Biotransformation Of Arsenate Research Articles

Role of microbial microbes in arsenic bioaccumulation and biotransformation in mice

Although gut microbes can affect the accumulation and metabolism of arsenic (As), the microbes contributing to these processes remain largely unknown. Therefore, this study aimed to investigate the bioaccumulation and biotransformation of arsenate [As(V)] and arsenobetaine (AsB) in mice with a disordered gut microbiome. We used cefoperazone (Cef) to construct a mouse model of gut microbiome disruption along with 16S rRNA sequencing to elucidate the effect of gut microbiome destruction on the biotransformation and bioaccumulation of As(V) and AsB. This revealed the role of specific bacteria in As metabolism. Gut microbiome destruction increased the bioaccumulation of As(V) and AsB in various organs and reduced the excretion of As(V) and AsB in the feces. Further, gut microbiome destruction was found to be important for the biotransformation of As(V). Interference with Cef can significantly decrease Blautia and Lactobacillus while increasing Enterococcus, leading to increase As accumulation in mice and enhanced methylation. We also identified Lachnoclostridium, Erysipelatoclostridium, Blautia, Lactobacillus, and Enterococcus as biomarkers involved in As bioaccumulation and biotransformation. In conclusion, specific microbes can increase As accumulation in the host, exacerbating its potential health risks.

Freshwater phytoplankton: Salinity stress on arsenic biotransformation.

Salinity stress affects aquatic microalgal growth and their physiological responses have been studied extensively. However, arsenic (As) accumulation and biotransformation by freshwater phytoplankton under a salinity gradient have never been addressed. This study reports a distinctive pattern of As uptake, accumulation, and biotransformation by four axenic freshwater phytoplankton species, i.e., Scenedesmus acutus, Closterium aciculare, Staurastrum paradoxum, and Pediastrum duplex. Phytoplankton cells were incubated in sterilised C medium modified with varying salinity levels (0-5‰) in association with arsenate and phosphate concentrations. The biotransformation of arsenate (i.e., As(V)) to arsenite (As(III)) and to further methylated species decreased with increasing salinity in the culture medium whereas As accumulation increased. Among the four strains, only S.acutus and S.paradoxum converted As(V) to As(III), with no detected methylated species. In contrast, C.aciculare and P.duplex biotransformed As(V) to As(III) and further to methyl arsenic species, such as DMAA. S.acutus and S.paradoxum exhibited higher accumulation tendency than the other two species. S.paradoxum showed the lowest As reduction rate (i.e., As(V) to As(III)) compared to other species, although, without significant variations. The morphological changes were observed in phytoplankton cells in response to increased salinity stress. Moreover, As(V) concentrations in the culture medium significantly decreased by day 7-14. Thus, this study presents a conceptual model of the As biotransformation pattern by axenic freshwater phytoplankton.

Accumulation and Biotransformation in Typical Freshwater Algae Species Influenced by Titanium Dioxide Nanoparticles Under Long-term Exposure

In the present study, the accumulation and biotransformation of arsenate in typical freshwater algae species were examined under long-term influence of titanium dioxide nanoparticles (nano-TiO2). Results showed that different algae species had largely varied capacities of accumulation and biotransformation of arsenate. The arsenic accumulation reached (819.66±11.25) μg·g-1 DW in Scenedesmus obliquus, which was higher than that in Microcystis aeruginosa of (355.95±8.31) μg·g-1 DW. Nano-TiO2 increased arsenic accumulation in these exposed algae species, and then reduced arsenic levels in the relative culture media. Furthermore, nano-TiO2 improved arsenic biotransformation in the exposed algae, and the organic arsenic was dimethylarsinous acid (DMA) and monomethylarsonous acid (MMA) in Microcystis aeruginosa and Scenedesmus obliquus, respectively. Additionally, the release of organic arsenic was lower from the exposed algae in nano-TiO2 treatments than in the control, indicating that nano-TiO2 couldn't stimulate the release of organic arsenic from algae under long-term exposure. These results could improve insights on the ecological risk of nano-TiO2 associated with arsenic in the environment.

Uptake and biotransformation of arsenate in the lichen Hypogymnia physodes (L.) Nyl.

The uptake and metabolism of arsenate, As(V), as a function of time and concentration were examined in the lichen Hypogymnia physodes (L.) Nyl. Lichen thalli were exposed to As(V) in the form of a solution. Exponential uptake of As(V) from 4 μg mL −1 As(V) solution was accompanied by constant arsenite, As(III), excretion back into the solution. Arsenate taken up into the lichens from 0, 0.1, 1, 10 μg mL −1 As(V) solutions was partially transformed into As(III), dimethylarsinic acid (DMA) and (mono)methylarsonic acid (MA). 48 h after exposure, the main arsenic compound in the lichens was DMA in 0.1, As(III) in 1 and As(V) in 10 μg mL −1 treatment. The proportion of methylated arsenic compounds decreased with increasing arsenate concentration in the exposure solution. These results suggest that at least two types of As(V) detoxification exist in lichens; arsenite excretion and methylation.

Biotransformation of Arsenate to Arsenosugars by Chlorella vulgaris.

Chlorella vulgaris was cultivated in a growth medium containing arsenate concentration of <0.01, 10, 100 and 1000 mg l−1. Illumination was carried out in 12 h cycles for 5 days. The health status of the culture was monitored by continuous pH and dissolved oxygen (DO) readings. Destructive sampling was used for the determination of biomass, chlorophyll, total arsenic and arsenic species. The chlorophyll a content, the DO and pH cycles were not significantly different for the different arsenate concentrations in the culture. In contrast, biomass production was significantly (p < 0.05) increased for the arsenic(V) treatment at 1000 mg l−1 compared with 100 mg l−1. The arsenic concentration in the algae increased with the arsenate concentration in the culture. However, the bioconcentration factor decreased a hundred-fold with increase of arsenate from the background level to 1000 mg l−1. The arsenic species were identified by using strong anion-exchange high-performance liquid chromatography–inductively coupled plasma mass spectrometry analysis after methanol/water (1 : 1) extraction. The majority (87–100%) of the extractable arsenic was still arsenate; arsenite was found to be between 1 and 6% of total extractable arsenic in the algae. In addition to dimethylarsinic acid, one unknown arsenical (almost co-eluting with methylarsonic acid) and three different arsenosugars have been identified for the first time in C. vulgaris growing in a culture containing a mixture of antibiotics and believed to be axenic. The transformation to arsenosugars in the algae is not dependent on the arsenate concentration in the culture and varies between 0.2 and 5% of total accumulated arsenic. Although no microbiological tests for bacterial contamination were made, this study supports the hypothesis that algae, and not associated bacteria, produce the arsenosugars. Copyright © 2003 John Wiley & Sons, Ltd.

Cellular uptake and biotransformation of arsenic V in transformed human cell lines HeLa S 3 and Hep G 2

The biotransformation of arsenate was studied in two human transformed cell lines (epithelial HeLa S 3 and hepatoma Hep G 2 cells) by the determination of several arsenic species both in the culture medium and in the cells. Arsenate reduction, which was observed in the two cell lines, was higher in Hep G 2 cells. Methylation appeared to be a minor pathway for HeLa cells, but was more important in the hepatoma cells.