Blood Pressure Associated with Arsenic Methylation and Arsenic Metabolism Caused by Chronic Exposure to Arsenic in Tube Well Water

Objective The effects of arsenic exposure from drinking water, arsenic metabolism, and arsenic methylation on blood pressure（BP） were observed in this study. Methods The BP and arsenic species of 560 participants were determined. Logistic regression analysis was applied to estimate the odds ratios of BP associated with arsenic metabolites and arsenic methylation capability. Results BP was positively associated with cumulative arsenic exposure（CAE）. Subjects with abnormal diastolic blood pressure（DBP）, systolic blood pressure（SBP）, and pulse pressure（PP） usually had higher urinary i As（inorganic arsenic）, MMA（monomethylated arsenic）, DMA（dimethylated arsenic）, and TAs（total arsenic） than subjects with normal DBP, SBP, and PP. The i As%, MMA%, and DMA% differed slightly between subjects with abnormal BP and those with normal BP. The PMI and SMI were slightly higher in subjects with abnormal PP than in those with normal PP. Conclusion Our findings suggest that higher CAE may elevate BP. Males may have a higher risk of abnormal DBP, whereas females have a higher risk of abnormal SBP and PP. Higher urinary i As may increase the risk of abnormal BP. Lower PMI may elevate the BP. However, higher SMI may increase the DBP and SBP, and lower SMI may elevate the PP.

Evaluation of water management on arsenic methylation and volatilization in arsenic-contaminated soils strengthened by bioaugmentation and biostimulation

Arsenic(As) fate in paddy fields has been one of the most significant current issues due to the strong As accumulation potential of rice plants under fooded conditions. However,no attempt was done to explore As methylation and volatilization under non-fooded conditions. Herein, we investigated the effects of water management on As methylation and volatilization in three arsenic-contaminated soils enhanced by biostimulation with strawderived organic matter and bioaugmentation with genetic engineered Pseudomonas putida KT2440(GE P. putida). Under fooded conditions, the application of biochar(BC), rice straw(RS)and their combination(BC+RS) increased total As in porewater. However, these effects were greatly attenuated under non-fooded conditions. Compared with RS amendment alone, the combination of GE P. putida and RS further promoted the As methylation and volatilization,and the promotion percentage under non-fooded conditions were significantly higher than that under fooded conditions. The combined GE P. putida and RS showed the highest efficiency in As methylation(88 μg/L) and volatilization(415.4 μg/(kg·year)) in the non-fooded soil with moderate As contamination. Finally, stepwise multiple linear regression analysis presented that methylated As, DOC and p H in porewater were the most important factors contributing to As volatilization. Overall, our findings suggest that combination of bioaugmentation with GE P. putida and biostimulation with RS/BC+RS is a potential strategy for bioremediation of arsenic-contaminated soils by enhancing As methylation and volatilization under non-fooded conditions.

Arsenic methylation by an arsenite S-adenosylmethionine methyltransferase from Spirulina platensis

Arsenic-contaminated water is a serious hazard for human health. Plankton plays a critical role in the fate and toxicity of arsenic in water by accumulation and biotransformation.Spirulina platensis（S. platensis）, a typical plankton, is often used as a supplement or feed for pharmacy and aquiculture, and may introduce arsenic into the food chain, resulting in a risk to human health. However, there are few studies about how S. platensis biotransforms arsenic. In this study, we investigated arsenic biotransformation by S. platensis. When exposed to arsenite（As（Ⅲ））, S. platensis accumulated arsenic up to 4.1 mg/kg dry weight.After exposure to As（Ⅲ）, arsenate（As（Ⅴ）） was the predominant species making up 64% to86% of the total arsenic. Monomethylarsenate（MMA（Ⅴ）） and dimethylarsenate（DMA（Ⅴ））were also detected. An arsenite S-adenosylmethionine methyltransferase from S. platensis（Sp Ars M） was identified and characterized. Sp Ars M showed low identity with other reported Ars M enzymes. The Escherichia coli AW3110 bearing Spars M gene resulted in As（Ⅲ） methylation and conferring resistance to As（Ⅲ）. The in vitro assay showed that Sp Ars M exhibited As（Ⅲ） methylation activity. DMA（Ⅴ） and a small amount of MMA（Ⅴ） were detected in the reaction system within 0.5 hr. A truncated Sp Ars M derivative lacking the last 34 residues still had the ability to methylate As（Ⅲ）. The three single mutants of Sp Ars M（C59S, C186 S, and C238S） abolished the capability of As（Ⅲ） methylation, suggesting the three cysteine residues are involved in catalysis. We propose that Sp Ars M is responsible for As methylation and detoxification of As（Ⅲ） and may contribute to As biogeochemistry.

A review on completing arsenic biogeochemical cycle: Microbial volatilization of arsines in environment

Arsenic （As） is ubiquitous in the environment in the carcinogenic inorganic forms, posing risks to human health in many parts of the world. Many microorganisms have evolved a series of mechanisms to cope with inorganic arsenic in their growth media such as transforming As compounds into volatile derivatives. Bio-volatilization of As has been suggested to play an important role in global As biogeochemical cycling, and can also be explored as a potential method for arsenic bioremediation. This review aims to provide an overview of the quality and quantity of As volatilization by fungi, bacteria, microalga and protozoans. Arsenic bio-volatilization is influenced by both biotic and abiotic factors that can be manipulated/elucidated for the purpose of As bioremediation. Since As bio- volatilization is a resurgent topic for both biogeochemistry and environmental health, our review serves as a concept paper for future research directions.