Application of plant growth-promoting endophytes (PGPE) isolated from Solanum nigrum L. for phytoextraction of Cd-polluted soils

Many plant growth-promoting endophytes (PGPE) can assist their host plants cope with contaminant-induced stress responses, which can improve plant growth. In this study, four heavy metals resistant endophytic bacteria, Serratia nematodiphila LRE07, Enterobacter aerogenes LRE17, Enterobacter sp. LSE04 and Acinetobacter sp. LSE06, were isolated from Cd-hyperaccumulator Solanum nigrum L grown in metal-polluted soil. Their plant growth promoting properties such as production of 1-aminocyclopropane-1-carboxylic (ACC) deaminase, indole-3-acetic acid (IAA), siderophores and phosphate solubilizing activity were characterized in vitro. When added to the Cd-amended soils, all of these four bacteria significantly increased Cd extraction from the soils. Subsequently, a pot experiment was conducted to elucidate the effects of inoculating of these PGPE on the plant growth and Cd uptake by S. nigrum L grown in three different levels of Cd-contaminated soils. Results showed that the inoculation with these PGPE not only stimulated the growth of host plant, but also influenced the accumulation of Cd in the root, stem and leaf tissue of S. nigrum L All four strains could colonize the rhizosphere soil and even some can be found in plant interior tissues. The present observations demonstrated that PGPE were valuable microorganism resource which can be exploited to improve the efficiency of phytoextraction. (C) 2010 Elsevier B.V. All rights reserved,