Date of Award
Campus Access Dissertation
Doctor of Philosophy in Biological Sciences (PhD)
Administrative Home Department
Department of Biological Sciences
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Arsenic is one of the most toxic environmental pollutants, classified as a Class I carcinogen. Anthropogenic activities such as industrial and agricultural applications have led to an increase in arsenic contamination of soils. The work presented here is a systematic approach to evaluating and mitigating the health impacts of arsenic and exploring the role of the root microbiome of the arsenic hyperaccumulating plant, the Chinese Brake fern (Pteris vittata L.), in enhanced arsenic uptake and tolerance. This research deals with three aspects of soil arsenic pollution, 1. Determine the human health impact of arsenic due to contact exposure using a human skin cell culture model, 2. Develop a novel phytoremediation technique to mitigate arsenic exposure through rice consumption, and 3. Exploring the plant-microbe interactions in enhancing arsenic tolerance and uptake by the hyperaccumulator, P. vittata.
We used human skin cell culture and soil geochemical techniques to determine the effect of soil arsenic exposure through dermal contact. Immokalee soil from Florida was spiked with four concentrations of arsenic based on ten-year use of arsenical pesticides. Our data indicated that keratinocyte cells were more susceptible to arsenic-induced cellular transformation than fibroblasts. In addition, higher concentrations of soil arsenic impacted specific cellular responses such as cell viability, cell migration, and epithelial-to-mesenchymal transition, and induced changes in the expression of proteins related to these functions. The in-vitro model developed in this study can be used as a quick, inexpensive, and reliable approach to determine the toxicity of soil contaminants.
Exposure to arsenic from a diet of contaminated rice is a widespread problem and a serious concern in several parts of the world. We developed a crop rotation method of alternating rice with the arsenic hyperaccumulator, P. vittata, to reduce arsenic concentrations in rice grains. Our results show that at the end of two crop rotation cycles, there was a 67% and 35% decrease in arsenic in rice grains and soil, respectively.
Interactions between hyperaccumulators and metal(oid)-resistant microbes in the rhizosphere have generated much research interest due to their application potential in plant-based environmental remediation techniques. We compared root endophytic, rhizospheric and bulk soil microbial communities between P. vittata and non-accumulator Pteris ensiformis Burm. Arsenic-tolerant bacteria like Steroidobacter, Cohnella, and Streptomyces were present in the root endophytes of P. vittata but absent in P. ensiformis. These findings suggest that the arsenic hyperaccumulator specifically recruits a microbial community that enhances its tolerance and uptake of arsenic. The root microbiome of hyperaccumulators could provide valuable insight into improving the efficiency of metal uptake in plants growing in polluted soil.
Warke, Manas, "Evaluating soil Arsenic toxicity using an in vitro cell culture model and exploring the Pteris vittata microbiome in Arsenic mitigation using phytotechnology", Campus Access Dissertation, Michigan Technological University, 2022.
Available for download on Friday, October 20, 2023