Bioaugmentation of trace element tolerant bacteria as phytostabilization improvement of polluted military soil

SARAN ANABEL; IMPERATO, VALERIA; FERNANDEZ, LUCIA; MERINI, LUCIANO JOSE; VANGRONSVELD, JACO; THIJS, SOFIE

Changsha

Congreso; International Phytotechnologies Conference; 2019

International Phytotechnology Society

The presence of trace elements in polluted soils and their uptake by plants at concentrations that become harmful for humans is of great concern. Bioaugmentation with plant growth promoting (PGP)-bacteria is a low cost and effective strategy used to reduce element uptake by plants and enhance plant survival in this kind of chronically polluted areas. We isolated and characterized trace element (Pb and Cd)-tolerant bacteria to develop inoculants capable of enhancing plant growth and increasing phytostabilization efficiency in polluted military soils. One hundred and five rhizoplane and endophytic trace elements-tolerant bacteria that belong to eight different genera were isolated from Helianthus petiolaris, a pioneer plant species producing aromatic compounds, growing in a Pb and Cd polluted soil. Most of these strains showed multiple PGP capabilities, promoted seed germination, and were able to sequestrate metal in cell biomass when grown in liquid culture. Bacillus paramycoides, Brevibacterium frigotolerans, Bacillus wiedmannii, Cellulosimicrobium cellulans, Methylobacterium sp. and Bacillus proteolyticus were selected to perform bioaugmentation. After two months in the greenhouse, seedlings of sunflower (H. annuus) inoculated with B. proteolyticus developed 40% more biomass compared to the control and decreased 20% Pb and 40% Cd bioaccumulation in shoots. However, B. paramycoides increased tree times Pb and six times Cd accumulation factors without affect plant biomass. Complementary studies on rhizosphere competence were performed by scanning electron microscopy (SEM) and molecular methods involving PCR amplification of the ribosomal intergenic spacer region (ARISA). Our results indicate that bacteria isolated from plants growing in polluted soils can express multiple PGP capabilities in vitro and are able to recolonize plants from the same family. However, only a few strains are able to improve sunflower growth and lower uptake of trace elements from weathered military soils.