The Role of Magnesium and Calcium Ions on Light Emission of Vibrio campbellii RMT1 and Glowing on Episcia lilacina
Leaves

The bioluminescent bacteria Vibrio campbellii RMT1 was isolated from the seawater of the Gulf of Thailand. It was investigated to study the possibility of glowing in the plant for alternative energy of light. In the experiment, magnesium sulfate (MgSO4) and calcium chloride (CaCl2) were added to the nutrient broth containing 1%NaCl and yeast extract to enhance the light emission of luminous bacteria. Results showed that MgSO4 and CaCl2 additions could enhance light intensity that were 1.27x108 Relative Light Unit (RLU) and 1.21x108 RLU, respectively, compared to NB + 1% NaCl + 0.15% yeast extract (1.12x108 RLU) and NB + 1% NaCl (5.40x107 RLU). It was possible that Mg and Ca ions can act as activators of luciferase to enhance light production in the lux operon. Interestingly, adding yeast extract and CaCl2 into the medium could extend the light emission time longer than adding MgSO4. Therefore, the application of CaCl2 to activate the light emission of luminous bacteria on Episcia lilacina leaves was observed. In the glowing plant, the leaves were covered with 0.5% agar medium including 1% NaCl + 0.3% CaCl2+ 0.15% yeast extract before applying luminous bacteria on the
leaves. Afterward, new nutrients were sprayed on the leaves every 6 h to extend the light emission time. The results showed the bioluminescent bacteria on the leaf could emit light for 24 h. Therefore, the addition of CaCl2 in nutrient solution could enhance and extend the light emission of Vibrio campbellii RMT1 on the leaf.