Abstract
► Thirty metal-resistant bacterial endophytes of Cd-hyperaccumulator
S. nigrum L. were analyzed. ► The genotypic and phenotypic characteristics of these bacterial endophytes were diversiform. ► Several bacteria with multiple PGP traits showing potential in assist phytoremediation.
This study investigates the heavy metal-resistant bacterial endophytes of Cd-hyperaccumulator
Solanum nigrum L. grown on a mine tailing by using cultivation-dependent technique. Thirty Cd-tolerant bacterial endophytes were isolated from roots, stems, and leaves of
S. nigrum L. and classified by amplified ribosomal DNA-restriction analysis into 18 different types. Phylogenetic analysis based on 16S rDNA sequences showed that these isolates belonged to four groups:
Actinobacteria (43%),
Proteobacteria (23%),
Bacteroidetes (27%) and
Firmicutes (7%). All the isolates were then characterized for their plant growth promoting traits as well as their resistances to different heavy metals; and the actual plant growth promotion and colonization ability were also assessed. Four isolates were re-introduced into
S. nigrum L. under Cd stress and resulted in Cd phytotoxicity decrease, as dry weights of roots increased from 55% to 143% and dry weights of above-ground from 64% to 100% compared to the uninoculated ones. The total Cd accumulation of inoculated plants increased from 66% to 135% (roots) and from 22% to 64% (above-ground) compared to the uninoculated ones. Our research suggests that bacterial endophytes are a most promising resource and may be the excellent candidates of bio-inoculants for enhancing the phytoremediation efficiency.