How Serratia marcescens HB-4 absorbs cadmium and its implication on phytoremediation

• Published in: Ecotoxicology and environmental safety 2019-12, Vol.185, p.109723, Article 109723
• Main Authors: Chen, Yakui, Zhu, Qifa, Dong, Xiangzhou, Huang, Weiwei, Du, Chenyu, Lu, Diannan
• Format: Article
• Language: English
• Subjects: Adsorption; Bacterial Proteins - metabolism; Binding protein; Biodegradation, Environmental; Bioremediation; Cadmium - analysis; Cadmium - metabolism; Chelating Agents; China; Extracellular adsorption; Houttuynia - chemistry; Intracellular absorption; Microorganism; Periplasm accumulation; Protein Binding; Serratia marcescens - metabolism; Soil Microbiology; Soil Pollutants - analysis; Soil Pollutants - metabolism
• ISSN: 0147-6513; 1090-2414
• DOI: 10.1016/j.ecoenv.2019.109723

A novel strain Serratia marcescens HB-4 with high Cadmium adsorption capacity was isolated from heavy metal contaminated soil in Hunan province, China. S. marcescens HB-4 reduced the concentration of Cd present in wastewater to less than 0.1 mg/L when the inlet stream contained no higher than 5.0 mg/L Cd. After treatment, wastewater meets Integrated Wastewater Discharge Standard of China (GB8978-1996). The naturally dead S. marcescens HB-4 still maintained over 80% of its Cd adsorption capacity. Scanning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive spectroscopy (EDS) results suggested that the mechanism of Cd adsorption can be explained as the synergy of extracellular adsorption, periplasm accumulation and intracellular absorption. The size of the accumulated Cd particular is at the nanometer scale, which can be washed out by EDTA without damaging cell integrity. SDS-polyacrylamide gel electrophoresis experiment showed that the heavy metal binding protein (especially Fe binding protein), transporter, amino acid and histidine periplasmic binding proteins and oxidoreductases were responsible for Cd removal. The pot experiment of S. marcescens HB-4 combined with Houttuynia cordata to detoxify Cd contaminated soil showed that the cadmium content in the aboveground and underground parts of Houttuynia cordata increased by 34.48% and 59.13% (w/w), respectively. The cadmium accumulation in Houttuynia cordata increased by 44.27% compared with the blank group which was not combined with S. marcescens HB-4. This work demonstrates that microbial synergistic phytoremediation has a significant potential to treat heavy metal contaminated soil. [Display omitted] •S. marcescens HB-4 shows an adsorption capacity over 90 mg Cd/g dry cell.•Cd particle was distributed in the periplasmic layer, intracellular and cell surface.•Adsorption, periplasm accumulation & absorption were involved in Cd removal.•Responsible proteins in S. marcescens HB-4 for Cd removal were identified.