Biology subjects

Tolar, J. G.

Publications and source records attributed to Tolar, J. G..

2 recordsLinked to original sources

bioRxiv2023

Selective bioelectronic sensing of quinone pharmaceuticals using extracellular electron transfer in Lactiplantibacillus plantarum

Redox-active small molecules containing quinone functional groups play important roles as pharmaceuticals, but can be toxic if overdosed. Despite the need for a fast and quantitative method to detect quinone and its derivatives, current sensing strategies are often slow and struggle to differentiate between structural analogs. Leveraging the discovery that microorganisms use certain quinones to perform extracellular electron transfer (EET), we investigated the use of Lactiplantibacillus plantarum as a whole-cell bioelectronic sensor to selectively sense quinone analogs. By tailoring the native EET pathway in L. plantarum, we enabled quantitative quinone sensing of 1,4-dihydroxy-2-naphthoic acid (DHNA) - a gut bifidogenic growth stimulator. We found that L. plantarum could respond to environmental DHNA within seconds, producing electronic signals that cover a 106 concentration range. This sensing capacity was robust in different assay media and allowed for continuous monitoring of DHNA concentrations. In a simulated gut environment containing a mixed pool of quinone derivatives, this tailored EET pathway can selectively sense pharmacologically relevant quinone analogs, such as DHNA and menadione, amongst other structurally similar quinone derivatives. We also developed a multivariate model to describe the mechanism behind this selectivity and found a predictable correlation between quinone physiochemical properties and the corresponding electronic signals. Our work presents a new strategy to selectively sense redox-active molecules using whole-cell bioelectronic sensors and opens the possibility of using probiotic L. plantarum for bioelectronic applications in human health. Significant StatementQuinone-containing pharmaceuticals show toxicity at high concentrations, making it important to quickly and accurately measure their concentration while distinguishing between analogs. To address this problem, we leveraged recent discoveries in electroactive bacteria to develop a novel concept for whole-cell sensing. This concept combines selectivity and specificity, enabling differentiation between analogs based on the temporal dynamic of electron transfer in living cells. With this strategy, we achieved selective detection of pharmacologically relevant quinones with distinct electronic signals for each analog. These signals were deciphered by a multivariate model to provide insight into the specific physiochemical properties of each analog. We envision that this new concept can be applied to other analytes for faster and more efficient sensing using electroactive whole cells.

bioengineering↗

bioRxiv2022

The differing roles of flavins and quinones in extracellular electron transfer in Lactiplantibacillus plantarum

Lactiplantibacillus plantarum is a lactic acid bacteria that is commonly found in the human gut and fermented food products. Despite its overwhelmingly fermentative metabolism, this microbe can perform extracellular electron transfer (EET) when provided with an exogenous quinone, 1,4-dihydroxy-2-naphthoic acid (DHNA) and riboflavin. However, the separate roles of DHNA and riboflavin in EET in L. plantarum has remained unclear. Here we seek to understand the role of quinones and flavins for EET by monitoring iron and anode reduction in the presence and absence of these small molecules. We found that either addition of DHNA or riboflavin can support robust iron reduction, indicating electron transfer to extracellular iron occurs through both flavin-dependent and DHNA-dependent routes. Using genetic mutants of L. plantarum, we found that flavin-dependent iron reduction requires Ndh2 and EetA, while DHNA-dependent iron reduction largely relies on Ndh2 and PplA. In contrast to iron reduction, DHNA-containing media supported more robust anode reduction than riboflavin-containing media, suggesting electron transfer to an anode proceeds most efficiently through the DHNA-dependent pathway. Furthermore, we found that flavin-dependent anode reduction requires EetA, Ndh2, and PplA, while DHNA-dependent anode reduction requires Ndh2 and PplA. Taken together, we identify multiple EET routes utilized by L. plantarum and show that the EET route depends on access to environmental biomolecules and on the extracellular electron acceptor. This work expands our molecular-level understanding of EET in Gram-positive microbes and provides additional opportunities to manipulate EET for biotechnology. ImportanceLactic acid bacteria are named because of their nearly exclusive fermentative metabolism. Thus, the recent observation of EET activity - typically associated with anaerobic respiration - in this class of organisms has forced researchers to rethink the rules governing microbial metabolic strategies. Our identification of multiple routes for EET in L. plantarum that depend on two separate redox active small molecules expands our understanding of how microbes metabolically adapt to different environments to gain an energetic edge and how these processes can be manipulated for biotechnological uses. Understanding the role of EET in lactic acid bacteria is of great importance due to the significance of lactic acid bacteria in agriculture, bioremediation, food production, and gut health. Furthermore, the maintenance of multiple EET routes speak to the importance of this process to function in a variety of environmental conditions.

microbiology↗