Characterization of Endophytic Bacteria Isolated from Typha latifolia and Their Effect in Plants Exposed to Either Pb or Cd

Abstract

Plant-associated bacteria in heavy-metal-contaminated environments could be a biotechnological tool to improve plant growth. The present work aimed to isolate lead- and cadmium-tolerant endophytic bacteria from the roots of <i>Typha latifolia</i> growing in a site contaminated with these heavy metals. Endophytic bacteria were characterized according to Pb and Cd tolerance, plant-growth-promoting rhizobacteria activities, and their effect on <i>T. latifolia</i> seedlings exposed and non-exposed to Pb and Cd. Pb-tolerant isolates were identified as <i>Pseudomonas azotoformans</i> JEP3, <i>P. fluorescens</i> JEP8, and <i>P. gessardii</i> JEP33, while Cd-tolerant bacteria were identified as <i>P. veronii</i> JEC8, JEC9, and JEC11. They all exert biochemical activities, including indole acetic acid synthesis, siderophore production, and phosphate solubilization. Plant-bacteria interaction assays showed that <i>P. azotoformans</i> JEP3, <i>P. fluorescens</i> JEP8, <i>P. gessardii</i> JEP33, and <i>P. veronii</i> JEC8, JEC9, JEC11 promote the growth of <i>T. latifolia</i> seedlings by increasing the root and shoot length, while in plants exposed to either 5 mg/L of Pb or 10 mg/L of Cd, all bacterial isolates increased the shoot length and the number of roots per plant, suggesting that they are plant-growth-promoting rhizobacteria that could contribute to <i>T. latifolia</i> adaptation to the heavy metal polluted site.