Journal
JOURNAL OF BIOTECHNOLOGY
Volume 325, Issue -, Pages 179-185Publisher
ELSEVIER
DOI: 10.1016/j.jbiotec.2020.10.029
Keywords
Azospirillum brasilense; Chlorella sorokiniana; reactive oxygen species; nitrogen limitation; copper stress
Categories
Funding
- USDA National Institute of Food and Agriculture
- Alabama Agricultural Experiment Station through Hatch Project [ALA0HIGGINS]
- Chinese Scholarship Council
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This study found that the plant growth promoting bacteria A. brasilense can reduce oxidative stress in green microalgae Chlorella sorokiniana during co-culture, resulting in increased chlorophyll content by secreting the auxin hormone. Additionally, A. brasilense can mitigate the effects of copper stress and nitrogen limitation on algae product accumulation.
In this study, we investigated oxidative stress in the green microalgae, Chlorella sorokiniana, in co-culture with the plant growth promoting bacteria (PGPB), Azospirillum brasilense. This relationship was studied in the absence of an exogenous stressor, under copper stress, and under nitrogen limitation stress. We confirmed that copper and nitrogen limitation induced algal oxidative stress and reductions in chlorophyll content. In all cases, the presence of A. brasilense lowered the accumulation of intracellular reactive oxygen species (ROS) while promoting chlorophyll content. This effect was driven, in part, by A. brasilense's secretion of the auxin hormone, indole-3-acetic acid, which is known to mitigate stress in higher plants. The findings of the present study show that stress mitigation by A. brasilense resulted in suppressed starch accumulation under nitrogen limitation stress and neutral lipid accumulation under copper stress. In fact, A. brasilense could almost completely mitigate oxidative stress in C. sorokiniana resulting from nitrogen limitation, with ROS accumulation rates comparable to the axenic control cultures. The biotechnological implication of these findings is that co-culture strategies with A. brasilense (and similar PGPB) are most effective for high growth applications. A second growth stage may be needed to induce accumulation of desired products.
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