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<p>Titanium dioxide nanoparticles (n-TiO₂) have emerged as potent modulators of photosynthetic activity in cyanobacteria; however, their strain-specific physiological effects in <i>Fremyella diplosiphon</i>, a model cyanobacterium, remain unexplored. In this study, we investigated the impact of n-TiO<sub>2</sub> on growth, pigment autofluorescence, photosynthetic capacity, reactive oxygen species (ROS) generation and ATP synthase activity in <i>F. diplosiphon</i> strains B481-SD (overexpressed with the sterol desaturase gene) and B481-WT (wild type). Growth as a measure of optical density was maximal in B481-SD at 2.0&#xa0;mg/L (0.67 ± 0.01) and in B481-WT at both 2.0 (0.55 ± 0.01) and 16&#xa0;mg/L (0.52 ± 0.01) n-TiO<sub>2</sub> on day 12. Pigment accumulation over 15 days revealed enhanced phycocyanin (1300 ± 2) and chlorophyll <i>a</i> (890 ± 5) levels in 2.0&#xa0;mg/L n-TiO₂-treated B481-SD while no significant changes were observed in B481-WT. Photosynthetic efficiency (<i>Fv/Fm</i>) of B481-SD treated with 2.0&#xa0;mg/L n-TiO₂ was significantly higher on days 6, 9, and 12. ROS quantification using the 2′,7′dichlorodihydrofluorescein diacetate assay revealed significantly higher levels in B481-WT at 2.0&#xa0;mg/L (260 ± 5), whereas B481-SD exhibited lower ROS levels at 2.0 (210 ± 2) and 16&#xa0;mg/L (220 ± 4) n-TiO<sub>2</sub> on day 15. Additionally, immunodetection analysis of ATP synthase revealed significantly enhanced expression in <i>F. diplosiphon</i> B481-SD treated with 0.5, 2.0, and 128&#xa0;mg/L n-TiO₂ compared to the untreated control. Visualization of cell-n-TiO₂ interactions using field emission scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy revealed a strong absorption for titanium, with an atomic percentage of 0.32%. These findings demonstrate strain-specific responses of <i>F. diplosiphon</i> to n-TiO₂, paving the way for scale-up cultivation to enhance cyanobacteria-derived bioproducts.</p>

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Strain-Specific Impact of Titanium Dioxide Nanoparticles on Fremyella Diplosiphon Physiological and Metabolic Responses

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年12月1日

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  • Mst Sayadujjhara,
  • Yavuz S. Yalcin,
  • William Ghann,
  • Jamal Uddin,
  • Viji Sitther

摘要

Titanium dioxide nanoparticles (n-TiO₂) have emerged as potent modulators of photosynthetic activity in cyanobacteria; however, their strain-specific physiological effects in Fremyella diplosiphon, a model cyanobacterium, remain unexplored. In this study, we investigated the impact of n-TiO2 on growth, pigment autofluorescence, photosynthetic capacity, reactive oxygen species (ROS) generation and ATP synthase activity in F. diplosiphon strains B481-SD (overexpressed with the sterol desaturase gene) and B481-WT (wild type). Growth as a measure of optical density was maximal in B481-SD at 2.0 mg/L (0.67 ± 0.01) and in B481-WT at both 2.0 (0.55 ± 0.01) and 16 mg/L (0.52 ± 0.01) n-TiO2 on day 12. Pigment accumulation over 15 days revealed enhanced phycocyanin (1300 ± 2) and chlorophyll a (890 ± 5) levels in 2.0 mg/L n-TiO₂-treated B481-SD while no significant changes were observed in B481-WT. Photosynthetic efficiency (Fv/Fm) of B481-SD treated with 2.0 mg/L n-TiO₂ was significantly higher on days 6, 9, and 12. ROS quantification using the 2′,7′dichlorodihydrofluorescein diacetate assay revealed significantly higher levels in B481-WT at 2.0 mg/L (260 ± 5), whereas B481-SD exhibited lower ROS levels at 2.0 (210 ± 2) and 16 mg/L (220 ± 4) n-TiO2 on day 15. Additionally, immunodetection analysis of ATP synthase revealed significantly enhanced expression in F. diplosiphon B481-SD treated with 0.5, 2.0, and 128 mg/L n-TiO₂ compared to the untreated control. Visualization of cell-n-TiO₂ interactions using field emission scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy revealed a strong absorption for titanium, with an atomic percentage of 0.32%. These findings demonstrate strain-specific responses of F. diplosiphon to n-TiO₂, paving the way for scale-up cultivation to enhance cyanobacteria-derived bioproducts.