Bacillus species, due to their soil amendment properties, are important members of plant-growth–promoting rhizobacteria (PGPR). In this study, with the aim to discover potential biofertilizers, 440 Bacillus isolates from different sources were screened qualitatively for phosphate solubilizing and positive isolates were processed for quantitative estimation of solubilized phosphate and organic acid production. | Turkish Journal of Botany Turk J Bot (2018) 42: 183-196 © TÜBİTAK doi: Research Article Plant growth promoting properties of phosphate solubilizing Bacillus species isolated from the Aegean Region of Turkey 1, 1 2 3 Pınar SÖZER BAHADIR *, Fakhra LIAQAT , Rengin ELTEM Ege University Central Research Test and Analysis Laboratories Research and Application Center (EGE MATAL), İzmir, Turkey 2 Graduate School of Natural and Applied Sciences, Department of Biotechnology, Ege University, İzmir, Turkey 3 Department of Bioengineering, Faculty of Engineering, Ege University, İzmir, Turkey Received: Accepted/Published Online: Final Version: Abstract: Bacillus species, due to their soil amendment properties, are important members of plant-growth–promoting rhizobacteria (PGPR). In this study, with the aim to discover potential biofertilizers, 440 Bacillus isolates from different sources were screened qualitatively for phosphate solubilizing and positive isolates were processed for quantitative estimation of solubilized phosphate and organic acid production. Organic acid production was initially detected by pH change of the media, whereas further confirmation and quantitative estimation were done by gas chromatography (GC). The results indicate that phosphate solubilization ranges from ± to ± µg mL–1 for Bacillus isolates and most of the isolates were able to produce more than one organic acid in substantial quantities range between ± and ± (ng µL–1). Correlations among total organic acid concentration, final pH of the media, and soluble phosphate were statistically calculated. The six best phosphate-solubilizing isolates were further tested for indole-3-acetic acid (IAA) production, molecular identification, in vitro seed germination, and pot trials. All six strains produced IAA, significantly enhanced radicle and hypocotyl development,
