Histoplasma capsulatum
2014; Linguagem: Inglês
10.1128/9781555816636.ch45
Autores Tópico(s)Peptidase Inhibition and Analysis
ResumoMolecular phylogenetic analyses reveal that Histoplasma capsulatum comprises at least seven distinct phylogenetic groups associated with different geographical locations. Molecular differences between Histoplasma strains have been identified using restriction fragment length polymorphisms (RFLPs) of mitochondrial DNA, ribosomal DNA, and the YPS3 locus. The yeast phase of Histoplasma is the morphological form found in infected tissues and is the phase devoted to pathogenesis. When subjected to a temperature of 37⁰C, germinating Histoplasma conidia or hyphal cells undergo a morphological conversion to produce yeast phase cells. Genetic evidence demonstrating the role of these potential iron acquisition mechanisms during intramacrophage growth of Histoplasma yeast has only been demonstrated for siderophores (SID1). Consistent with its role in pathogenesis, α-glucan is synthesized solely by yeast phase cells; AGS1 is only expressed by Histoplasma in the yeast phase. The molecular details underlying the mechanisms promoting Histoplasma virulence are now beginning to be revealed with the application of molecular genetics. Investigation of geographically overlapping yet nonrecombining species at the genome level should also provide an important perspective on Histoplasma evolution. Genome comparisons with other species may also enhance our understanding of the issue of dimorphism. The virulence factors identified for Histoplasma have all relied upon the development of reverse genetics methodology to functionally demonstrate the role of suspected genes in virulence. The ability of forward genetics to identify novel or unsuspected genes involved in the biology of Histoplasma is now possible through insertional mutagenesis techniques.
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