Light spectrum and nitrogen availability are important regulators of cyanobacterial physiology, but their combined effect on photosynthetic control and stress adaptation is poorly understood. Leptolyngbya sp. MKU-05 was grown under five monochromatic lights (red, blue, green, yellow, and white) in nitrogen-sufficient (BG11) and nitrogen-depleted (BG11 0 ) medium to assess their impact on growth, pigment composition, oxidative stress response, and photosystem gene expression. In BG11 medium white light led to the maximum biomass accumulation (2.0 g L⁻ 1 ), whereas green light boosted growth (1.9 g L −1 and phycocyanin synthesis (122.58 mg g⁻ 1 DW) in BG11 0 medium. Nitrogen deprivation led to a significant increase in oxidative stress indicators, including 1.96 µmol mL −1 of hydrogen peroxide and 0.007 U mL −1 catalase activity under blue and red light, respectively. Photosystem-I gene expression reached its highest under yellow light (1.18-fold) in BG11; however, it transitioned to green light (0.73-fold) in BG11 0 . Photosystem-II was significantly activated to a 1.6-fold increase by blue light in BG11 and green light 1.2-fold in BG11 0 medium. Phycobilisomes expression remained consistently high under white light in both, highlighting its critical function in light harvesting regardless of nitrogen status. Collectively, these findings show the flexibility of Leptolyngbya sp. MKU-05 in reallocating resources under spectral and nutrient stress, providing insights into ecological resilience and further strategies for biotechnological applications.
Manoharan et al. (Thu,) studied this question.
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