Shifting the Specificity of E. coli Biosensor from Inorganic Arsenic to Phenylarsine Oxide through Genetic Engineering

It has recently been discovered that organic and inorganic arsenics could be detrimental to human health. Although organic arsenic is less toxic than inorganic arsenic, it could form inorganic arsenic through chemical and biological processes in environmental systems. In this regard, the availability of tools for detecting organic arsenic species would be beneficial. Because As-sensing biosensors employing arsenic responsive genetic systems are regulated by ArsR which detects arsenics, the target selectivity of biosensors could be obtained by modulating the selectivity of ArsR. In this study, we demonstrated a shift in the specificity of E. coli cell-based biosensors from the detection of inorganic arsenic to that of organic arsenic, specifically phenylarsine oxide (PAO), through the genetic engineering of ArsR. By modulating the number and location of cysteines forming coordinate covalent bonds with arsenic species, an E. coli cell-based biosensor that was specific to PAO was obtained. Despite its restriction to PAO at the moment, it offers invaluable evidence of the potential to generate new biosensors for sensing organic arsenic species through the genetic engineering of ArsR.

Drinking Water Arsenic Contamination, Skin Lesions, and Malignancies: A Systematic Review of the Global Evidence

Skin lesions and cancer are known manifestations of chronic exposure to arsenic contaminated drinking water. Epidemiologic data primarily comes from regions with exposures 1-2 orders of magnitude above the current World Health Organization (WHO) guidelines of 10 μg/L. Emerging evidence indicates that more common exposures may also be related to both noncancerous and cancerous changes to the skin. In this review, we focus on the body of epidemiologic literature that encompasses exposures within the WHO guidelines, excluding studies that lacked individual exposure estimates and case reports. For skin lesions and skin cancers, 15 and 10 studies were identified that met our criteria, respectively. For skin lesions, a consistent dose-response relationship with water arsenic has been observed, with increased risk evident at low- to moderate-dose exposure. Of the larger studies of specific histologic types of skin cancers, although with differing exposure definitions, there was evidence of dose-related relationships with both basal cell carcinomas and squamous cell carcinomas. The effect of arsenic exposure on skin lesion risk is likely modified by genetic variants that influence arsenic metabolism. Accumulating evidence suggests that arsenic may increase risk of skin lesions and skin cancers at levels not previously considered harmful, and that genetic factors may influence risk.

Arsenic: bioaccessibility from seaweed and rice, dietary exposure calculations and risk assessment

Arsenic is a metalloid that occurs in food and the environment in different chemical forms. Inorganic arsenic is classified as a class I carcinogen. The inorganic arsenic intake from food and drinking water varies depending on the geographic arsenic background. Non-dietary exposure to arsenic is likely to be of minor importance for the general population within the European Union. In Europe, arsenic in drinking water is on average low, but food products (e.g. rice and seaweed) are imported from all over the world including from regions with naturally high arsenic levels. Therefore, specific populations living in Europe could also have a high exposure to inorganic arsenic due to their consumption pattern. Current risk assessment is based on exposure via drinking water. For a good estimation of the risks of arsenic in food, it is important to investigate if the bioavailability of inorganic arsenic from food is different from drinking water. The present study further explores the issue of European dietary exposure to inorganic arsenic via rice and seaweed and its associated health risks. The bioavailability of inorganic arsenic was measured in in vitro digestion experiments. The data indicate that the bioavailability of inorganic arsenic is similar for rice and seaweed compared with drinking water. The calculated dietary intake for specific European Union populations varied between 0.44 and 4.51 µg kg⁻¹ bw day⁻¹. The margins of exposure between the inorganic intake levels and the BMDL0.5 values as derived by JECFA are low. Decreasing the intake of inorganic arsenic via Hijiki seaweed could be achieved by setting legal limits similar to those set for rice by the Codex Alimentarius Commission in July 2014.