Plant growth-promoting effect and its mechanism of the DDT-degrading strain PYR2

Abstract:

[Background] Previous results showed that the DDT-degrading strain, Chryseobacterium sp. PYR2, could efficiently remove DDT and other pollutants from contaminated soil and was great potential in bioremediation. However, the influence of PYR2 on plants and also microorganism-plant interactions is not clear. [Objective] In this study, the plant growth-promoting efficiency and its mechanism of strain PYR2 was investigated, thus providing the theoretical basis for the further development of DDT degradation and plant growth-promoting dual-effect bacterial agents. [Methods] Seed soaking and plant pot experiments were conducted to reveal the plant growth promoting effects of PYR2 on wheat. Salkowski method was used to detect the concentration of indole-3-acetic acid (IAA). Single factor experiments were performed to detail the effects of different culture conditions on its growth and IAA yield. Liquid chromatography-tandem mass spectrometry-multiple reaction monitoring (LC-MS/MS-MRM) detection was employed to detect the intermediate metabolites of IAA biosynthetic process. [Results] Seed germination rates of wheat was greatly enhanced, and so the growth of wheat plants by using cell suspension of PYR2, as the significant increase of height, lateral root number, fresh weight as well as dry weight. The optimum IAA synthesis conditions were temperature 30 °C, pH 7.0?8.0, salt ion concentration <0.5%, L-tryptophan 50 mg/L. The intermediate metabolites of IAA synthesis were tryptophol (TOL), tryptamine (TAM) and indole-3-acetamide (IAM), suggesting that there are three different IAA synthetic pathways in PYR2 (IPyA, TAM and IAM). [Conclusion] Strain PYR2 exhibited significant plant growth promoting effects on wheat, due to its multiple and effective IAA biosynthetic pathways. These results suggest that PYR2 is greatly potential in the bioremediation of and plant-growth in pesticide contaminated soil.