Effect of Phosphate-Solubilizing Bacteria on the Mobility of Insoluble Cadmium and Metabolic Analysis.

Ping Yang,Ting Zhou,Bao-Yan He,Zi-Yi Zhao,Xue-Fang Zhou,Li-Li Wang,Yu-Kun Chen,Qu-Sheng Li

doi:10.3390/ijerph15071330

Abstract

Phosphate-solubilizing bacteria (PSB) can promote plant growth by dissolving insoluble phosphate. Therefore, PSB may have the potential to improve the mobility of heavy metals in soils and enhance phytoextraction. This study isolated a few PSB strains that could dissolve CdCO3 and solid Cd in soil. Two typical PSB, namely, high- and low-Cd-mobilizing PSB (Pseudomonas fluorescens gim-3 and Bacillus cereus qh-35, respectively), were selected to analyze the metabolic profiles, metabolic pathways, and mechanisms of mobilization of insoluble Cd. A total of 34 metabolites secreted by the two PSB strains were identified. Gluconic acid was the main contributor to Cd dissolution (42.4%) in high-Cd-mobilizing PSB. By contrast, gluconic acid was not secreted in low-Cd-mobilizing PSB. Metabolic pathway analysis showed that gluconic acid was produced by the peripheral direct oxidation pathway. Hence, PSB with peripheral direct oxidation pathway were likely to have high-Cd-mobilizing capacity.

Highlights

Cadmium or cadmium compounds can increase the risk of lung cancer, kidney lesions, and bone damage [1,2,3,4]
After the strains were incubated in the liquid medium for 1 and 7 days, the fraction of dissolved Cd increased from 9.4% to 92%
P. fluorescens was superior to B. cereus in solubilizing Cd

Summary

Introduction

Cadmium or cadmium compounds can increase the risk of lung cancer, kidney lesions, and bone damage [1,2,3,4]. Phytoextraction is an ecologically friendly and cost-effective technique that can be used to remove Cd from contaminated soils [5,6,7,8] This process suffers from some limitations, such as the low mobility of the tightly bound fraction of Cd in soils with neutral pH, resulting in reduced uptake by plants [9]. To address such limitations, scientists have developed bacterium-assisted phytoextraction, in which bacteria are added to soil to facilitate Cd phytoextraction [10,11,12,13,14]. Bacteria such as Bacillus pumilus E2S2 increased Sedum plumbizincicola Cd uptake (43%) [15], and Pseudomonas sp

Methods

Results

Conclusion