Ability to produce indole acetic acid is associated with improved phosphate solubilising activity of rhizobacteria

• Published in: Archives of microbiology 2021-09, Vol.203 (7), p.3825-3837
• Main Authors: Alemneh, Anteneh Argaw, Cawthray, Gregory R., Zhou, Yi, Ryder, Maarten H., Denton, Matthew D.
• Format: Article
• Language: English
• Subjects: Acetic acid; Acids; Archives & records; Bacteria; Biochemistry; Biomedical and Life Sciences; Biotechnology; Carboxylates; Cell Biology; Citric acid; Ecology; Genera; Growth media; Indoleacetic acid; Ketoglutaric acid; Life Sciences; Malate; Microbial Ecology; Microbiology; Organic acids; Original Paper; Phosphates; Phosphorus; Phylogeny; Plant growth; Solubilization; Tryptophan
• ISSN: 0302-8933; 1432-072X
• DOI: 10.1007/s00203-021-02364-w

Indole acetic acid (IAA) can upregulate genes encoding enzymes responsible for the synthesis of carboxylates involved in phosphorus (P) solubilisation. Here, we investigated whether IAA and its precursor affect the P-solubilising activity of rhizobacteria. A total of 841 rhizobacteria were obtained using taxonomically selective and enrichment isolation methods. Phylogenetic analysis revealed 15 genera of phosphate solubilising bacteria (PSB) capable of producing a wide range of IAA concentrations between 4.1 and 67.2 µg mL −1 in vitro. Addition of l -tryptophan to growth media improved the P-solubilising activity of PSB that were able to produce IAA greater than 20 µg mL −1 . This effect was connected to the drop of pH and release of a high concentration of carboxylates, comprising α -ketoglutarate, cis -aconitate, citrate, malate and succinate. An increase in production of organic acids rather than IAA production per se appears to result in the improved P solubilisation in PSB.