Development of light-emitting Episcia lilacina leaf by applying Vibrio campbellii RMT1 and extending the glowing by CaCl2 and yeast extract.

ABSTRACT

Glowing Episcia lilacina was generated through foliar application of the bioluminescent bacterium Vibrio campbellii RMT1. Firstly, different nutrient formulas were tested, incorporating yeast extract and various inorganic salts, such as CaCl2, MgCl2, MgSO4, KH2PO4, K2HPO4, and NaCl, in order to enhance bacterial growth and light emission. The combination of 0.15% of yeast extract and 0.3% of CaCl2 in a nutrient broth (NB) + 1% NaCl medium extended light emission to 24 h and resulted in higher light intensity compared to other combinations of yeast extract and inorganic salts. The peak intensity reached approximately 1.26 × 108 relative light units (RLU) at 7 h. The optimal presence of inorganic salt ions likely contributed to enhanced light emission, while the yeast extract acted as a nutrient source. Secondly, the effect of proline on salt-induced stress symptoms was investigated by applying 20 mM proline to the glowing plant. Additionally, a 0.5% agar nutrient was spread on the leaves prior to bacteria application to support bacterial growth and penetration. Exogenous proline application led to a significant accumulation of proline in plant cells, resulting in decreased malondialdehyde (MDA) levels. However, the proline accumulation also reduced the light intensity of the bioluminescent bacteria. This study demonstrates the potential for generating light on a living plant using bioluminescent bacteria. Further understanding of the interaction between plants and light-emitting bacteria could contribute to the development of sustainably light-emitting plants.