XI International Meeting on Paracoccidioidomycosis

XI International Meeting on Paracoccidioidomycosis

Resume:21-1

Poster (Painel)

21-1	SIDEROPHORE PRODUCTION BY Paracoccidioides brasiliensis
Authors:	Mirelle Garcia Silva (UFG - Universidade Federal de Goiás) ; Elisa Flávia Luiz Cardoso Bailão (UFG - Universidade Federal de Goiás) ; Gregory M. Gauthier (UW - University of Wisconsin) ; T. Tristan Brandhorst (UW - University of Wisconsin) ; Alexandre Melo Bailão (UFG - Universidade Federal de Goiás) ; Célia Maria de Almeida Soares (UFG - Universidade Federal de Goiás)

Abstract

Iron is an essential nutrient for all eukaryotes and nearly all prokaryotes. Most of pathogens, such as fungi, have specific mechanisms for iron uptake from their hosts, in which the availability of this ion is extremely low. Low-affinity systems of iron uptake are activated when iron is abundant, whereas high-affinity systems are important under iron-limiting conditions. The siderophore-mediated iron uptake is a type of non-reductive high-affinity system. Siderophores are high-affinity ferric-ion specific chelators with low-molecular weight. Their biosynthesis is controlled by iron availability. These molecules are secreted to mobilize extracellular iron or are produced intracellularly for iron storage. The goal of this work is to investigate the siderophore-mediated iron uptake in Paracoccidioides brasiliensis, the etiologic agent of Paracoccidiodomycosis. An in silico screening at P. brasiliensis isolates structural genomes (01, 03 and 18)was performed in order to identify genes related to iron uptake by the non-reductive pathway. The expression of identified orthologue genes was verified in both iron depleted and iron replete conditions. The overlaid-chrome azurol S (O-CAS) assay and CAS liquid assay were employed, respectively, to detect and quantify the siderophores produced by some P. brasiliensis isolates. Reverse-phase HPLC was used in the identification of siderophores produced by P. brasiliensis. The in silico analysis revealed genes related to siderophore biosynthesis and transport. The expression of the siderophore biosynthesis gene sidA and siderophore transport gene sit1 decreased in iron replete conditions, suggesting that their expression is regulated by iron availability. The O-CAS assay revealed that four P. brasiliensis isolates (Pb01, Pb18, Pb02 and PbEpm83) are hydroxamate producers. The amount of siderophore produced by P. brasiliensis was higher in iron depleted medium, indicating that these molecules play role in the high-affinity iron uptake, as described. The reverse-phase HPLC analysis revealed that dimerum acid is the hydroxamate produced by P. brasiliensis 18. As the limitation of iron availability is a defense strategy of many hosts, the siderophore non-reductive pathway iron acquisition system could be a virulence factor of P. brasiliensis.

Keyword: CAS, hydroxamate, iron uptake, reverse-phase HPLC

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