Synthesis of indole 3 acetic acid during co-cultivation of yeast and bacteria

The work is dedicated to the study of yeast and bacterial strains that are potential components for developing bio-preparations for plants. Experiments involving the co-cultivation of bacteria and yeast capable of stimulating plant growth provide a basis for the development of complex bio-preparations that can impact agricultural crops and be evaluated based on their phytohormonal activity. The study evaluates the possibility of synthesizing indole-3-acetic acid during the co-cultivation of Pseudomonas chlororaphis subsp. auerofaciens B 5326 bacteria and Saccharomyces cerevisiae Y 4317 yeast. Modern methods were employed to assess the microorganisms' metabolites, such as thin-layer chromatography for amino acid composition evaluation and the Salkowski reaction for detecting indole-3-acetic acid in the culture fluid. In the initial stages of the work, it was demonstrated that there was no competitive interaction between bacteria and fungi. The maximum concentration of colony-forming units during the co-cultivation of P. chlororaphis and S. cerevisiae was (3 ± 0.2) × 10^8 and (8 ± 0.2) × 10^6 CFU/ml, respectively. The study revealed that P. chlororaphis and S. cerevisiae could synthesize indole-3-acetic acid during co-cultivation. Experiments with the addition of tryptophan showed that the exogenous introduction of the amino acid stimulates the accumulation of phytohormones in the culture fluid only for P. chlororaphis. Therefore, we hypothesize that S. cerevisiae is the main source of tryptophan during the co-cultivation of microorganisms. The obtained data serve as a basis for creating a complex biological preparation for plant treatment and confirm our hypothesis regarding the possibility of co-cultivating microorganisms belonging to different taxonomic categories.