Physiological background of the remarkably high Cd²⁺ tolerance of the Aspergillus fumigatus Af293 strain

Abstract

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.

Physiological and Transcriptional Responses of Candida parapsilosis to Exogenous Tyrosol

“…and Oligo Analyser (version 1.0.2) software and were purchased from Integrated DNA Technologies. Three parallel measurements were performed with each sample in a LightCycler 480 II real-time PCR instrument (Roche, Switzerland) (40). Relative transcription levels were quantified with the ΔΔCP method using the formula ΔΔCP ϭ ΔCP control Ϫ ΔCP treated , where ΔCP treated ϭ CP tested gene Ϫ CP reference gene , measured from treated cultures, and ΔCP control ϭ CP tested gene Ϫ CP reference gene , measured from control cultures.…”

“…Only data calculated with the ACT1 (CPAR2_201570) transcription values are presented. ΔΔCP values are expressed as means Ϯ SD calculated from three independent measurements, and ΔΔCP values significantly (P Ͻ 0.05) higher or lower than zero were determined using Student's t test (40).…”

Duplications and losses of genes encoding known elements of the stress defence system of the Aspergilli contribute to the evolution of these filamentous fungi but do not directly influence their environmental stress tolerance

“…2017 ). Not surprisingly, the Kruskal-Wallis test did not show any significant difference in the cadmium tolerance among the Aspergillus species possessing two, one or even zero pcaA orthologs ( Kurucz et al. 2018b ).…”

“…2018b ). Moreover, the MIC 50,cd values of 10 A. fumigatus isolates varied within a wide range (0.25 mM–>2 mM) and showed strong positive correlation with the relative transcription of the pcaA gene ( Kurucz et al. 2018b ).…”

Arginine Auxotrophy Affects Siderophore Biosynthesis and Attenuates Virulence of Aspergillus fumigatus

“…It is important to note that the previous study used different genetic backgrounds compared to the current study: deletion of argB was performed in a derivative of A. fumigatus Af293 [19][20][21], which might indicate that the genetic background interferes with the effect of arginine auxotrophy on virulence in the G. mellonella model. In this context, it is interesting to note that several studies revealed significant differences in physiological responses to abiotic stimuli and virulence in murine models of invasive pulmonary aspergillosis between A. fumigatus Af293 and other A. fumigatus isolates including commonly used A. fumigatus CEA10 [44][45][46][47][48]. Sugui et al [47] concluded that Af293 possesses a nutritional deficiency.…”