Abstract:A 128-channel potentiostat for high-throughput microbial electrochemistry • Accompanying 128 gold electrode array (77 functional electrodes) • Anodic electroactive biofilms simultaneously grown at 11 electrode potentials (n = 7) • Midpoint potentials and charge transport parameters assessed by cyclic voltammetry • Most performant EABs grown just below anodic plateau (−0.3 V and −0.25 V vs. Ag/AgCl) A chip-based 128-channel potentiostat for high-throughput studies of bioelectrochemical systems: optimal electrod… Show more
“…Another example of well-plate array implementation was demonstrated by Yuan et al, ([25]), where extracellular electron transfer was coupled to the color change of the probe. Recently, Molderez et al [26] constructed a 128channel potentiostat connected to a printed circuit board (PCB) microarray. The entire microarray was immersed in an anolyte solution and supplied with a reference electrode to perform a high-throughput investigation pertaining to the effect of the anodic potential on electroactive biofilm growth.…”
The development of bioelectrochemical systems reinforces the necessity for the identification and engineering of electroactive bacteria with improved performance and novel biochemical properties. In this study, using a newly designed 96-well-plate array of microbial fuel cells (MFCs), we compared the electroactive capabilities of microbial communities derived from four mine drainages. The maximum power density of individual wells after two weeks of inoculation was 102 mW/m 3 , whereas the maximum current density was 1.6 A/m 3 . Transferring communities from individual wells into larger MFCs comprising low (20 mg/L) and high (200 mg/L) concentrations of Cu yielded maximum power densities of 445 and 58 mW/m 3 , respectively, with up to a 3.7 fold decrease in Cu 2+ ions within 24 h. Electrochemical data analysis revealed that microbial consortia can be distinguished based on their electrochemical profiles. Our results showed that a 96-well MFC array is a suitable platform for high-throughput screening, selection, and subsequent source of enriched electroactive consortia. The quantitative and comparative analysis followed by principal component analysis indicated that the initial environmental conditions, as well as physical and chemical parameters of the lakes were crucial to develop an efficient electroactive community. Further applications of the proposed platform include genetic engineering, phenotype screening, and mutagenesis studies of both microbial communities and single cultures. This is the first time that a high-throughput MFC platform is used to evaluate the performance of multiple electroactive consortia towards Cu removal.
“…Another example of well-plate array implementation was demonstrated by Yuan et al, ([25]), where extracellular electron transfer was coupled to the color change of the probe. Recently, Molderez et al [26] constructed a 128channel potentiostat connected to a printed circuit board (PCB) microarray. The entire microarray was immersed in an anolyte solution and supplied with a reference electrode to perform a high-throughput investigation pertaining to the effect of the anodic potential on electroactive biofilm growth.…”
The development of bioelectrochemical systems reinforces the necessity for the identification and engineering of electroactive bacteria with improved performance and novel biochemical properties. In this study, using a newly designed 96-well-plate array of microbial fuel cells (MFCs), we compared the electroactive capabilities of microbial communities derived from four mine drainages. The maximum power density of individual wells after two weeks of inoculation was 102 mW/m 3 , whereas the maximum current density was 1.6 A/m 3 . Transferring communities from individual wells into larger MFCs comprising low (20 mg/L) and high (200 mg/L) concentrations of Cu yielded maximum power densities of 445 and 58 mW/m 3 , respectively, with up to a 3.7 fold decrease in Cu 2+ ions within 24 h. Electrochemical data analysis revealed that microbial consortia can be distinguished based on their electrochemical profiles. Our results showed that a 96-well MFC array is a suitable platform for high-throughput screening, selection, and subsequent source of enriched electroactive consortia. The quantitative and comparative analysis followed by principal component analysis indicated that the initial environmental conditions, as well as physical and chemical parameters of the lakes were crucial to develop an efficient electroactive community. Further applications of the proposed platform include genetic engineering, phenotype screening, and mutagenesis studies of both microbial communities and single cultures. This is the first time that a high-throughput MFC platform is used to evaluate the performance of multiple electroactive consortia towards Cu removal.
“…The electrochemical reactor systems currently used for current production and drug testing involve relatively large volumes, making these systems infeasible for high-throughput screening of potential antimicrobials. Future studies should emphasize scaleddown systems, for example, using screen-printed electrodes or multi-well electrode systems (Molderez et al, 2020;Tahernia et al, 2020) that require minimum amounts of sample and antimicrobials. Such systems that exploit the electrogenic activity of pathogens could fast-track the discovery of antibiofilm drugs, as a large library of compounds could be rapidly screened.…”
Concerns regarding increased antibiotic resistance arising from the emergent properties of biofilms have spurred interest in the discovery of novel antibiotic agents and techniques to directly estimate metabolic activity in biofilms. Although a number of methods have been developed to quantify biofilm formation, real-time quantitative assessment of metabolic activity in label-free biofilms remains a challenge. Production of electrical current via extracellular electron transport (EET) has recently been found in pathogens and appears to correlate with their metabolic activity. Accordingly, monitoring the production of electrical currents as an indicator of cellular metabolic activity in biofilms represents a new direction for research aiming to assess and screen the effects of antimicrobials on biofilm activity. In this article, we reviewed EET-capable pathogens and the methods to monitor biofilm activity to discuss advantages of using the capability of pathogens to produce electrical currents and effective combination of these methods. Moreover, we discussed EET mechanisms by pathogenic and environmental bacteria and open questions for the physiological roles of EET in pathogen's biofilm. The present limitations and possible future directions of in situ biofilm metabolic activity assessment for large-scale screening of antimicrobials are also discussed.
“…Finding this machinery has been hindered by the lack of high-throughput assays for electron uptake and the challenge of developing screens for non-growth-related phenotypes. Even with recent advances in high-throughput electrode arrays 19 , searching through the thousands of genes in even a single microbial genome by direct electrochemical measurements remains impractical. Fig.…”
Extracellular electron transfer (EET) could enable electron uptake into microbial metabolism for the synthesis of complex, energy dense organic molecules from CO2 and renewable electricity1–6. Theoretically EET could do this with an efficiency comparable to H2-oxidation7,8 but without the need for a volatile intermediate and the problems it causes for scale up9. However, significant gaps remain in understanding the mechanism and genetics of electron uptake. For example, studies of electron uptake in electroactive microbes have shown a role for the Mtr EET complex in the electroactive microbe Shewanella oneidensis MR-110–14, though there is substantial variation in the magnitude of effect deletion of these genes has depending on the terminal electron acceptor used. This speaks to the potential for previously uncharacterized and/or differentially utilized genes involved in electron uptake. To address this, we screened gene disruption mutants for 3667 genes, representing ≈99% of all nonessential genes, from the S. oneidensis whole genome knockout collection using a redox dye oxidation assay. Confirmation of electron uptake using electrochemical testing allowed us to identify five genes from S. oneidensis that are indispensable for electron uptake from a cathode. Knockout of each gene eliminates extracellular electron uptake, yet in four of the five cases produces no significant defect in electron donation to an anode. This result highlights both distinct electron uptake components and an electronic connection between aerobic and anaerobic electron transport chains that allow electrons from the reversible EET machinery to be coupled to different respiratory processes in S. oneidensis. Homologs to these genes across many different genera suggesting that electron uptake by EET coupled to respiration could be widespread. These gene discoveries provide a foundation for: studying this phenotype in exotic metal-oxidizing microbes, genetic optimization of electron uptake in S. oneidensis; and genetically engineering electron uptake into a highly tractable host like E. coli to complement recent advances in synthetic CO2 fixation15.
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