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Remediation of Selenium-Polluted Soils and Waters by Phytovolatilization
Published in Norman Terry, Gary Bañuelos, of Contaminated Soil and Water, 2020
Adel Zayed, Elizabeth Pilon-Smits, Mark deSouza, Zhi-Qing Lin, Norman Terry
For the genetic engineering of Indian mustard, we are using two different strategies. In one approach we try to speed up existing processes involved in Se metabolism by overexpressing possible rate-limiting enzymes. In the second approach we are attempting to introduce an additional metabolic pathway in Indian mustard, which now only exists in Se-hyperaccumulating plants, e.g., A. bisulcatus. For our first approach we have selected six target enzymes based on the Se volatilization pathway proposed earlier by Zayed and Terry (1992) (see Figure 4.1). Selenium and sulfur assimilation in plants is probably mediated by the same enzymes (Anderson, 1993; Läuchli, 1993), a hypothesis which is based on the chemical similarity of sulfur and selenium, as well as on biochemical and physiological competition studies with S and Se homologs. The six enzymes we have targeted for overexpression are as follows: (1) sulfate permease, the root membrane protein which takes up selenate; (2) ATP sulfurylase, which activates selenate in the reduction to selenite (Burnell, 1981); (3) glutathione reductase, an enzyme involved in the further reduction of selenite to selenide (Ng and Anderson, 1979); (4) cysteine synthase, which incorporates selenide into selenocysteine (Ng and Anderson, 1978); (5) cystathionine-13-lyase, which, along with cystathionine-y-synthase, mediates the conversion of selenocysteine to selenomethionine via the intermediate selenocystathionine (Burnell, 1981; Dawson and Anderson, 1988); and (6) SAM-synthetase, which generates the methyl donor, S-adenosylmethionine (SAM), for the methylation of selenomethionine (Lewis et al., 1974). Below, we summarize the results obtained thus far regarding each of the above specified enzymes.
Plant-Nanoparticles (Np) Interactions—a Review: Insights into Developmental, Physiological, and Molecular Aspects of Np Phytotoxicity
Published in Megh R Goyal, Sustainable Biological Systems for Agriculture, 2018
Although transcriptional analyses have been widely used to study the molecular basis of NP toxicity in a variety of organisms including microbes, humans, mammalian cell lines, and other model organisms,8 only limited investigations have been conducted to assess the molecular mechanism of the ENP-plant interactions and NP phytotoxicity. For example, gene expression analyses of the model plant A. thaliana by RT-PCR have provided new insights into the molecular mechanisms of plant response to Ag NPs. Dimkpa et al.29 investigated that exposure of commercial Ag NPs to wheat in a sand growth matrix induced plant defense response in Arabidopsis plants, as revealed by significant upregulation of pathogenesis-related (PR1, PR2, and PR5) genes involved in systemic acquired resistance (SAR).23 Similarly, the transcriptional response of A. thaliana exposed to Ag NPs were analyzed using whole genome cDNA expression microarrays, which resulted in upregulation of 286 genes and downregulation of 81 genes as compared to the control.62 Real-time PCR analysis showed significant transcriptional modulation of genes involved in sulfur assimilation and glutathione biosynthesis,i.e., adenosine triposphate sulfu- rylase (ATPS), 3’-phosphoadenosine 5’-phosphosulfate reductase (APR), sulfite reductase (SiR), cysteine synthase (CS), glutamate-cysteine ligase (GCL), glutathione synthetase (GS2) with upregulation of glutathione S-transferase (GSTU12), glutathione reductase (GR), and phytochelatin synthase (PCS1) genes.105 In another study by the same group, the expression of cell cycle genes proliferating cell nuclear antigen (PCNA) and DNA mismatch repair (MMR) were found to be modulated as the results of oxidative stress caused by Ag NPs exposure in A. thaliana.106 MicroRNAs (miRNAs) are a newly discovered post-transcriptional gene regulators, which belong to small endogenous class of noncoding RNAs (□ 20-22 nt). Interestingly, miRNAs have also been shown to play an important role in plant response to NPs by regulating gene expression. In a study by Frazier et al.,40 nano-TiO2 exposure to tobacco plants significantly affected the expression profiles of miRNAs, with miR395 and miR399 exhibiting the greatest fold changes of 285-fold and 143-fold, respectively.
Enhancement of Arthrospira sp. culturing for sulfate removal and mining wastewater bioremediation
Published in International Journal of Phytoremediation, 2023
M. Blanco-Vieites, D. Suárez-Montes, A. Hernández Battez, E. Rodríguez
Based on previous results, absorption mechanisms on external cellular walls did not decrease the sulfate concentration in wastewater, and neither did microbial activity due to the sterilization of wastewater and culture media. In an attempt to relate a decrease in sulfate with absorption mechanisms in A. maxima, cultures were harvested and freeze-dried by lyophilization. The yield of dried powder was 16% ± 2%, relative to the initial wet biomass. Total sulfur analysis showed that the experimental biomass contained a higher level of this element, up to 42% more than the control biomass (Figure 8). According to Mera et al. (2016), the sulfate content reduction in wastewater could be explained by sulfate ion uptake by living algae. Sulfur is required to synthetize a variety of organic molecules such as ferredoxins, vitamins (thiamine and biotin, among others) and amino acids, especially cysteine, which is considered the final metabolite of sulfur assimilation (Kumaresan et al. 2017; Leimkühler et al. 2017).
Sulfate and metals removal from acid mine drainage in a horizontal anaerobic immobilized biomass (HAIB) reactor
Published in Journal of Environmental Science and Health, Part A, 2020
Juliana Kawanishi Braga, Omar Mendes de Melo Júnior, Renata Piacentini Rodriguez, Giselle Patricia Sancinetti
By sequencing of 16S rRNA gene amplicons of the inoculum, a recent study observed 248 bacterial genera (predominance of Pseudomonas, Psychrobacter, Sporosarcina, Clostridium, Bacillus, Methanosaeta, Tannerella, Ornithobacterium, Candidatus Cloacomonas, Porphyromonas, Deinococcus, and Thermincola) with enzymatic machinery for all biogeochemical cycles.[72] The same study evaluated the functional diversity characterization of the inoculum by metagenomic sequencing and the authors detected the presence of sulfur metabolism. Sequences were assigned to sulfur oxidation, organic and inorganic sulfur assimilation, alkanesulfonate assimilation, and sulfate reduction-associated complexes.[72]