Achromobacter sp. PHED2 enhances the phenanthrene degradation and stress tolerance in maize involving the participation of salicylic acid

Abstract

Phenanthrene (PHE) is harmful to human health and is difficult to be eliminated from environment. In this study, two aerobic bacteria capable of utilizing PHE as a sole source of carbon and energy were isolated and classified as Burkholderia sp. PHED1 and Achromobacter sp. PHED2 according to 16S rDNA analysis. The combined use of maize plants and strain PHED1 or PHED2 enhanced the removal efficiency of PHE (200 mg/kg) from the soil. Moreover, PHED2 inoculation showed more enhancement of root dry weight in comparison with PHED1. PHED2 inoculation also showed more increases of chlorophyll content, net photosynthesis rate and transpiration rate in maize plants in comparison with PHED1. In the PHE degradation pathway by strain PHED2, it was proposed that the salicylic acid (SA) was formed from the 1-hydroxy-2-naphthoic acid, through the intermediate of 1, 2-dihydroxynaphthalene. The SA as the PHE degradation product by PHED2 could enhance the growth of maize plant, increase the reduced form of glutathione content and glutathione reductase activity, which participated in the promotion of PHE degradation and stress tolerance in maize plants. • Strains PHED1 and PHED2 could degrade phenanthrene as a sole carbon source. • Salicylic acid was identified as phenanthrene degradation product by PHED2. • PHED2 enhanced salicylic acid content and stress tolerance in maize. • PHED2 improved the phenanthrene degradation in maize plants.