Abstract:

Microbial fuel cells (MFCs) represent a promising avenue for sustainable energy production by harnessing the metabolic activity of microorganisms. In this study, a novel design of MFC—a Microfluidic Benthic Micro- bial Fuel Cell (MBMFC)—was developed, fabricated, and tested to evaluate its electrical energy generation. The design focused on balancing microfluidic architecture and wiring procedures with microbial community dynamics to maximize power output and allow for upscaling and thus practical implementation. The testing phase involved experimentation to evaluate the performance of the MBMFC. Microbial feedstock was varied to assess its impact on power generation. The designed MBMFC represents a promising advancement in the field of bioenergy generation. By integrating innovative design principles with advanced fabrication techniques, this study demonstrates a systematic approach to optimizing MFC performance for sustainable and clean energy production.

Abstract:

Ιn all living organisms, antioxidant defenses are largely orchestrated by the thioredoxin (Trx) and glutaredoxin (Grx) systems. The Trx system of Escherichia coli (E. coli) is comprised of Trx1 and Trx2, both reduced by thioredoxin reductase (TrxR). The Grx system consists of four Grxs (Grx1, Grx2, Grx3, and Grx4) all reduced by glutathione (GSH) except for Grx4, which is reduced by TrxR. Under normal conditions, the GSH reductase of the Grx system keeps GSH at its reduced state, while NADPH⁺ provides the electrons for all reductions in both the Trx and Grx systems. The role of the E. coli Trx system is widely known, while the established functions of the Grx system are mainly reflected in the ability of Grx1 to reduce ribonucleotide reductase Ia (RRIa). E. coli Grx3, (encoded by grxC) may also reduce RRIa in vitro but with slow kinetics. The molecule may account up to 0.4 % of total soluble protein and has been the subject of extensive structural studies. Its biological function however remains unknown. Herein, affinity chromatography with monothiol Grx3 was used to detect the interactions of Grx3 with other proteins. Different types of interactions were identified (covalent, weak and strong non-covalent) that suggested novel functions for Grx3. In silico approaches were employed and gave a score 45 % for the selected interactions examined. Total protein extracts from the null mutant for grxC and the wild-type strain were also compared. The overall findings suggest that Grx3 is involved in various metabolic processes, protein synthesis, and stress responses expanding the recognized functions of Grx3 beyond the reduction of RRIa.

Biography:

Charalampos Bompas is a biochemist-biotechnologist, that has completed his MSc in Applications of Molecular Biology-Genetics-Diagnostic Markers at the Department of Biochemistry and Biotechnology, University of Thessaly. He has published one scientific paper and is currently enrolled in a PhD program in the Division of of Organic Chemistry, Biochemistry and Natural Products, Depatment of Chemistry, Univesrity of Patras.

Abstract:

The glutaredoxin (Grx) and thioredoxin (Trx) systems keep intracellular environments at a reduced state in almost all organisms, including viruses. In Escherichia coli (E. coli), the Grx system relies on NADPH⁺ to reduce GSH reductase (GR), the latter reducing oxidized diglutathione to glutathione (GSH) which in turn reduces cytosolic Grxs, the electron donors for different intracellular substrates. In the Trx system, GR and GSH are replaced by Trx reductase (TrxR). Three of the Grxs of E. coli (Grx1, 2, 3) are reduced by GSH, while Grx4 is likely reduced by TrxR. Trx1 and Grx1 from E. coli may reduce ribonucleotide reductase Ia to ensure a constant supply of deoxyribonucleotides for the synthesis of DNA. The role of the other three Grxs is relatively unknown especially for Grx2 that may amount up to 1 % of total cellular protein in the stationary phase of growth. The protein is a potent general antioxidant, but no specific functions have been attributed to it. Herein, affinity chromatography of cellular extracts on immobilized monothiol Grx2, followed by LC-MS/MS analysis of the resulting eluates was employed to identify protein ligands that could provide insights in the biological role of Grx2. Ionic, strong non-covalent and covalent (disulfide) interactions with relevant proteins were detected. Selected identified ligands were subjected to in silico docking with monothiol Grx2 resulting in a success rate of 63 %. In other experiments, total proteomes from E. coli cells lacking the gene for Grx2 (grxB^– strains) were compared to those of wild type. The affinity derived ligands and the comparison of the two proteomes suggest that Grx2 is involved in protein synthesis, nucleotide metabolism, DNA damage repair, stress responses, and various metabolic processes. Grx2 appears thus as a multipartner protein that may participate in a wide range of biological pathways, beyond its known general antioxidant function

Biography:

Eleni Poulou-Sidiropoulou is a biologist, that has completed her MSc in Biomedical Sciences at the Department of Medicine, University of Patras. She has worked as an intern at the Department of Oncology-Pathology, Karolinska Istitutet and as a research assistant at the National Hellenic Researsch Foundation and she has published three scientific papers and is currently enrolled in a PhD program in the Division of of Organic Chemistry, Biochemistry and Natural Products, Depatment of Chemistry, Univesrity of Patras.

Abstract:

The euhalophyte plant Suaeda altissima is unique in the way of its salinity tolerance: the plant is able to grow and proliferate at soil salinities of up to 1 M NaCl. The aspects of its nitrogen nutrition are important from the practical point for transfer to agriculturally valuable crops and the point of general biology. Earlier we reported the cloning of SaNPF6.3 gene, a putative ortholog of the dual-affinity nitrate (NO₃⁻) transporter gene AtNPF6.3/AtNRT1.1 from Arabidopsis thaliana, from the euhalophyte Suaeda altissima. The nitrate transporting activity of SaNPF6.3 was studied by heterologous expression of the gene in the yeast Hansenula (Ogataea) polymorpha mutant strain Δynt1 lacking the original nitrate transporter. Expression of SaNPF6.3 in Δynt1 cells rescued their ability to grow on the selective medium in the presence of nitrate and absorb nitrate from this medium. Confocal microscopy of the yeast cells expressing the fused protein GFP-SaNPF6.3 revealed GFP (green fluorescent protein) fluorescence localized predominantly in the cytoplasm and/or vacuoles (Nedelyaeva et al., 2023 doi: 10.3390/membranes13100845). Here we report the cloning of two genes of nitrate transporters SaNRT2.1 and SaNRT2.5, putative orthologs of high-affinity nitrate transporter genes AtNRT2.1 and AtNRT2.5 from Arabidopsis thaliana, from the euhalophyte Suaeda altissima. An attempt to demonstrate nitrate transporting activity of SaNRT2.1 or SaNRT2.5 by heterologous expression of the genes in the yeast Hansenula polymorpha mutant strain Δynt1 was not successful but the experiments are under way to show that SaNRT2.1 and SaNRT2.5 require interactions with SaNRT3 for their activity. The expression patterns of SaNRT2.1 and SaNRT2.5 were studied in S. altissima plants that were grown in hydroponics under either low (0.5 mM) or high (15 mM) nitrate and salinity from 0 to 750 mM NaCl. The growth of the plants was strongly inhibited by low nitrogen supply while stimulated by NaCl; it peaked at 250 mM NaCl for high nitrate and at 500 mM NaCl for low nitrate. Salinity increased expression of both SaNRT2.1 and SaNRT2.5 under low nitrate. SaNRT2.1 peaked in roots at 500 mM NaCl with 15-fold increase; SaNRT2.5 peaked in roots at 500 mM NaCl with 150-fold increase. It is suggested that SaNRT2.5 ensures effective nitrate uptake by roots and functions as an essential high-affinity nitrate transporter to support growth of adult S. altissima plants under nitrogen deficiency.