Screening bacterial phosphate solubilization with bulk-tricalcium phosphate and hydroxyapatite nanoparticles.

Area of Science:

• Microbiology
• Soil Science
• Biotechnology

Background:

• Phosphate-solubilizing bacteria (PSB) enhance soil and plant health by releasing phosphorus (P) from insoluble minerals.
• Limited research exists on PSB's ability to solubilize nanosized P materials, such as hydroxyapatite nanoparticles (HANP).
• Understanding PSB interactions with nano-P fertilizers is crucial for developing novel agricultural solutions.

Purpose of the Study:

• To screen and identify phosphate-solubilizing bacteria capable of utilizing bulk and nanosized P sources.
• To evaluate the kinetics of phosphate solubilization and organic acid production by selected bacterial strains.
• To assess the potential of Enterobacter cloacae CP 31 and HANP in agricultural applications.

Main Methods:

• Screening of 43 bacterial strains from vanilla rhizospheres for phosphate solubilization using Ca3(PO4)2, rock phosphate (RP), and HANP.
• Kinetics experiments conducted over 5, 10, and 20 days post-inoculation to measure bacterial biomass, pH reduction, and soluble P concentration.
• Identification of organic acids produced by the bacteria, with a focus on citric acid.

Main Results:

• Bacterial biomass production was similar across experiments, with the lowest biomass observed at 20 days.
• All tested bacteria reduced culture medium pH, correlating with phosphate solubilization via organic acid production (citric acid).
• Enterobacter cloacae CP 31 demonstrated superior performance, achieving the lowest pH (3.7) and highest soluble P (536 mg L-1) with HANP at 10 days.

Conclusions:

• Enterobacter cloacae CP 31 exhibits significant potential as a plant growth-promoting inoculant and for solubilizing nano-P fertilizers.
• The study highlights the efficacy of PSB in solubilizing nanosized hydroxyapatite nanoparticles (HANP).
• Further research is recommended to test Enterobacter cloacae CP 31 as an inoculant in plant studies.