The cadCA and cadB/DX operons are possibly induced in cadmium resistance mechanism by Frankia alni ACN14a

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Rehan, Medhat | Alhusays, Ahmed | Serag, Ahmed | Boubakri, Hasna | Pujic, Petar | Normand, Philippe

Edité par CCSD ; Pontificia Universidad Católica de Valparaíso -

International audience. Background: Cadmium (Cd2+) is one of the highly toxic heavy metals and is considered as a carcinogenic agent. Our aim was to confirm the ability of Frankia alni ACN14a to resist Cd2+ and to determine the genes involved in the resistance mechanism.Results: F. alni ACN14a and Frankia casuarinae CcI3 hyphae showed up to 10 and 22 times Cd2+ accumu-lation when exposed to 1 mM Cd2+, respectively. Scanning electron microscopy (SEM) exhibited a stable Cd2+ precipitate on the cell surface, and the increase in Cd2+ weight level reached 16.45% when evaluated with SEM-EDAX analysis. The following two potential Cd2+ operons were identified: 1. cadCA operon, which encodes a copper-transporting P-type ATPase A (cadA, FRAAL0989) and an ArsR family regulator (cadC, FRAAL0988), with 37-and 70-fold increase in their expression by qRT-PCR, respectively and 2. cadB/DX, which encodes a putative cobalt-zinc-cadmium resistance protein (cadD, FRAAL3628) and heavy metal-associated domain protein (cadX, FRAAL3626), with 22-and 16-fold upregulation when exposed to Cd2+ stress. Conclusions: Cd2+ tolerance by F. alni ACN14a involved efflux of Cd2+ outside the cells and binding it to the membrane surface. Our results indicate the existence of two cadmium-resistance mechanisms in Frankia strains, which support the idea of using them as a bioremediation agent. How to cite: Rehan M, Alhusays A, Serag AM, et al. The cadCA and cadB/DX operons are possibly induced in cadmium resistance mechanism by Frankia alni ACN14a. Electron J Biotechnol 2022;60. https://doi.org/ 10.1016/j.ejbt.2022.09.006.

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