Effect of Priestia endophytica on the metabolites accumulation in chicory and lettuce plants cultivated in vitro

The influence of the culture medium without bacterial cells, obtained after the cultivation of endophytic bacteria Priestia endophytica UCM B-5715, on the growth and synthesis of some metabolites in lettuce and chicory seedlings under in vitro conditions was studied. Bacteria were cultivated in liquid LB medium at 37 oC for 24 h with periodic stirring. The culture fluid was separated from the cell biomass. For preparing the test solution, the supernatant was sterilized by filtration through a filter with a pore diameter of 0.2 mu m (Sartorius, Minisart) and diluted with sterile distilled water. The 20% culture fluid (30 mu l/plant) was applied to 3-day-old seedlings. In 28 days root and shoot weights of treated chicory plants were 54.3 +/- 6.9 and 260.0 +/- 20.2 mg, respectively (8.0 +/- 0.7 and 91.4 +/- 7.0 mg for the control plants). Total flavonoid content and antioxidant activity increased only in chicory plants after the addition of the test solution. Significant changes in the metabolism of treated plants were detected. In the treated lettuce plants asparagine content increased compared to the control (90 vs 22 mu g/g, p < 0.1). The median content of fructose was also higher in treated lettuce and chicory plants (1469 vs 73 mu g/g and 2278 vs 1051 mu g/g). Therefore, the use of culture fluid obtained after the cultivation of P. endophytica UCM B-5715 stimulated the growth of lettuce and chicory plants, affecting the synthesis of some compounds in single-treated plants. These results indicate the potential of compounds excreted during bacterial growth to create natural growth stimulators.