3
Holmstrom 2014; Zheng and Nolan 2012; Haas 2003; Luca and Wood 2000;
Riquelme 1996). Thus, it is obvious that much less is known about fungal siderophores when compared to bacterial siderophores. We believe that a brief description
on fungal siderophores might be useful to microbiologists working on their biosynthesis, pathogenesis, biomedical application, and other biological aspects.
1.2 Microorganisms and Iron
Microorganisms depend on a variety of metals for their optimal growth and existence. They influence the nature of the metals by modifying their physical properties
and chemical states. Biomineralization is an emerging discipline that deals with the
process of biogenic mineral formation by microorganisms. It often overlaps with
geomicrobiology. Most of the members of Mendeleev’s Periodic Table are influenced by microorganisms in the formation of biomass or simple accumulation processes. The microorganisms have their intrinsic vehicle system for carrying the vital
metals and minerals through a process called bioprecipitation that consists of three
major mechanisms: (i) by generating primary or secondary metabolites, (ii) by
changing the microecosystem surrounding the metals, and (iii) by discharging the
substances that can precipitate the metals.
The structural components of microorganisms are capable of absorbing metals
by interacting with earthen components. The microorganisms as a whole can transform various metals and minerals. The metal-microbe (or metal-microorganism)
interactions often result in the oxidation or reduction of various components facilitated by the microorganisms. There are multiple variables such as endogenous
chemicals and structural components on which the microbes rely on for their existence. These properties are the primary determinants of the quantity of metals present in the cell. The metal-specific structural components and physiological functions
are known in most of the microorganisms. The structural components are essential
for the absorption of essential metals such as sodium, potassium, calcium, iron, and
many more. The microorganisms have developed a defined and controlled mechanism over the years to acquire metals in the advent of scarcity of the metals. They
compete with other living organisms including the host they infect. The general
mechanisms through which the metal acquisition takes place comprise of two components: (i) membrane transport system for specific metals and (ii) metal- complexing
agents that procure the metals from environment.
The optimal absorption and presence of the essential metals are important
because any excess bioavailability of the metals affect the normal growth and development of the microorganisms. Any superfluous amount of metal can lead to both
morphological alterations and physiological actions of the microorganisms. The
evolutionary capacity of the microorganisms is capable of developing intrinsic
mechanisms such as genetically inherited resistance and redox reactions. These
intrinsic mechanisms result in lesser toxicity and controlled entry at the cell surface
to protect themselves from the metallic overload (Khan et al. 2018). The absorption
1 Basics of Fungal Siderophores: Classification, Iron Transport and Storage…
Holmstrom 2014; Zheng and Nolan 2012; Haas 2003; Luca and Wood 2000;
Riquelme 1996). Thus, it is obvious that much less is known about fungal siderophores when compared to bacterial siderophores. We believe that a brief description
on fungal siderophores might be useful to microbiologists working on their biosynthesis, pathogenesis, biomedical application, and other biological aspects.
1.2 Microorganisms and Iron
Microorganisms depend on a variety of metals for their optimal growth and existence. They influence the nature of the metals by modifying their physical properties
and chemical states. Biomineralization is an emerging discipline that deals with the
process of biogenic mineral formation by microorganisms. It often overlaps with
geomicrobiology. Most of the members of Mendeleev’s Periodic Table are influenced by microorganisms in the formation of biomass or simple accumulation processes. The microorganisms have their intrinsic vehicle system for carrying the vital
metals and minerals through a process called bioprecipitation that consists of three
major mechanisms: (i) by generating primary or secondary metabolites, (ii) by
changing the microecosystem surrounding the metals, and (iii) by discharging the
substances that can precipitate the metals.
The structural components of microorganisms are capable of absorbing metals
by interacting with earthen components. The microorganisms as a whole can transform various metals and minerals. The metal-microbe (or metal-microorganism)
interactions often result in the oxidation or reduction of various components facilitated by the microorganisms. There are multiple variables such as endogenous
chemicals and structural components on which the microbes rely on for their existence. These properties are the primary determinants of the quantity of metals present in the cell. The metal-specific structural components and physiological functions
are known in most of the microorganisms. The structural components are essential
for the absorption of essential metals such as sodium, potassium, calcium, iron, and
many more. The microorganisms have developed a defined and controlled mechanism over the years to acquire metals in the advent of scarcity of the metals. They
compete with other living organisms including the host they infect. The general
mechanisms through which the metal acquisition takes place comprise of two components: (i) membrane transport system for specific metals and (ii) metal- complexing
agents that procure the metals from environment.
The optimal absorption and presence of the essential metals are important
because any excess bioavailability of the metals affect the normal growth and development of the microorganisms. Any superfluous amount of metal can lead to both
morphological alterations and physiological actions of the microorganisms. The
evolutionary capacity of the microorganisms is capable of developing intrinsic
mechanisms such as genetically inherited resistance and redox reactions. These
intrinsic mechanisms result in lesser toxicity and controlled entry at the cell surface
to protect themselves from the metallic overload (Khan et al. 2018). The absorption
1 Basics of Fungal Siderophores: Classification, Iron Transport and Storage…