Two plant-hosted whole-cell bacterial biosensors for detection of bioavailable Cr(VI)

  • Romeu FranciscoEmail author
  • Rita Branco
  • Stefan Schwab
  • Ivo Baldani
  • Paula V. Morais
Original Paper


Metal whole-cell biosensors (WCBs) have been reported as very useful tools to detect and quantify the presence of bioavailable fractions of certain metals in water and soil samples. In the current work, two bacterial WCBs able to report Cr(VI) presence and plants growing on Cr(VI)-enriched soil/medium were used to assess the potential transfer of this metal to organisms of higher trophic levels, and the risk of transfer to the food chain. To do it, the functionality of the WCBs within tissues of inoculated plants in contact with Cr(VI)-contaminated soil and water was studied in vitro and in a controlled greenhouse environment. One WCB was the previously described Ochrobactrum tritici pCHRGFP2 and the second, Nitrospirillum amazonense pCHRGFP2, is a newly engineered naturally-occurring endophytic microorganism. Three rice varieties (IAC 4440, BRS 6 CHUÍ, IRGA 425) and one maize variety (1060) were tested as hosts and subjected to Cr(VI) treatments (25 μM), with different results obtained. Inoculation of each WCB into plants exposed to Cr(VI) showed GFP expression within plant tissues. WCBs penetrated the root tissues and later colonized the shoots and leaves. In general, a higher fluorescence signal was detected in roots, together with a higher Cr content and denser WCB colonization. Best fluorescence intensities per plant biomass of shoots were obtained for plant host IRGA 425. Therefore, by analyzing colonized tissues, both WCBs allowed the detection of Cr(VI) contamination in soils and its transfer to plants commonly used in crops for human diet.

Graphic abstract


Whole-cell biosensors Ochrobactrum tritici Nitrospirillum amazonense Maize Rice Chromium 



This work was financed by the “Science without Borders” program of Brazilian government through Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), process #400756/2012–9, and also R.F. “pós-doutorado júnior (PDJ)” fellowship #160619/2012–2, and R.B. “pesquisador visitante especial (PVE)” fellowship #304009/2012–1 and project ERA-MIN 02 2015 BioCriticalMetals. We thank Juliana Meneses, Isabel Alves, and Ednelson Gomes (Embrapa Agrobiologia) for help on sample digestion, and Nelson Moura Brasil and Jair Guedes (Universidade Federal Rural do Rio de Janeiro) for helping on atomic absorption spectrometry analyses.

Supplementary material

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Supplementary file4—Figure S3 (TIFF 1352 kb)
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Supplementary file5—Supplementary Figure Captions and Table S1 (DOCX 37 kb)


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Copyright information

© Springer Nature B.V. 2019

Authors and Affiliations

  1. 1.CEMMPRE – Centre for Mechanical Engineering, Materials and ProcessesUniversity of CoimbraCoimbraPortugal
  2. 2.Department of Life Sciences, FCTUCUniversity of CoimbraCoimbraPortugal
  3. 3.Embrapa AgrobiologiaSeropédicaBrazil

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