38
while A. nidulans very rarely causes IA. Due to delay in phagocytosis, there is difference in immune response of A. fumigatus against A. nidulans and also the recognition characteristics of A. Nidulans involves in slower cell migration and
phagocytosis and also increases cytokine production. The biosynthetic pathways of
A. fumigatus and A. nidulans are essential to understand the association of siderophoric systems involved in aspergillosis disease and their associated genes.
3.3.1 Aspergillus fumigatus
Aspergillus fumigatus produces more asexual spores that are widespread in the environment. These spores spread in the environmental air constantly inhaled by human
and are usually removed by a functional immune system (Brakhage and Langfelder
2002; Latge 2001). However, patients with weakened immune system due to organ
or bone marrow transplantation and cancer chemotherapy or those with renal failure
have a higher risk of these fungal infections, termed as aspergillosis. A. fumigatus is
commonly referred to as the most common airborne fungal pathogen in human.
3.3.2 Aspergillus nidulans
A. nidulans is an important aerobe which survives in anaerobic environment.
Occasionally, A. nidulans causes human disease and belongs to filamentous model
fungus. A. nidulans is a well-studied fungus which is closely related to several
Aspergillus species, such as A. fumigatus (Brookman and Denning 2000). Aspergillus
nidulans produces two main siderophores such as triacetylfusarinine C (TAFC) and
ferricrocin (FC) (Charlang et al. 1981; Oberegger et al. 2001). The filamentous fungus A. nidulans synthesizes three major siderophores, namely, fusigen, triacetylfusarinine C, and ferricrocin. Putative genes of A. nidulans such as
metalloreductase- encoding gene are also extracted (Oberegger et al. 2002).
3.3.3 Siderophore Biosynthetic Pathway in A. fumigatus
and A. nidulans
Siderophores are known to play an essential part in the iron metabolism and fungal
virulence. A. fumigatus and A. nidulans expel the siderophore triacetylfusarinine C
(TAFC) which is involved in iron acquisition. An extensive literature survey was
performed to identify the genes associated with siderophoric pathway, and input
data were taken from publicly available databases for the analysis. Table 3.2 gives
the Aspergillus spp. with their associated genes and siderophoric activity. About 20
genes are known to be responsible for iron homeostasis maintenance in A.
S. Jayapalan et al.
while A. nidulans very rarely causes IA. Due to delay in phagocytosis, there is difference in immune response of A. fumigatus against A. nidulans and also the recognition characteristics of A. Nidulans involves in slower cell migration and
phagocytosis and also increases cytokine production. The biosynthetic pathways of
A. fumigatus and A. nidulans are essential to understand the association of siderophoric systems involved in aspergillosis disease and their associated genes.
3.3.1 Aspergillus fumigatus
Aspergillus fumigatus produces more asexual spores that are widespread in the environment. These spores spread in the environmental air constantly inhaled by human
and are usually removed by a functional immune system (Brakhage and Langfelder
2002; Latge 2001). However, patients with weakened immune system due to organ
or bone marrow transplantation and cancer chemotherapy or those with renal failure
have a higher risk of these fungal infections, termed as aspergillosis. A. fumigatus is
commonly referred to as the most common airborne fungal pathogen in human.
3.3.2 Aspergillus nidulans
A. nidulans is an important aerobe which survives in anaerobic environment.
Occasionally, A. nidulans causes human disease and belongs to filamentous model
fungus. A. nidulans is a well-studied fungus which is closely related to several
Aspergillus species, such as A. fumigatus (Brookman and Denning 2000). Aspergillus
nidulans produces two main siderophores such as triacetylfusarinine C (TAFC) and
ferricrocin (FC) (Charlang et al. 1981; Oberegger et al. 2001). The filamentous fungus A. nidulans synthesizes three major siderophores, namely, fusigen, triacetylfusarinine C, and ferricrocin. Putative genes of A. nidulans such as
metalloreductase- encoding gene are also extracted (Oberegger et al. 2002).
3.3.3 Siderophore Biosynthetic Pathway in A. fumigatus
and A. nidulans
Siderophores are known to play an essential part in the iron metabolism and fungal
virulence. A. fumigatus and A. nidulans expel the siderophore triacetylfusarinine C
(TAFC) which is involved in iron acquisition. An extensive literature survey was
performed to identify the genes associated with siderophoric pathway, and input
data were taken from publicly available databases for the analysis. Table 3.2 gives
the Aspergillus spp. with their associated genes and siderophoric activity. About 20
genes are known to be responsible for iron homeostasis maintenance in A.
S. Jayapalan et al.