Novel strains of Bacillus cereus Wah1 and Enterobacter cloacae Wkh with high potential for production of siderophores

Siderophores are relatively low-weight molecules (500 to 1000 Dalton), which are produced by many microorganisms as the chelating ligands of iron under iron deficiency. Plants can absorb the siderophore-iron complex to meet their needs for iron. The aim of this study was isolation and identification of siderophore producing bacteria.
In this study, we used liquid chrome azurol S (CAS) assay for the isolation of siderophore producing plant growth promoting rhizobacteria (PGPRs). Then, different kinds of the produced siderophores by the best strains were determined using overlaid chrome azurol S (O-CAS) assay. Finally, two best siderophores producing strains were identified using the 16S rDNA gene sequencing analysis.
The results showed that 69.3 percent of the isolated bacteria could produce siderophores. The lowest and highst levels of siderophores belonged to the strains Cke1 (17.58 percent siderophore unit) and Wah1 (97.76 percent siderophore unit) respectively. Based on the O-CAS assay method, these strains produced catchol and hydroxamat types of siderophores. Two strains Wah1 and Wkh were identified using 16S rDNA gene sequencing analysis as Bacillus cereus and Enterobacter cloacae, respectively.
Discussion and Wah1 and Wkh produced more siderophores (as siderophore unit) than other strains, which were studied using the same method until now. Therefore, they could be valuable strains to study their potential as biological fertilizers and plant protection against the soil born pathogens.