Heavy metal (HM) contamination represents a significant threat to soil functionality and ecosystem health. The present study aims to assess the efficacy of an integrated bioremediation strategy combining Lavandula angustifolia (lavender) and a four-strain bacterial consortium in restoring a multi-contaminated soil collected from a former industrial site in Southern Italy. Microcosm experiments were conducted over a period of 90 days, including three treatments and a control: a planted condition (PLANT), a bioaugmented condition (BIOAUG), and a combined plant and bioaugmentation condition (PLANT+BIOAUG). The control (HCS) consisted of unplanted and non-bioaugmented soil. Soil physico-chemical parameters (e.g., pH, electrical conductivity, and heavy metal concentrations), plant growth, microbial abundance, and dehydrogenase activity (DHA) were measured at the initial and final experimental time. Finally, a Soil Quality Index (SQI) was applied. The combined treatment (PLANT+BIOAUG) promoted a significant reduction in total Pb and Sn concentrations by 44.7% and 66.9%, respectively. Moreover, a significant increase in soil pH and microbial abundance was observed. Applying the SQI to integrate overall soil data made it possible to highlight the highest quality score (0.73) for this condition. These findings suggest the potential effectiveness of lavender-assisted bioaugmentation as a scalable and multifunctional strategy for remediating heavy metal-contaminated soils, in line with ecological restoration principles.

This research aimed to characterise hydrocarbonoclastic bacteria isolated from naturally hydrocarbon-contaminated springs and the surrounding soils in the Agri Valley (Southern Italy) and to assess the effectiveness of bioaugmentation using a four-strain microbial consortium for removing hydrocarbons from artificially diesel-contaminated lake waters in mesocosm experiments. Four novel bacterial strains were selected for the experimentation: Gordonia amicalis S2S5, Rhodococcus erythropolis S2W2, Acinetobacter tibetensis S2S8, and Acinetobacter puyangensis S1W1. The four isolates can use diesel oil as their sole carbon source, and some exhibited a relatively high emulsifying capacity and ability to adhere to hydrocarbons. Furthermore, genome analyses revealed the presence of genes associated with the degradation, detoxification, and transport of various contaminants. Mesocosm experiments demonstrated that the bioaugmentation enhanced the capacities of the native lake microbial communities to remove hydrocarbons, although drastic changes in their composition (analysed through Next-Generation Sequencing—NGS) were observed. Taken together, these results suggest that naturally contaminated environments can serve as a valuable reservoir of microorganisms with significant biotechnological potential, particularly in the field of bioremediation. However, a complete understanding of the ability of the isolated bacterial strains to efficiently degrade contaminants requires further research to fully assess their capabilities and limitations across different settings.