Effects of two plant growth-promoting rhizobacteria containing 1-aminocyclopropane-1-carboxylate deaminase on oat growth in petroleum-contaminated soil

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Petroleum is potentially toxic to living organisms, and there are worldwide efforts to develop methods for bioremediation of petroleum-contaminated soils. Phytoremediation is an effective method to reduce the concentration of petroleum in soils, and plant growth-promoting rhizobacteria (PGPR) play an important role in the phytoremediation. Two PGPR, Pseudomonas aeruginosa SLC-2 and Serratia marcescens BC-3, were isolated from the rhizophere of Echinochloa grown in petroleum-contaminated soil. These isolates showed capacities for 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, indole acetic acid production, siderophore synthesis, and the degradation of petroleum. The ACC deaminase activity of SLC-2 and BC-3 was 2.52 ± 0.03 μmol α-KA (mg Pr·h)−1 and 38.52 ± 0.37 μmol α-KA (mg Pr·h)−1, respectively. On the other hand, when the concentration of l-Trp increased, the IAA synthesis of BC-3 also increased, while the synthesis of SLC-2 did not change significantly. The ability of synthesized siderophore of SLC-2 was much higher than that of BC-3. The petroleum degradations of SLC-2 and BC-3 increased 4.78 and 7.36 %, respectively. The pot experiment of oat was performed to evaluate the plant growth-promoting abilities of SLC-2 and BC-3. Compared with non-inoculated controls, the height and fresh weight of stems increased (23.64 and 42.57) % and (16.98 and 28.3) %, respectively, whereas the length and fresh weight of roots also increased (10.34 and 20.84) and (24.13 and 43.11) %, respectively, when inoculated with SLC-2 and BC-3. The results indicated that P. aeruginosa SLC-2 and S. marcescens BC-3 can serve as promising microbes for increasing plant growth in petroleum-contaminated soil to improve the phytoremediation efficiency.