The contribution of endophytic bacteria to Albizia lebbeck-mediated phytoremediation of tannery effluent contaminated soil

ABSTRACT

Toxicity of chromium often impairs the remediation capacity of plants used in phytoremediation of polluted soils. In this study, we have identified Albizia lebbeck as a prospective chromium hyperaccumulator and examined cultivable diversity of endophytes present in chromium-treated and control saplings. High numbers (22–100%) of endophytic bacteria, isolated from root, stem, and leaf tissues, could tolerate elevated (1–3 mM) concentrations of K₂CrO₇. 16S rRNA gene sequence-based phylogenetic analysis showed that the 118 isolates obtained comprised of 17 operational taxonomic units affiliated with the proteobacterial genera Rhizobium (18%), Marinomonas (1%), Pseudomonas (16%), and Xanthomonas (7%) but also with members of Firmicutes genera, such as Bacillus (35%) and Salinococcus (3%). The novel isolates belonging to Salinococcus and Bacillus could tolerate high K₂CrO₇ concentrations (3 mM) and also showed elevated activity of chromate reductase. In addition, majority (%) of the endophytic isolates also showed production of indole-3-acetic acid. Taken together, our results indicate that the innate endophytic bacterial community assists plants in reducing heavy metal toxicity.

KEYWORDS:

• chromium remediation
• phytoremediation
• endophytic bacteria
• chromate reductase
• tannery effluent

Funding

This work was supported by the KU Research Professor Program of Konkuk University, University Grant commission, Government of India and Ministry for School and Sports of the Republic of Slovenia under Slovenian Research Agency program P1-0198.