Asian Soil Research Journal

Aim: Coal mining leads to the degradation of surface soil’s physical, chemical and microbiological properties. However, functional microorganisms (such as plant growth promoting microorganisms) with the potential to produce phytohormones, fix nitrogen, solubilize phosphate, and others, can be effective in restoring coal mine soils (CMS). This study was conducted to explore the plant growth promoting potentials [indole-3-acetic acid (IAA) production and phosphate solubilization] of bacteria isolated from the abandoned Ogbete coal mine, Enugu State, Nigeria.

Study Design: A laboratory study to isolate bacteria from the coal mine soil, screen bacterial isolates for plant growth promoting traits (IAA production and phosphate solubilization), and identify the isolates that tested positive for the traits using 16S rRNA gene sequencing.

Place and Duration of Study: Nucleometrix Laboratory, Yenegoa, Bayelsa State Nigeria, between June 2025 and August 2025.

Methodology: CMS was analyzed for its physico-chemical properties. Isolation and enumeration of bacterial isolates from the CMS were done on Nutrient agar, after which the bacteria obtained were screened for IAA production and phosphate solubilization following standard methods. Bacterium that tested positive for the trait (potential) was identified using 16S rRNA gene sequencing.

Results: The coal mine soil was acidic (pH 5.84), while Total organic carbon (1.31%), Soil organic matter (2.27%), Total Nitrogen (3.89 mg/kg), Total phosphorus (1.04 mg/kg), were below levels required for arable soils. Total heterotrophic bacteria counts (3.5 × 10⁵ CFU/g) of the CMS were below requirement for arable soils. A total of seven (7) bacterial isolates were recovered from the coal mine soil, out of which one (1) isolate was positive for IAA production, but negative for phosphate solubilization. The other 6 isolates were negative for both IAA production and phosphate solubilization. The IAA producing bacterium was identified using 16S rRNA sequencing as Chryseobacterium indologenes.

Conclusion: This study revealed the IAA producing potential of Chryseobacterium indologenes, which could further be exploited for its potential to biorestore coal mine soil and other disturbed soil ecosystems for future agricultural purpose.This study contributes to the United Nations Sustainable Development Goal 15, targeted at restoring and promoting conservation and sustainable use of terrestrial ecosystems.