Role of calcium acetate in promoting Vibrio campbellii bioluminescence and alleviating salinity stress in Episcia cupreata

Abstract

This study examines the role of calcium in regulating the bioluminescence of Vibrio campbellii PSU5986 and its potential to alleviate salt stress in plants, which has implications for developing light-emitting plants (LEPs). The effects of organic calcium acetate (C₄H₆CaO₄) were compared to inorganic calcium chloride (CaCl₂) and skim milk regarding their impact on bacterial bioluminescence and plant physiology. While skim milk induced the highest initial luminescence, both C₄H₆CaO₄ and CaCl₂ prolonged light emission for over 16 h. Notably, C₄H₆CaO₄ prevented leaf shrinkage, a condition observed with inorganic salts after 24 h. Periodic supplementation of C₄H₆CaO₄ (every 6 h) improved bacterial immobilization and colonization, extending luminescence over 4 cycles (24 h). Bacterial enumeration revealed colonization densities of approximately 6.82 × 10⁶ CFU cm⁻² within leaf tissues and 5.22 × 10¹¹ CFU cm⁻² on the leaf surface. Quantitative PCR analysis indicated that luxG exhibited significantly higher copy numbers than luxA and luxC, highlighting its critical role in bioluminescence through flavin reductase activity. Additionally, C₄H₆CaO₄ reduced salt-induced oxidative stress by increasing chlorophyll levels while decreasing carotenoid (40.00%), anthocyanin (36.94%), proline (14.13%), and malondialdehyde (21.84%) accumulation compared to NaCl-treated plants. These findings emphasize the potential of C₄H₆CaO₄ to sustain bacterial luminescence and enhance plant resilience, contributing to the advancement of LEP technology as a sustainable bioenergy alternative.