low Mg2+ and was not observed at free [Mg2+] > 3 mM. Iodate (IO3-) inhibited the FSK, ISO, and VO3- activations of AC in ciliary process membranes (IC50, 0.3 mM). In vivo topical treatment of the rabbit eye with 50 microL of 5% NaIO3 had no effect alone but completely blocked the intraocular pressure response to a 50-microL topical dose of 1% FSK and partially blocked the response to a 50-microL dose of 0.001% ISO. These findings indicate that some AC enzymes may have a binding site for oxyanions which can directly regulate enzyme activity.

The crystal structure of the complex formed between phospholipase C (PLC) from Bacillus cereus and inorganic phosphate (Pi), which is an inhibitor, has been determined and refined to 2.1 A resolution. The final R-factor is 19.7%. We have also studied the binding of two other inhibitors, iodide and iodate, to PLC. X-ray data for these two complexes were collected to 2.8 A resolution during the search for heavy-atom derivatives. A series of screening experiments where PLC crystals have been treated with several reaction products and a substrate analogue were carried out to clarify the question of substrate binding. The results have so far been ambiguous but are discussed briefly. Phosphate and iodate are both found to bind to the three metal ions in the protein molecule, suggesting that these ions are involved directly in the catalytic process and thereby identifying the active site. PLC also binds nine iodide ions, eight of which are on the surface of the molecule and of lower occupancy. The ninth blocks the entrance to the active site cleft and is of higher occupancy. Altogether, these results suggest that the substrate, a phospholipid, is associated directly with the metal ions during catalysis.

Chemical forms of radioactive iodine and its effects upon marine organisms were studied by the tracer experiments. Seaweeds or fish were held in the aquarium in which the 125I tracer in either iodide or iodate form was inoculated. Iodide form of 125I was taken by Dorome (Chasmichthys gulosus) with the concentration factor of about 10 and excreted with the biological half-life of 15 days, while iodate form of 125I was not taken up appreciably and the concentration factor did not greatly exceed unity. Uptake and loss of 125I were studied as well for 3 species of seaweeds, Hijiki(Hizikia fusiforme), Nejimoku (Sargassum sagamianum) and Tsunomata (Chondrus ocellatus). Iodate form of 125I was accumulated less than iodide form by these seaweeds but the concentration factor of iodate by these seaweeds was very high compared to those by fish.

The inhibitory effect of ascorbic acid on commercial test strip reactions for haematuria is demonstrated in vitro. A new test strip containing iodate is shown to be insensitive to even high ascorbic acid concentrations in the same in vitro experiments.

Accumulation of iodate in eye tissues and fluids as a possible explanation of the retinotoxic effect of iodate has been studied by intravenous injection of NaIO3(30 mg/kg), 125IO-3 and 131I- in rabbits. 125IO-3 was determined in fluids and tissue extracts by precipitation with BaCl2 after addition of KIO3. 125IO-3 was rapidly broken down in blood (T 1/2 = 14 min.). 125IO-3 was not present in aqueous humour, vitreous or extracts from retina, choroid + pigmentary epithelium or liver. Concentrations of 125I were comparable in blood, choroid + pigmentary epithelium and liver tissue while in vitreous and aqueous humour low concentrations of 125I were found which, however, increased gradually during 5 hrs after injection to reach levels comparable with blood levels of 125I. Retina had a low concentration of 125I. The ratio 125I/131I (R) in blood decreases during the first 60 min. after injection followed by a slow rise. R in retina, choroid + pigmentary epithelium and liver was the same as in blood at the same time after injection. During the first 80 min. after injection R was higher in vitreous than in blood while it was lower in aqueous humour than in blood. At longer times after injection R was identical in the three fluids. The investigation has been supplemented with whole body scintigraphy of rabbits injected with NaIO3(30 mg/kg) and 131IO-3 or 131I-. The reduction kinetics of IO-3 to I- by some body fluids, tissues, cystein and glutathione was also studied. It is concluded that the retinotoxic effect of iodate is not due to accumulation of IO-3 in eye tissues, but more likely to damage to biochemical mechanisms involved in the reduction of IO-3 to I-.