Department of Biotechnology and Microbiology, Faculty of Sciences and Technology, University of Debrecen, Debrecen, Hungary.
Department of Pathology, Kenézy Gyula County Hospital, Debrecen, Hungary.
J Basic Microbiol. 2018 Nov;58(11):957-967. doi: 10.1002/jobm.201800200. Epub 2018 Aug 31.
The physiological background of the unusually high cadmium tolerance (MIC > 2 mM) of Aspergillus fumigatus Af293 was investigated. The cadmium tolerance of the tested environmental and clinical A. fumigatus strains varied over a wide range (0.25 mM < MIC < 1 mM). Only the Af293 strain showed a MIC value of >2 mM, and this phenotype was accompanied by increased in vivo virulence in mice. A strong correlation was found between the cadmium tolerance and the transcription of the pcaA gene, which encodes a putative cadmium efflux pump. The cadmium tolerance also correlated with the iron tolerance and the extracellular siderophore production of the strains. In addition to these findings, Af293 did not show the synergism between iron toxicity and cadmium toxicity that was detected in the other strains. Based on these results, we suggest that the primary function of PcaA should be acting as a ferrous iron pump and protecting cells from iron overload. Nevertheless, the heterologous expression of pcaA may represent an attractive strain improvement strategy to construct fungal strains for use in biosorption or biomining processes or to prevent accumulation of this toxic metal in crops.
我们研究了烟曲霉 Af293 异常高的镉耐受性（MIC>2mM）的生理背景。测试的环境和临床烟曲霉菌株的镉耐受性差异很大（0.25mM<MIC<1mM）。只有 Af293 菌株表现出 MIC 值>2mM，并且这种表型伴随着体内毒力在小鼠中增加。发现镉耐受性与编码假定镉外排泵的 pcaA 基因的转录之间存在很强的相关性。镉耐受性还与菌株的铁耐受性和细胞外铁载体的产生相关。除了这些发现，Af293 没有表现出其他菌株中检测到的铁毒性和镉毒性之间的协同作用。基于这些结果，我们认为 PcaA 的主要功能应该是作为亚铁泵，防止细胞铁过载。然而，异源表达 pcaA 可能代表一种有吸引力的菌株改良策略，用于构建用于生物吸附或生物采矿过程的真菌菌株，或防止这种有毒金属在作物中的积累。
