耐镉棘孢木霉的筛选鉴定及其镉吸附特性研究

Screening and Identification of Cd-Tolerant Trichoderma asperellum and Characterization of Its Cadmium Biosorption

为了筛选鉴定耐镉真菌,采用Cd2+浓度梯度压力驯化法从镉污染稻田土壤中分离到耐镉菌株HD228,综合菌株形态特征、ITS基因序列系统进化分析,鉴定其为棘孢木霉(Trichoderma asperellum)并研究了其镉吸附特性。结果表明:该菌株耐22 mmol/L Cd,对Cd的吸附率可达79.88%;对Pb、Zn、Cu具有很强耐性,Pb、Zn、Cu对HD228的最低抑制浓度(MIC)分别为> 80 mmol/L、> 80 mmol/L、> 30 mmol/L。HD228菌落直径与重金属浓度呈负相关,20 mmol/L时菌落不规则。该菌能在pH值4～8、温度20～35℃条件下良好生长,最适生长和耐镉pH值为5、温度为30℃,温度和pH值均不影响其耐镉能力。其发酵液对水稻出苗、幼苗生长无抑制作用,发酵液40 mL(200 g土)用量对水稻具有促生作用,对镉胁迫水稻具有解毒作用。此耐镉真菌HD228具有应用于镉污染水稻田治理的潜力。

This study aims to screen and identify Cd-tolerant fungus and to characterize its cadmium biosorption.A Cd-tolerant strain(HD228)was isolated from the cadmium polluted paddy soil by using Cd^2+concentration gradient pressure domestication method.Based on its morphological characteristics and the phylogenetic analysis of ITS(internal transcribed spacers)gene sequences,the strain was identified to be Trichoderma asperellum.This strain is resistant to Cd at 22 mmol/L with Cd adsorption rate up to 79.88%,and also resistant to other heavy metals including Pb,Zn and Cu.The MICs(minimum inhibitory concentration)of Pb,Zn and Cu on HD228 are 80 mmol/L,80 mmol/L and 30 mmol/L,respectively.A negative correlation between the colony diameter and the heavy metal concentration was observed,and the colony was out-of-shape when Cd 2+concentration reached 20 mmol/L.The strain HD228 grows well at pH 4 to 8 and the temperature between 20℃and 35℃,and the optimal growth conditions is at pH 5 and 30℃.Neither temperature nor pH value affects its cadmium tolerance.Fermented liquid of this strain has no inhibitory effects on the emergence and growth of rice seedlings,but rather improves the growth of rice seedlings and alleviates the toxicity of cadmium in rice at the ratio of 40 mL to 200 g soil.Thus,the Cd-resistant fungus HD228 has potential for treatment of Cd-polluted rice paddies.