Population dynamics of Pseudomonas spp. from the rhizosphere of Leersia hexandra during soil phytoremediation with crude oil in southeastern Mexico

The present study assessed the effectiveness of phytoremediation and natural attenuation in removing total petroleum hydrocarbons (TPH) from clayey soils in the Mexican humid tropics for 12 months under mini-greenhouse conditions. The experiment was performed using a 4 × 2 × 2 factorial design with four crude oil concentrations, two technologies (phytoremediation with Leersia hexandra Swartz and natural attenuation with native microorganisms), and two exposure times (6 and 12 months). The results showed soil microbial respiration increased due to crude oil concentration and exposure time effects; however, crude oil induced population inhibition of Pseudomonas spp. After 12 months of exposure, the rhizosphere of L. hexandra achieved a total of 62.9%, 40.2%, and 33.1% crude oil removal from soils initially containing 30, 60, and 90 g kg⁻¹, whereas natural attenuation achieved 74.8%, 43.7%, and 35.2% removal, respectively. The maximum removal capacity was 30.7 ± 1.3 g kg⁻¹ crude oil for both technologies at 90 g kg⁻¹ crude oil. P. aeruginosa, P. taiwanensis, P. entomophila, P. mosselii, and P. agglomerans were identified in soils with crude oil. These findings highlights the need to integrate biotic and abiotic interactions in the development of bioremediation strategies for tropical soils contaminated with light crude oil.