An Innovative Approach to the Planet’s Degrading Environments: Engineering a Novel Strain of Rhizobacteria to Ensure Plant Productivity under Worsening Abiotic Stress Conditions

    Author Name(s)

    Selin Kocalar
    Aylin Salahifar

    Faculty Advisor(s)

    Edward Njoo

    Abstract

    To address environmental stressors such as heavy metal contamination, soil salinity, and rising temperatures, the relationship between rhizobacterial strain Bacillus cereus and survival of Arabidopsis thaliana under abiotic stress was probed and optimized through genetic engineering. Plant growth measurements, chlorophyll content studies by UV-visible spectrophotometry, profiles of 15 key metabolites using gas chromatography-mass spectroscopy, quantitative gene expression screens, and 1-aminocyclopropane-1-carboxylate (ACC) deaminase-activity assays were performed in triplicate prior to abiotic stress, post-abiotic stress, and post-abiotic stress during rhizobacterial treatment. It was hypothesized that abiotic stress would alter measurements of A. thaliana productivity, however, the introduction of the bacterium would allow these plant measurements to begin to return to pre-stress levels, which results partially supported. Based on metabolite level trends observed in preliminary studies, which suggested a potential link to rhizobacterial ACC deaminase activity, a strain of B. cereus was engineered using Gibson cloning to overexpress the acdS gene encoding for ACC deaminase. Treatment of A. thaliana with the edited strain resulted in an average 10% more growth, 25% greater chlorophyll production, and 13% greater soil ACC-deaminase activity, while the genes associated with heavy metal, heat, and salinity stress response were promoted by 56%, 24%, and 35%, respectively, compared to wild-type treatment. The study was concluded with a HTML/JavaScript analysis of publicly-available datasets, revealing that ~40% of countries are at high risk of crop loss associated with the studied factors, thus demonstrating the significant global need for the implementation of solutions such as the acdS-edited B. cereus strain to mitigate current and future environmental crises.

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