镉污染水土中抗镉菌株的筛选鉴定及功能特性

Screening, identification, and functional characterization of cadmium-tolerant bacteria in cadmium-polluted soil and water

摘要:

【背景】 重金属镉污染已经严重威胁到人类赖以生存的环境和生命安全。目前镉污染修复中微生物修复因其具有修复安全、简便、有效、成本低、环境友好等特点而具有更好的应用潜力。【目的】 从镉污染水土中筛选抗镉微生物，为镉污染治理提供更佳的优势菌株。【方法】 采用梯度稀释法和平板划线法从镉污染水土中筛选分离出128株抗镉菌株，采用16S rRNA基因测序技术结合不同微生物的抗镉能力及遗传稳定性，筛选到1株高抗镉菌株HGX-24，对其生物学特性及抗镉性能进行分析，并通过傅里叶变换红外光谱(fourier transform infrared spectroscopy, FTIR)、扫描电子显微镜-能量色散谱仪(scanning electron microscope-energy dispersive spectrometer, SEM-EDS)、胞外蛋白质和多糖含量测定等方法初步探究了菌株HGX-24在镉胁迫下的响应机制，并通过植物盆栽试验探究了菌株HGX-24在修复镉污染中的实际应用效果。【结果】 筛选分离的菌株HGX-24与已报道菌株的相似性≤97.0%，为金黄杆菌属(Chryseobacterium)，该菌株的最高抗镉浓度为350 mg/L，遗传性能稳定，可通过分泌胞外可溶性蛋白及结合菌体表面官能团对镉进行吸附，并能有效缓解镉胁迫下玉米植株的氧化应激。【结论】 抗镉菌株HGX-24具有较好的水土镉污染治理潜力，在镉污染农田修复中发挥菌种优势。

关键词:水土镉污染;抗镉菌株;分离鉴定;抗镉机制

Abstract:

[Background] Cadmium pollution has seriously threatened the environment and life safety of human beings. In recent years, microbial remediation has demonstrated great application potential due to its high safety, simple operation, effectiveness, low costs, and environmental friendliness. [Objective] To screen cadmium-tolerant microorganisms from cadmium-polluted soil and water and provide elite strains for the remediation of cadmium-polluted environments. [Methods] A total of 128 strains exhibiting tolerance to cadmium were isolated and identified from cadmium-polluted soil and water by gradient dilution and plate streaking methods. A highly cadmium-tolerant strain HGX-24 was successfully screened by 16S rRNA gene sequencing combined with the cadmium tolerance and genetic stability assays. The biological characteristics and cadmium tolerance properties of this strain were analyzed. Fourier transform infrared spectroscopy (FTIR), scanning electron microscope-energy dispersive spectrometer (SEM-EDS), and quantification of extracellular polysaccharides and proteins were employed to gain insights into the cadmium tolerance mechanism of HGX-24. Pot experiments were conducted to explore the application effect of HGX-24 in the remediation of cadmium pollution. [Results] The comparative genomic analysis revealed that the homology between the isolated strain HGX-24 and previously reported strains was below 97.0%, identifying HGX-24 as a strain of Chryseobacterium. This strain demonstrated exceptional cadmium tolerance, being capable of tolerating 350 mg/L cadmium and exhibiting genetic stability. It can adsorb cadmium through the secretion of extracellular soluble proteins and binding to chemical functional groups present on the bacterial surface. Moreover, it could alleviate the oxidative stress of maize under cadmium stress. [Conclusion] The cadmium-tolerant strain HGX-24 exhibits considerable potential for the remediation of cadmium-polluted soil and water and gives full play to the advantages of bacteria in the remediation of cadmium-polluted farmland.

Key words:cadmium pollution of soil and water;cadmium-tolerant strains;isolation and identification;cadmium tolerance mechanism