| The development of industrialization,the practice of improper waste disposal and the usage of chemicals in agriculture accelerated soil contamination worldwide.The most common soil contaminants contained heavy metals,pesticides,hydrocarbons and herbicides.Among these,heavy metals owned a major share due to their mutagenicity,cytotoxicity,and carcinogenic nature.Fungi have a very effective mechanism to uptake heavy metals from environment.Different fungi have distinct enrichment of different heavy metals.Many researches showed that a portion of the edible macrofungi and medicinal macrofungi had different degrees of enrichment for some heavy metals.Therefore,the quality and safety problems of mushrooms caused enough attention of consumers and researchers.The effects of different concentrations of lead ions and manganese ions on the growth of P.adiposa were studied in this article.Mycelia in plate media and liquid media were cultured for 10d and 5d respectively.The morphological characteristics were observed via electron microscopy and the growth characteristics including the form of mycelia and clampconnection were recorded.Content of lead ions and manganese ions in mycelia was also determined by atomic absorption spectrometry.The production of exopolysaccharide by the mycelia in the liquid medie was measured with the method of phenol-sulfuric acid method as to validate the vitality of the mycelia.Bonding mechanism of lead ions and manganese ions in P.adiposa was analyzied and compared with the bonding mechanism of P.ostreatus and Pgeesteranus.There was a significant reduction of clampconnection caused by lead ions and manganese ions in the plate media,while the clampconnection became unevenly distributed with big differences in size.The mycelia appeared rugate and proteiform,suggesting the decrease of the mycelial vitality caused by stresses of lead ions and manganese ions.The colonies were larger than others when the concentrations of lead ions and manganese ions in the plate media was 100 mg/L which also significantly inhibited when the concentration was equal or greater than 500 mg/L.The activity of CAT,POD and SOD of the mycelia under the stress of lead ions was higher than that under the stress of manganese ions in plate media.P.adiposa didn't grow when it was cultured in the media containing 1500 mg/L?3000 mg/L lead ions or manganese ions.When cultured in the plate media with the concentration of 1000 mg/L manganese ions,the maximum accumulation of manganese ions in mycelia was 7.45 mg/g.However,when cultured in the plate media with the concentration of 100 mg/L lead ions,the maximum accumulation of lead ions in mycelia was 1.77 mg/g.For the liquid culture,the fresh weight of mycelia and exopolysaccharide production reached to maximum when lead ions was 50 mg/L,or manganese ions was 300 mg/L.The activity of CAT,POD and SOD of the mycelia under lead ions stress was higher than that under the manganese ions stress.The lead and manganese content in the mycelia increased significantly with the increase of heavy metals concentrations.The mycelia could hyperaccumulate lead ions up to 50.80 mg/g when the concentration of lead ions in the media was 700 mg/L,and the mycelia could hyperaccumulate manganese ions up to 29.80 mg/g when the concentration of manganese ions in the medium was 700 mg/L.Metal ions can be immobilized by functional groups such as amines,carboxyls,hydroxyls,phosphomonoesters and phosphodiesters which are native to the proteins,lipids,and carbohydrates on the cell walls of organisms.In P.adiposa,P.ostreatus and P.geesteranus,high-concentrated lead ions existed mainly in complexing form,and high-concentrated manganese ions existed mainly in both complexing form and simple-bonding form.In the liquid media,the adsorption of lead ions was higher than that of manganese ions.In the plate media,the adsorption of lead ions was higher than that of manganese ions of P.adipose,but the adsorption of manganese ions was higher than that of lead ions of P.ostreatus and P.geesteranus. |
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