Screening of multi-metal tolerant plant growth promoting bacteria (PGPB) <i>Stutzerimonas stutzeri</i> WA4 and its assistance on phytoextraction of heavy metals (Cu, Ag and Pb)

In the current study, coal fly ash contaminated soil was collected in and around Mettur Thermal Power Station, Salem district, Tamil Nadu. The metal concentrations present in the coal fly ash soil samples were analyzed and also used for the isolation of bacteria. The isolates were screened for their multi-metal resistance against three heavy metals (Cu, Ag and Pb) and plant growth-promoting traits (siderophore, phosphate solubilization, IAA, cellulase, HCN, and ammonia production). Among the 12 isolates, the WA4 strain revealed promising results for both metal-resistant and plant growth-promoting activity. In the <i>in vitro</i> pot experiment, <i>Spinacia oleracea</i> (Palak), <i>Red amaranth</i> (Red spinach), <i>Capsicum annum</i> (Green chilly) and <i>Solanum melongena</i> (Brinjal) plants were grown in ash-contaminated soil treated with different concentrations of selected bacterial inoculum (25%, 50%, 75% and 100%) along with a control pot. The results of the study indicated that the ash-contaminated soil treated with bacterial inoculum distinctly increased the growth of plants when compared to untreated soil (control). Thus, the best-performing strain WA4 could be utilized as a good bio-stimulant for promoting the growth of selected plants in the re-vegetation programs of ash-contaminated soil.