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Abstract This study assessed heavy metal contamination levels associated with the soils in municipal solid waste landfills and heavy metal accumulation found in plants native to the area. Furthermore, the characterization of new isolates of plant growth promoting rhizobacteria (PGPR) which are resistant to heavy metals was carried out. Results found that in all soil samples tested, cadmium, copper, lead, and zinc could be found. Cadmium had the greatest contamination factor, indicating a very high level of contamination. The cadmium and lead concentrations were highest in the shoots of Urena lobata L., while shoots of Brachiaria mutica Forssk. and Celosia argentea L. contained the greatest copper and zinc concentrations, respectively. There were forty-eight isolates of rhizobacteria, nine of which were resistant to cadmium, copper, and lead. Two of these isolates, designated as Cd3A7 and Cd2ES7, produced elevated levels of indole-3-acetic acid and were identified to be E. cloacae and K. pneumoniae . Both PGPR strains demonstrated the ability to enhance root and shoot growth in Helianthus annuus L. under conditions of heavy metal contamination. They were also found to colonize the interior tissues of the roots as well as the surface of the H. annuus roots. The plants successfully survived in heavy metal-contaminated landfill soil, enhancing the bioavailability of cadmium and lead. In conclusion, these PGPR exhibited characteristics making them candidates for application in heavy metal phytoremediation at landfill sites. Graphical abstract
Montreemuk et al. (Tue,) studied this question.