Beneficial bacteria associated with Mimosa pudica and potential to sustain plant growth-promoting traits under heavy metals stress

Abstract

The study was carried out to isolate and screen indigenous rhizobacteria associated with Mimosa pudica in ex-tin mining soil with the potential to sustain plant growth-promoting (PGP) traits under heavy metals (HM) stress condition. A total of 58 bacterial strains were isolated, screened for HM (As, Pb and Cd) tolerance and for various PGP traits. Production of PGP substances by selected isolates under influence of HM was further evaluated. The results revealed 5 isolates as HM tolerant (2M1, 3M1 and 3M3 as Pb tolerant; 3M3 and 4M9 as Cd tolerant while 6M2 as As tolerant) and possessing all tested PGP traits. The isolates were identified based on 16S rRNA as Bacillus cereus 2M1, Bacillus cereus 3M1, Bacillus pseudomycoides 3M3, Enterobacter tabaci 4M9 and Pseudomonas plecoglossicida 6M2. Tested isolates sustained PGP traits and withstand high HM stress conditions, particularly isolates 6M2 Pseudomonas plecoglossicida, 4M9 Enterobacter tabaci and 2M1 Bacillus cereus (6M2 had the overall best performance compared to other isolates). The strains are therefore expected to be the major contributing factors for survival of Mimosa pudica which were endemic in the abandoned mining sites and provide basis for using indigenous bacteria for bioremediation of HM contaminated soils.