Siderophores Case Study

2.1.5. Role of Siderophore in metal remediation:

Siderophores are low-molecular mass (400–1,000 Daltons) compounds with high association constants for complexing iron, but they can also form stable complexes with other metals, such as Al, Cd, Cu, Ga, In, Pb and Zn (Glick and Bashan, 1997; Schalk et al., 2011). Although siderophores contain other functional groups, they are broadly classified into three main groups based on the chemical nature of the moieties donating the oxygen ligands for Fe(III) coordination, which are either of the catecholates (enterobactin), hydroxamates (desferrioxamines), or (α-hydroxy-)carboxylates (aerobactin).

Microbes synthesize chelating agents in the form of siderphores that bind heavy metals and cause an increase in bioavailability through complexation reactions (Gadd, 2010; Rajkumar et al., 2010). Production of siderphores is reported in diverse group of bacteria. However, PGP bacteria are better known for siderphore production in diverse environmental conditions including elevated

For instance, Joshi and Juwarkar (2009) investigated the immobilization of Cd and Cr after inoculation of EPS producing Azotobacter spp. and found that these isolates were able to bind 15.2 mg g-1 of Cd and 21.9 mg g-1 of Cr. Similarly Gonzalez-Chavez et al. (2004) assessed the ability of arbuscular mycorrhizal fungi (AMF) produced insoluble glycoprotein, glomalin to form complexes with heavy metals and found that up to 4.3 mg Cu, 1.1 mg Pb and 0.1 mg Cd per gram of glomalin could be extracted from metal polluted soils. Since there is a correlation between the amount of glomalin in the soil and the amount of heavy metal bound, AMF strains with significant secretion of glomalin should be more suitable for phytostabilization