Understanding Mucor circinelloides pathogenesis by comparative genomics and phenotypical studies

Abstract

The increasing number of infections by species of Mucorales and their high mortality constitute an important concern for public health. This study aims to decipher the genetic basis of Mucor circinelloides pathogenicity, which displays virulence in a strain dependent manner. Assuming that genetic differences between strains may be linked to different pathotypes, we have conducted a study to explore genes responsible for virulence in M. circinelloides by whole genome sequencing of the avirulent strain NRRL3631 and comparison with the virulent strain CBS277.49. This genome analysis revealed 773 truncated, discontiguous and absent genes in the NRRL3631 strain. We also examined phenotypic traits resulting in reduced heat stress tolerance, chitosan content and lower susceptibility to toxic compounds (calcofluor white and sodium dodecyl sulphate) in the virulent strain, suggesting the influence of cell wall on pathogenesis. Based on these results, we focused on studying extracellular protein-coding genes by gene deletion and further pathotype characterization of mutants in murine models of pulmonary and systemic infection. Deletion of gene ID112092, which codes for a hypothetical extracellular protein of unknown function, resulted in significant reduction of virulence.Although pathogenesis is a multifactorial process, these findings highlight the crucial role of surface and secreted proteins in M. circinelloides virulence and should promote further studies of other differential genes.

A TAL effector-like protein of symbioticMycetohabitansincreases stress tolerance and alters the transcriptome of the fungal hostRhizopus microsporus

“…Though beyond the scope of the current study, such approaches are an attractive first step toward understanding the connection between the observed influence of Btl19-13 on fungal SDS tolerance and the relevant biological function of Btl19-13. In other fungi, intolerance to SDS has been associated with changes not only in lipid metabolism (Gsell et al, 2015), but also fungal virulence (Lopez-Fernandez et al, 2018) and amino acid metabolism (Schroeder and Ikui, 2019). Thus, Btl19-13 could confer a variety of biologically relevant benefits to the fungus, the bacterium, or both.…”

A non-canonical RNAi pathway controls virulence and genome stability in Mucorales

“…All the strains compared for the gene expression analysis were auxotroph for leucine. The strain NRRL3631 was used as an avirulent control for the mice infection experiments [23]. M. circinelloides cultures were grown in rich media YPG pH 4.5 at 26ºC for optimal growth and sporulation.…”

“…The murine infection assays for Mucorales virulence were performed using OF-1 male mice weighing 30g (Charles River, Barcelona, Spain) [13,23,33]. The mice were immunosuppressed with the administration of cyclophosphamide (200 mg/kg of body weight) via intraperitoneal, 2 days prior to infection and once every 5 days thereafter.…”

Genes, Pathways, and Mechanisms Involved in the Virulence of Mucorales

“…A recent example is a comparison between the genomes of the M. circinelloides virulent strain CBS277.49 and the strain with reduced virulent NRRL3631. This genomic comparison allowed the identification of 543 absent genes and 230 discontiguous protein-coding sequences in the avirulent strain [80]. Attention was focused on extracellular proteins because of their strong association with pathogenic potential.…”

“…Attention was focused on extracellular proteins because of their strong association with pathogenic potential. One of these proteins with unknown function, encoded by the gene ID112092, resulted in an essential role in virulence because knock-out mutants in CBS277.49 for gene ID112092 exhibited a similar attenuated virulence in a murine model as NRRL3631, making evident the potential of this genomic approach [80]. Other studies analyzed the genomes of 30 mucormycosis-causing fungi, evidencing a correlation between the copy number of cotH genes (Inner spore coat Protein H, involved in the assembly of several proteins in the inner and outer layer of the spore coat, described in Section 8) and clinical prevalence [81].…”