149
redox cycling processes to form reduced Fe which on further reaction with hydrogen peroxide generates more number of oxygen radicals for cellulose, hemicellulose, and lignocellulose depolymerization (Xu and Goodell 2001; Arantes and
Milagres 2007). It was reported that bio-bleaching of pulps by fungus is facilitated
by acting on the viscosity (Milagres et al. 2002), where different percentage of viscosity loss were observed for G. trabeum (10.8%), Perenniporia medulla-panis
(13.6%), and Tinea versicolor (14.4%), and also by altering the lignin structure
(Wang et al. 2008).
The saprophytic fungi A. fumigatus and A. nidulans produce 55 similar types of
siderophores which are reported mainly in the recycling purpose of environmental
carbon and nitrogen. The iron capturing by siderophore in the soil environment
notably reduces the toxicity emitted by asbestos fiber and chrysotile, which naturally has the ability to release high concentration of iron (Mohanty et al. 2017). And
the activity was relatively highly observed by the fungal siderophores than bacteria.
9.4.3 Health Care
In the present era, fungal infections among immunocompromised patients and resistant clinical strains are highly threatening mankind and even provoke the nonpathogenic to a virulent strain. Perhaps the iron uptake and transport mechanism of fungi
are found to be unique; the fungal siderophore biosynthetic pathway might serve as
a selective therapeutic intervention. The genomics study revealed the specific genes
responsible for siderophore biosynthesis which on further extension with proteomics analysis would render the elucidation of structural and functional knowledge on enzymes. This might facilitate the design and development of selective
fungicidal agents.
In fungi, as mentioned earlier, the importance of siderophores is revealed for
germ tube formation, sporulation, and stress resistance, and even the mutant studies
indicated the attenuation of fungal virulence (Scharf et al. 2014). The mutant studies
on the genes responsible for extracellular and intracellular siderophore under the
iron-limitation as well as iron-sufficient condition clearly depicted its functionality
in the fungi A. fumigatus. Mutating the genes sidI, sidH, sidF, and sidD in A. fumigatus which are responsible for extracellular siderophores, there was decreased
growth, conidiation, and oxidative stress resistance. And eliminating the genes
involved in the intracellular siderophore production (sidC and sidL) blocked the
sexual development as well as reduced conidia formation. Another approach of
inactivating the entire siderophore system resulted in the high sensitivity due to iron
starvation and is directly related to the virulent factors of the pathogen (Haas 2014).
C. albicans being a commensal in the gut region of mammals exhibits SFU1 expression to shut down the Fe uptake to overcome intracellular toxicity due to Fe abundance (Chen et al. 2011). Several other importance of siderophores for fungi specify
their predominant essentiality in infecting animal or plant hosts. Siderophore biosynthesis being unique in fungi, drug development would be highly appreciated to
9 Fungal Siderophores: Prospects and Applications
redox cycling processes to form reduced Fe which on further reaction with hydrogen peroxide generates more number of oxygen radicals for cellulose, hemicellulose, and lignocellulose depolymerization (Xu and Goodell 2001; Arantes and
Milagres 2007). It was reported that bio-bleaching of pulps by fungus is facilitated
by acting on the viscosity (Milagres et al. 2002), where different percentage of viscosity loss were observed for G. trabeum (10.8%), Perenniporia medulla-panis
(13.6%), and Tinea versicolor (14.4%), and also by altering the lignin structure
(Wang et al. 2008).
The saprophytic fungi A. fumigatus and A. nidulans produce 55 similar types of
siderophores which are reported mainly in the recycling purpose of environmental
carbon and nitrogen. The iron capturing by siderophore in the soil environment
notably reduces the toxicity emitted by asbestos fiber and chrysotile, which naturally has the ability to release high concentration of iron (Mohanty et al. 2017). And
the activity was relatively highly observed by the fungal siderophores than bacteria.
9.4.3 Health Care
In the present era, fungal infections among immunocompromised patients and resistant clinical strains are highly threatening mankind and even provoke the nonpathogenic to a virulent strain. Perhaps the iron uptake and transport mechanism of fungi
are found to be unique; the fungal siderophore biosynthetic pathway might serve as
a selective therapeutic intervention. The genomics study revealed the specific genes
responsible for siderophore biosynthesis which on further extension with proteomics analysis would render the elucidation of structural and functional knowledge on enzymes. This might facilitate the design and development of selective
fungicidal agents.
In fungi, as mentioned earlier, the importance of siderophores is revealed for
germ tube formation, sporulation, and stress resistance, and even the mutant studies
indicated the attenuation of fungal virulence (Scharf et al. 2014). The mutant studies
on the genes responsible for extracellular and intracellular siderophore under the
iron-limitation as well as iron-sufficient condition clearly depicted its functionality
in the fungi A. fumigatus. Mutating the genes sidI, sidH, sidF, and sidD in A. fumigatus which are responsible for extracellular siderophores, there was decreased
growth, conidiation, and oxidative stress resistance. And eliminating the genes
involved in the intracellular siderophore production (sidC and sidL) blocked the
sexual development as well as reduced conidia formation. Another approach of
inactivating the entire siderophore system resulted in the high sensitivity due to iron
starvation and is directly related to the virulent factors of the pathogen (Haas 2014).
C. albicans being a commensal in the gut region of mammals exhibits SFU1 expression to shut down the Fe uptake to overcome intracellular toxicity due to Fe abundance (Chen et al. 2011). Several other importance of siderophores for fungi specify
their predominant essentiality in infecting animal or plant hosts. Siderophore biosynthesis being unique in fungi, drug development would be highly appreciated to
9 Fungal Siderophores: Prospects and Applications