{"paper_id":"0251db3e-4099-4acd-9ba2-7b7b2c0ba9b2","body_text":"N-ethylmaleimide (NemA) reductase mediated hexavalent chromium transformation by Plant growth promoting Bacillus tropicus V1 facilitates post stimulatory response in tomato (Solanum lycopersicum) cultivated in chromium contaminated soil | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article N-ethylmaleimide (NemA) reductase mediated hexavalent chromium transformation by Plant growth promoting Bacillus tropicus V1 facilitates post stimulatory response in tomato (Solanum lycopersicum) cultivated in chromium contaminated soil Vivek Patel, Mohini Pimpalse, Naga Rathna Supriya Guthikonda This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7055822/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract In this study, a Cr VI -tolerant Bacillus tropicus V1, was isolated from soil and evaluated for its plant growth promoting and bioremediation potential. The strain produced IAA (46.91 ± 5.69 µg/ml), gibberellic acid (32.50 ± 5.72 µg/ml), ammonia (2.29 ± 0.46 µg/ml) and solubilized phosphate (42.74 ± 5.23 µg/ml), along with ACC deaminase activity (0.693 ± 0.06 µmol/min/mg protein). B. tropicus V1 exhibited a Cr VI reduction efficiency of 63.81 ± 0.75%. The NemA gene showed 1.8-fold upregulation under Cr VI stress, indicating an inducible detoxification response. Molecular docking revealed strong binding affinity of the NemA:FMN complex (-6.1 kcal/mol), stabilized by FMNH 2 , Cr VI , and key active site residues. This study highlights a flavin-dependent redox mechanism where NemA catalyses the enzymatic reduction of Cr VI to the less toxic Cr III via electron transfer. Field trials on Solanum lycopersicum under Cr VI stress revealed significant growth enhancement in B. tropicus -induced plants: suggesting shoot width increased by 31%, shoot length by 22% and root length by 33% relative to uninoculated controls. Cr VI reduced chlorophyll content by 15% whereas B. tropicus treatment elevated it by 47% over control and 23% under stress. Carotenoids declined 1.51-fold with co-treatment. Antioxidant enzymes (APX, POD, and SOD) were upregulated in treated plants. Total Cr accumulation in controls followed an apoplastic barrier pattern, with highest accumulation in roots (12.79 ppm), followed by shoots (4.33 ppm) and leaves (1.30 ppm). In contrast, B. tropicus treatment significantly reduced Cr levels: roots (9.76 ppm), shoots (2.74 ppm) and leaves (0.841 ppm), established its potential for Cr VI bioremediation and phyto-protection. Cr accumulation CrVI biotransformation N-ethylmaleimide (NemA) reductase PGP traits Full Text Supplementary Files Supplementarymaterial.docx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {\"props\":{\"pageProps\":{\"initialData\":{\"identity\":\"rs-7055822\",\"acceptedTermsAndConditions\":true,\"allowDirectSubmit\":true,\"archivedVersions\":[],\"articleType\":\"Research Article\",\"associatedPublications\":[],\"authors\":[{\"id\":492884496,\"identity\":\"abdd959e-ba37-40e7-8f29-8f5b7b833059\",\"order_by\":0,\"name\":\"Vivek 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The strain produced IAA (46.91\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;5.69 \\u0026micro;g/ml), gibberellic acid (32.50\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;5.72 \\u0026micro;g/ml), ammonia (2.29\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;0.46 \\u0026micro;g/ml) and solubilized phosphate (42.74\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;5.23 \\u0026micro;g/ml), along with ACC deaminase activity (0.693\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;0.06 \\u0026micro;mol/min/mg protein). \\u003cem\\u003eB. tropicus\\u003c/em\\u003e V1 exhibited a Cr\\u003csup\\u003eVI\\u003c/sup\\u003e reduction efficiency of 63.81\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;0.75%. The NemA gene showed 1.8-fold upregulation under Cr\\u003csup\\u003eVI\\u003c/sup\\u003e stress, indicating an inducible detoxification response. Molecular docking revealed strong binding affinity of the NemA:FMN complex (-6.1 kcal/mol), stabilized by FMNH\\u003csub\\u003e2\\u003c/sub\\u003e, Cr\\u003csup\\u003eVI\\u003c/sup\\u003e, and key active site residues. This study highlights a flavin-dependent redox mechanism where NemA catalyses the enzymatic reduction of Cr\\u003csup\\u003eVI\\u003c/sup\\u003e to the less toxic Cr\\u003csup\\u003eIII\\u003c/sup\\u003e via electron transfer. Field trials on \\u003cem\\u003eSolanum lycopersicum\\u003c/em\\u003e under Cr\\u003csup\\u003eVI\\u003c/sup\\u003e stress revealed significant growth enhancement in \\u003cem\\u003eB. tropicus\\u003c/em\\u003e-induced plants: suggesting shoot width increased by 31%, shoot length by 22% and root length by 33% relative to uninoculated controls. Cr\\u003csup\\u003eVI\\u003c/sup\\u003e reduced chlorophyll content by 15% whereas \\u003cem\\u003eB. tropicus\\u003c/em\\u003e treatment elevated it by 47% over control and 23% under stress. Carotenoids declined 1.51-fold with co-treatment. Antioxidant enzymes (APX, POD, and SOD) were upregulated in treated plants. Total Cr accumulation in controls followed an apoplastic barrier pattern, with highest accumulation in roots (12.79 ppm), followed by shoots (4.33 ppm) and leaves (1.30 ppm). 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