Isolation of cadmium-resistance and siderophore-producing endophytic bacteria and their potential use for soil cadmium remediation

Yanglong Li; Shumeng Wei; Xiangteng Chen; Yuhong Dong; Mansheng Zeng; Chaowu Yan; Lingyu Hou; Ruzhen Jiao

doi:10.1016/j.heliyon.2023.e17661

Isolation of cadmium-resistance and siderophore-producing endophytic bacteria and their potential use for soil cadmium remediation

Heliyon. 2023 Jun 26;9(7):e17661. doi: 10.1016/j.heliyon.2023.e17661. eCollection 2023 Jul.

Authors

Yanglong Li^{1

2

3}, Shumeng Wei^{1

2

3}, Xiangteng Chen^{1

2

3}, Yuhong Dong^{1

2

3}, Mansheng Zeng⁴, Chaowu Yan⁵, Lingyu Hou^{1

2

3}, Ruzhen Jiao^{1

2

3}

Affiliations

¹ Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, China.
² State Key Laboratory of Tree Genetics and Breeding, Chinese Academy of Forestry, Beijing 100091, China.
³ Key Laboratory of Tree Breeding and Cultivation of State Forestry Administration, Chinese Academy of Forestry, Beijing 100091, China.
⁴ Experimental Center of Subtropical Forestry, Chinese Academy of Forestry, Fenyi 336600, China.
⁵ Forestry Bureau of Xinyu City, Jiangxi Province, Xinyu 338000, China.

Abstract

Endophyte-assisted phytoremediation is an emerging technique for soil heavy metals (HMs) remediation and has become a research focus in the world because of the benefits of endophytes on plant growth and uptake of HMs. In this study, multifunctional endophytic bacteria strains were isolated and screened, and the feasibility of these strains for soil cadmium (Cd) remediation was investigated by soil incubation experiments and pot experiments. All endophytic bacteria were isolated from the roots of woody plants grown on Cd-contaminated soil. Seven endophytic bacteria strains had capacities to tolerate Cd toxicity and produce siderophores, and sequence analysis of the 16S rRNA gene classified these strains as belonging to the genera Burkholderia, Pseudomonas, Pantoea, and Herbaspirillum. All strains were able to produce hydroxamate siderophores (32.40%-91.49%) and had three or more plant growth promoting properties such as phosphorus solubilization, nitrogen fixation, indole acetic acid and 1-aminocyclopropane-1-carboxylate deaminase production. They were all strongly resistant to Cd²⁺ toxicity, with the minimum inhibitory concentration in LB medium ranging from 1.5 mM to 9.0 mM. Except for strain Burkholderia contaminans JLS17, other strains showed decreasing removal rates within continuously elevated Cd²⁺ concentration of 10-100 mg L^-1. Compared with the uninoculated treatment, the inoculation of strains B.contaminans JLS17, Pseudomonas lurida JLS32, and Pantoea endophytica JLS50 effectively increased the concentration of acid-soluble Cd and decreased the concentration of reducible, oxidizable, and residual Cd in the soils of different Cd contamination levels. In pot experiments, inoculation of strains JLS17 and YTG72 significantly (p < 0.05) promoted the growth of above-ground parts and root system of slash pine (Pinus elliottii) under Cd stress. This study provides a valuable biological resource for endophyte-assisted phytoremediation and a theoretical basis for the application of endophytic bacteria for remediation of Cd-contaminated soil.

Keywords: Cadmium contamination; Cadmium resistance; Endophyte-assisted phytoremediation; Endophytic bacterium; Plant growth promotion; Siderophore.