| 摘要: |
| 【目的】比较2种深色有隔内生真菌（dark septate endophytes，DSE）Phialocephala fortinii和Phaeoacremonium mortoniae对重金属铅（Pb2+）的耐受性及富集能力，初步分析相关的重金属铅耐受性机制，为DSE在重金属污染区土壤治理和植被修复中的应用提供理论依据。 【方法】采用液体摇瓶培养方法，比较不同Pb2+质量浓度（0（对照）,300,600,900,1 200 mg/L）胁迫下P.fortinii和P. mortoniae的生长状况，测定其培养液pH值和有机酸质量浓度，以及菌丝内Pb2+含量、超氧化物歧化酶（SOD）活性和还原型谷胱甘肽（GSH）、丙二醛（MDA）、可溶性蛋白含量的变化，分析其可能的Pb耐受性机制。【结果】当Pb2+质量浓度为0～1 200 mg/L时，2种DSE均有不同程度的生长，P. fortinii的Pb2+半致死浓度（EC50）（951.5 mg/L）显著高于P. mortoniae（431.0 mg/L）（P＜0.05）。随培养液中Pb2+质量浓度的增加，2种DSE菌丝干质量逐渐减小，而菌丝内的Pb2+含量却逐渐升高，P. fortinii的铅富集量逐渐增加，并在Pb2+质量浓度为1 200 mg/L达到最大，而P. mortoniae的铅富集量则是先增加后减少，在Pb2+质量浓度为900 mg/L达到最大。当Pb2+质量浓度为300～1 200 mg/L时，P. fortinii的菌丝干质量和Pb2+富集量均高于P. mortoniae，而菌丝内的Pb2+含量却低于后者。随培养液中Pb2+质量浓度的升高，P. fortinii菌丝的SOD活性和可溶性蛋白含量均先增加后减少，而GSH和MDA含量则逐渐增加，且以上4个指标均在Pb2+质量浓度为600 mg/L时达到最大值；P. mortoniae菌丝内的SOD活性以及GSH、MDA和可溶性蛋白含量均先增加后减少，除SOD活性在Pb2+质量浓度300 mg/L达到最大值外，其他指标均在Pb2+质量浓度为600 mg/L时达到最大值。2种DSE培养液的pH值均随Pb2+质量浓度的升高而下降，从中只检测到草酸和乙酸2种小分子有机酸；2种DSE在供试的Pb2+质量浓度下均能产生草酸，且草酸质量浓度随培养液中Pb2+质量浓度的增加（＞300 mg/L后）而极显著增大，在Pb2+质量浓度为1 200 mg/L时达到最大值（P＜0.01），而2种DSE仅在Pb2+质量浓度较高（600～1 200 mg/L）时产生乙酸；在Pb2+质量浓度为600～1 200 mg/L时，P. fortinii培养液中草酸和乙酸质量浓度都显著高于P. mortoniae（P＜0.05）。【结论】2种DSE对铅都有一定的耐受性和富集能力，其中P. fortinii的耐受性和富集能力明显优于P. mortoniae，SOD活性提高以及GSH、可溶性蛋白和小分子有机酸（草酸和乙酸）的大量积累可能是这2种DSE减轻铅毒害、提高铅耐受性的潜在机制之一。 |
| 关键词: 有隔内生真菌 铅耐受性 有机酸 |
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| 基金项目:国家自然科学基金项目（31300543）；西北农林科技大学基本科研创新一般项目（2452013QN108，2452015343）；西北农林科技大学引进人才科研启动费项目（Z111021204）；陕西省专项配套经费项目 |
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| Lead tolerance of two dark septate endophytes |
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YANG Chao,XIE Qingzhe,CHU Wenhui，et al
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| Abstract: |
| 【Objective】In this study,the lead (Pb) tolerance and enrichment ability of two dark septate endophytes (DSE),Phialocephala fortinii and Phaeoacremonium mortoniae,were compared and the related lead tolerance mechanisms were preliminarily analyzed to provide basis for the application of DSE in heavy metal pollution control and vegetation restoration.【Method】Under liquid culture condition with different Pb2+ mass concentrations (0，300,600,900 and 1 200 mg/L),fungal growth status,pH and organic acids mass concentration in liquid culture medium as well as lead content,superoxide dismutase (SOD) activity,contents of glutathione (GSH),malondialdehyde (MDA) and soluble protein in mycelia were measured and analyzed.The possible mechanisms of lead tolerance were also analyzed and discussed.【Result】 With the Pb2+ concentration of 0-1 200 mg/L,both DSE grew and the semi lethal concentration (EC50) of P. fortinii (951.5 mg/L) was significantly higher (P<0.05) than that of P. mortoniae (431.0 mg/L).With the increase of Pb2+ concentration,the mycelia dry weight of both DSE gradually reduced,while the Pb2+ contents in mycelia increased.The Pb2+ enrichment in P. fortinii increased gradually and reached the maximum at 1 200 mg/L,while the enrichment in P. mortoniae increased firstly and then decreased with the maximum at 900 mg/L.When Pb2+ concentration was 300-1 200 mg/L,the dry weight and lead accumulation of P. fortinii were higher than those of P. mortoniae,but Pb2+ content in mycelia of P.fortinii was lower than that of P. mortoniae.The SOD activity and soluble protein contents in the mycelia of P. fortinii increased firstly and then decreased with the increase of Pb2+ concentration,while GSH and MDA contents gradually increased.All indexes reached the maximum at 600 mg/L.With the increase of Pb2+ concentration,SOD activity and contents of GSH,MDA and soluble protein in mycelia of P. mortoniae increased firstly and then decreased.All reached the maximum at 600 mg/L except SOD activity,which reached the maximum at 300 mg/L.The pH values of two fungal culture media decreased with the increase of Pb2+ concentration,and only oxalic acid and acetic acid were detected.Oxalic acid was detected at all tested concentrations,and its mass concentrations increased significantly with the increase of Pb2+ concentrations (300-1 200 mg/L) with the maximum at 1 200 mg/L.Acetic acid was only detected under high Pb2+ concentration (600-1 200 mg/L).The contents of both oxalic acid and acetic acid in P. fortinii culture medium were significantly higher (P<0.01) than in P. mortoniae at Pb2+ concentration of 600-1 200 mg/L.【Conclusion】Both DSE showed high Pb2+ tolerance and accumulation ability,and P. fortinii was better than P. mortoniae.The increase of SOD activity and accumulation of GSH,soluble protein and small molecule organic acids (oxalic acid and acetic acid) may relate with the high Pb2+ tolerances. |
| Key words: dark septate endophytes lead tolerance organic acids |
