Isolation and characterization of plant growth promoting bacteria (PGPB) from Larrea divaricata Cav., with potential use in phytoremediation of mining soils

Soil contamination with heavy metals is an environmental problem that negatively impacts human health and agriculture. An alternative to mitigate this situation is the use of biological soil decontamination technologies, among which phytoremediation stands out. This process can be enhanced with the use of microorganisms adapted to the environmental conditions to be remedied and capable of stimulating plant growth through various mechanisms. This study aimed to characterize rhizosphere and endophytic bacteria, isolated from roots of Larrea divaricata plant previously irrigated with 100 mg/kg of Pb, 10 mg/kg of Cd, and 400 mg/kg of Zn, in terms of resistance to heavy metals and plant growth promoting (PGP) traits. Twelve isolates were selected based on their resistance and adaptability to these conditions. Next, their properties and capacities to promote plant growth were analyzed. In addition, biofilm production and acyl homoserine lactone molecules (AHLs) were determined, which allows for inferring possible interactions between bacteria and plant-microorganism. Of all, 67% of the selected isolates belong to the genus Bacillus, and to a lesser extent Rhizobium, Rhodopseudomonas, and Agrobacterium. All the strains showed the capacity to produce biofilm, siderophores, and deaminase activity (ACC), in different proportions, while only one showed the capacity to solubilize phosphates. On the other hand, none of the microorganisms showed the production of AHLs against the biosensors used. The results obtained contribute to the development of biotechnological strategies for the formulation of agro-inputs that optimize and/or improve the productivity of the phytoremediation process in an agroecological context.