207
infections, tuberculosis and other organ transplants. Iron acquisition occurs and the
microbial virulence determinant causes iron overload in humans and have been
found to be correlated with increased infection (Nevitt and Thiele 2011). The dimorphic fungal pathogen Histoplasma capsulatum causes intracellular growth of yeasts
and may be the causative agent for pulmonary histoplasmosis. Several human and
murine experiments demonstrate that SID1 (coding for L-ornithine-N(5)monooxygenase) expression is required for siderophore biosynthesis by H. capsulatum and hence inhibition of SID1 expression would reduce the virulence of
H. capsulatum yeasts (Hilty et al. 2011). Cryptococcus neoformans controls the
iron levels using the polysaccharide capsule and melanin virulence factors. This
pathogen is known to cause meningoencephalitis in ImC people by acquiring iron
through the reductants from the cell surface and secretion. In addition, permease/
ferroxidase uptake system and transporters of siderophores are also involved in
causing infection (Jung and Kronstad 2008). Rhizopus oryzae causes mucormycosis
in several patients. Patients who undergo deferoxamine treatment are susceptible to
mucormycosis. Deferoxamine also serves as a siderophore that delivers free Fe to
R. oryzae and remains as a major cause of mucormycosis. Other iron chelators, such
as deferiprone, do not deliver free ion and hence are used in iron-chelation therapy
to treat mucormycosis (Ibrahim et al. 2006).
Siderophores are the virulence factors for iron-transport functions because of
their iron acquisition property. Siderophore biosynthesis and its iron uptake suggests possible therapeutic targets to treat fungal infection (Nyilasi et al. 2005). The
most life- threatening fungal pathogens such as aspergillus, candida and Cryptococcus
utilize the siderophore-mediated iron uptake mechanism for various purposes like
propagation or resistance to oxidative stress, survival and virulence that occur
in vivo during infection. Pathogens release siderophores in order to prevent the loss
of iron. Hence, the fungal siderophore biosynthetic pathways along with their biological mechanisms serve as a target for antifungal therapy (Balhara et al. 2016).
12.8 Conclusion
Fungal siderophores are less studied when compared to bacterial siderophores.
They possess both beneficial and harmful effects on humans. Knowledge on fungal
siderophores could be useful to advance the current treatments on fungal infections
and fungal diseases. Interestingly, fungal siderophores are useful in cancer therapy.
Text mining helped us retrieve relevant articles on fungal siderophores.
Bioinformatics approaches helped us identify the genes and protein targets. We also
discussed on the pathogenicity of fungal siderophores. Our summary on fugal
siderophores is based on PubMed articles retrieved by our simple text-mining
approaches. We believe that our finding will be useful to microbiologists to carry
out several future studies on fungal siderophores.
12 A Summary on Up-To-Date Research on Fungal Siderophores on Disease…
infections, tuberculosis and other organ transplants. Iron acquisition occurs and the
microbial virulence determinant causes iron overload in humans and have been
found to be correlated with increased infection (Nevitt and Thiele 2011). The dimorphic fungal pathogen Histoplasma capsulatum causes intracellular growth of yeasts
and may be the causative agent for pulmonary histoplasmosis. Several human and
murine experiments demonstrate that SID1 (coding for L-ornithine-N(5)monooxygenase) expression is required for siderophore biosynthesis by H. capsulatum and hence inhibition of SID1 expression would reduce the virulence of
H. capsulatum yeasts (Hilty et al. 2011). Cryptococcus neoformans controls the
iron levels using the polysaccharide capsule and melanin virulence factors. This
pathogen is known to cause meningoencephalitis in ImC people by acquiring iron
through the reductants from the cell surface and secretion. In addition, permease/
ferroxidase uptake system and transporters of siderophores are also involved in
causing infection (Jung and Kronstad 2008). Rhizopus oryzae causes mucormycosis
in several patients. Patients who undergo deferoxamine treatment are susceptible to
mucormycosis. Deferoxamine also serves as a siderophore that delivers free Fe to
R. oryzae and remains as a major cause of mucormycosis. Other iron chelators, such
as deferiprone, do not deliver free ion and hence are used in iron-chelation therapy
to treat mucormycosis (Ibrahim et al. 2006).
Siderophores are the virulence factors for iron-transport functions because of
their iron acquisition property. Siderophore biosynthesis and its iron uptake suggests possible therapeutic targets to treat fungal infection (Nyilasi et al. 2005). The
most life- threatening fungal pathogens such as aspergillus, candida and Cryptococcus
utilize the siderophore-mediated iron uptake mechanism for various purposes like
propagation or resistance to oxidative stress, survival and virulence that occur
in vivo during infection. Pathogens release siderophores in order to prevent the loss
of iron. Hence, the fungal siderophore biosynthetic pathways along with their biological mechanisms serve as a target for antifungal therapy (Balhara et al. 2016).
12.8 Conclusion
Fungal siderophores are less studied when compared to bacterial siderophores.
They possess both beneficial and harmful effects on humans. Knowledge on fungal
siderophores could be useful to advance the current treatments on fungal infections
and fungal diseases. Interestingly, fungal siderophores are useful in cancer therapy.
Text mining helped us retrieve relevant articles on fungal siderophores.
Bioinformatics approaches helped us identify the genes and protein targets. We also
discussed on the pathogenicity of fungal siderophores. Our summary on fugal
siderophores is based on PubMed articles retrieved by our simple text-mining
approaches. We believe that our finding will be useful to microbiologists to carry
out several future studies on fungal siderophores.
12 A Summary on Up-To-Date Research on Fungal Siderophores on Disease…