Isolation and characterization of robust plant growth-promoting rhizobacteria from lignite mines, Gujarat

Abstract

The objective of the present study was to isolate and characterize plant growth promoting rhizobacteria (PGPR) found in the rhizosphere zone of plants growing in coal mines, Gujarat, India. A total 37 soil samples were collected from the rhizosphere of mined site at Amod G-19 Extension Lignite Mine. The physicochemical analysis was carried out using standard protocols of Agri Biochem Research Lab. The physicochemical analysis of coal mine spoils revealed that the soils were contaminated with heavy metals, had salt stress, and had a variation in pH. The rhizobacteria were isolated from soil samples exhibiting multiple plant growth promoting traits such as nitrogen fixation, phosphate, potash, and zinc-solubilization. Total 89 isolates were selected for further detailed study. The maximum microbial population was found for nitrogen-fixing bacteria (60.67%) followed by phosphate (21.35%), zinc (14.60%), and potash-solubilizing bacteria (3.37%). Isolated PGPR were first assessed for hemolytic activity and isolates showing non-hemolytic activity were further identified by 16S rRNA gene sequencing. Phylogenetic analysis showed that the PGPR belonged to three major phyla: Proteobacteria, Actinobacteria, and Firmicutes. The most represented genera belonged to the Enterobacteriaceae family. The isolated rhizobacterial strains can act as suitable bioinoculants for reclamation of coal mine spoils and to mitigate the abiotic stress conditions in agricultural land.