Comparison of Two Inoculation Methods of Endophytic Bacteria to Enhance Phytodegradation Efficacy of an Aged Petroleum Hydrocarbons Polluted Soil

Abstract

Endophyte-enhanced phytodegradation is a promising technology to clean up polluted soils. To improve the success rate of this nature-based remediation approach, it is important to advance the inoculation method as this has been shown to strongly affect the final outcome. However, studies evaluating inoculation strategies and their effect on hydrocarbon degradation are limited. This study aims to investigate two different manners of endophyte inoculation in Lolium perenne growing in an aged petroleum hydrocarbon polluted soil: (1) direct soil inoculation (SI), and (2) pre-inoculation of the caryopses followed by soil inoculation (PI). Different endophytic bacterial strains, Rhodococcus erythropolis 5WK and Rhizobium sp. 10WK, were applied individually as well as in combination. Depending on the method of inoculation, the petroleum hydrocarbon (PHC) degradation potential was significantly different. The highest PHC removal was achieved after pre-inoculation of ryegrass caryopses with a consortium of both bacterial strains. Moreover, both strains established in the aged-polluted soil and could also colonize the roots and shoots of L. perenne. Importantly, used endophytes showed the selective colonization of the environment compartments. Our findings show that the method of inoculation determines the efficiency of the phytodegradation process, especially the rate of PHC degradation. This study provides valuable information for choosing the most cost-effective and beneficial means to optimize phytodegradation.

Beneficial traits of root endophytes and rhizobacteria associated with plants growing in phytomanaged soils with mixed trace metal-polycyclic aromatic hydrocarbon contamination

“…Bioaugmentation with PGP and PAH-degrading bacterial strains has been shown to improve dissipation of PAHs in contaminated soils. Recent studies have identified rhizosphere and endophytic bacteria which have the potential to degrade PAH and are widely distributed in the organs and rhizosphere of plants growing in PAH-polluted sites (Baoune et al, 2018;Pawlik et al, 2020). Nevertheless, studies on endophytes or rhizosphere bacteria with PAH degradation capacity are still rare.…”

“…12J1 could efficiently remove pyrene and improve maize and wheat growth in pyrene contaminated soils. Recently, Pawlik et al, (2020) demonstrated that in an aged petroleum hydrocarbon polluted soil, the method of inoculation of endophytic strains determines the efficiency of the phytoremediation process.…”

“…Selection of PAH degraders with metal tolerance and surfactant production abilities, or combining PAH degraders with biosurfactant producers, is of particular interest since surfactants enhance the contaminant solubility . Endophytic bacteria can be a great option as bioinoculants because they have the advantage of proliferating in plant tissue, thus facing less competition for nutrients and being protected from the high stress environments of polluted soils (Pawlik et al, 2020).…”

Root exudate glycine synergistically promotes phytoremediation of petroleum-contaminated soil

“…Existing studies confirm that various types of plants including legumes and grasses are successful in removing organic soil pollutants (Asghar et al, 2017). PHs levels in various soils planted with ryegrass were significantly reduced-up to 20% of the initial PHs concentration (Pawlik et al, 2020). Vitiveria Zizanioides L. effectively removing polycyclic aromatic hydrocarbons (PAHs) and diesel oil from contaminated sediments in India and Pakistan (Nisa et al, 2015).…”

Isolation, Biochemical and Genomic Characterization of Glyphosate Tolerant Bacteria to Perform Microbe-Assisted Phytoremediation

“…Cp3-mCherry was demonstrated to colonize the root cortex cells and xylem vessels of the stem of Crotalaria pumila under metal stress ( Sánchez-López et al, 2018 ). In another study conducted by Pawlik et al (2020) , Lolium perenne was inoculated with the GFP-tagged Rhizobium sp. 5WK collected from an aged petroleum hydrocarbon polluted soil to confirm the endophytic nature of the strain colonization capabilities.…”