ABSTRACT
Cryptococcus neoformans and C. gattii are pathogenic yeasts that cause life-threatening diseases in humans and animals. Iron is an essential nutrient for virtually every organism as it functions as a cofactor in numerous essential enzymatic reactions. In the literature, the competition for iron between microbes and mammalian hosts during infection is well documented. In this study, we used representational difference analysis (RDA) in order to gain a better understanding of how C. gattii responds to iron starvation. A total of 15 and 29 genes were identified as having altered expression levels due to iron depletion after 3 h and 12 h, respectively. Of these, eight genes were identified in both libraries. The transcripts were related to many biological processes, such as cell cycle, ergosterol metabolism, cell wall organization, transportation, translation, cell respiration and the stress response. These data suggest a remodeling of C. gattii metabolism during conditions of iron deprivation.
Subject(s)
Cryptococcus gattii/genetics , Cryptococcus gattii/metabolism , Gene Expression Profiling , Iron/metabolism , Stress, Physiological , Cryptococcus gattii/physiology , Genes, FungalABSTRACT
Iron, copper, and zinc are essential for all living organisms. Moreover, the homeostasis of these metals is vital to microorganisms during pathogenic interactions with a host. Most pathogens have developed specific mechanisms for the uptake of micronutrients from their hosts in order to counteract the low availability of essential ions in infected tissues. We report here an analysis of genes potentially involved in iron, copper, and zinc uptake and homeostasis in the fungal pathogens Paracoccidioides brasiliensis, Cryptococcus neoformans var. grubii, and Cryptococcus gattii. Although prior studies have identified certain aspects of metal regulation in Cryptococcus species, little is known regarding the regulation of these elements in P. brasiliensis. We also present amino acid sequences analyses of deduced proteins in order to examine possible conserved domains. The genomic data reveals, for the first time, genes associated to iron, copper, and zinc assimilation and homeostasis in P. brasiliensis. Furthermore, analyses of the three fungal species identified homologs to genes associated with high-affinity uptake systems, vacuolar and mitochondrial iron storage, copper uptake and reduction, and zinc assimilation. However, homologs to genes involved in siderophore production were only found in P. brasiliensis. Interestingly, in silico analysis of the genomes of P. brasiliensisPb01, Pb03, and Pb18 revealed significant differences in the presence and/or number of genes involved in metal homeostasis, such as in genes related to iron reduction and oxidation. The broad analyses of the genomes of P. brasiliensis, C. neoformans var. grubii, and C. gattii for genes involved in metal homeostasis provide important groundwork for numerous interesting future areas of investigation that are required in order to validate and explore the function of the identified genes and gene pathways.
ABSTRACT
Cryptococcus neoformans causes the second most common opportunistic infection in patients with AIDS. In Brazil, 4.5% of the AIDS-related opportunistic infections are caused by C. neoformans and all varieties are recognized as etiological agents of cryptococcosis. This pathogen is a ubiquitous environmental yeast, commonly associated with avian excreta and decaying wood, especially Eucalypt species. The aim of the present study was to search for C. neoformans in Eucalypts and analyze the genotypic diversity of the obtained isolates by RAPD and PCR fingerprinting. All obtained isolates have been C. neoformans var. neoformans, serotype D molecular type VNIV. Serotype D, was isolated from 3 (37.5%) out of 8 cities surveyed in the South Brazilian state Rio Grande do Sul. Nine (9%) out of 99 environmental samples were obtained from Eucalypt species, Eucalyptus calmadulensis and Eucalyptus tereticornis. Molecular analysis using RAPD and PCR-fingerprinting revealed very little genetic diversity in the obtained cryptococcal serotype D isolates. To our knowledge this is the first report of the isolation of serotype D from Eucalyptus trees in Brazil. More studies are required in order to establish the ecological significance of this finding.
