In vitro study of bacterial potentials as biofertilizer and biostimulant agents

Abstract Bacterial biocontrol agents (BCAs) have the potential to promote plant growth by increasing nutrient availability and stimulating hormones to enhance plant health. This study aimed to determine the potential of bacteria as biofertilizers and biostimulants that support plant growth. Ten bacteria of Serratia surfantantfaciens , Brucella intermedia , Bacillus amyloliquefaciens , Bacillus albus , and Burkholderia cepacia were tested for their biofertilizer potential by assessing their ability to solubilize phosphate in Pikovskaya medium, solubilize potassium in Aleksandrov medium, and fix nitrogen in nitrogen-free bromthymol blue (NFB) semi-agar medium. Subsequently, bacteria as biostimulants were evaluated by measuring their production of phytohormones, including indole acetic acid (IAA), gibberellin A3 (GA 3 ), and cytokinins, using High-Performance Liquid Chromatography. Additionally, the bacteria were examined for their effect on seed germination using the ragdoll method by measuring root and shoot lengths and calculating the germination percentage. The results showed that the ten bacteria tested had the potential to produce phytohormones. Three bacteria produce IAA above 8 mg L −1 , while eight produce GA 3 . However, the bacteria produced lower levels of cytokinins (zeatin and kinetin), below 5 mg L −1 . Biofertilizer activity revealed that five bacteria exhibited three activities: phosphate solubilization, potassium solubilization, and nitrogen fixation. Serratia surfactantfaciens , B. intermedia , and B. amyloliquefaciens positively impacted the germination of chilli and kale seeds. These findings suggest that bacterial BCAs have the potential to serve as effective biofertilizers and biostimulants, enhancing their role as plant growth promoters and supporting plant health.