Unravelling the secrets of siderophore production in cyanobacteria from Meghalaya

The present study examines the role of specific abiotic factors, including nitrogen source, pH, and iron concentration in regulation of siderophore production in five local cyanobacterial isolates (Anabaena sp., Synechococcus sp., Phormidium sp., Neowestiellopsis sp., and Cyanobium sp.) from Meghalaya, Northeast India. To quantify siderophore production, Chrome Azurol S (CAS) liquid assay was used. Maximum siderophore production in tested cyanobacteria occurred during the late exponential phase under iron-limiting conditions, with Synechococcus sp. peaking at 53.62% and Anabaena sp. at 47.32%. Production peaked at 30 µM iron and decreased with higher concentrations. Optimal synthesis occurred at pH 7.0, with reduced activity in more acidic or alkaline conditions. Nitrogen sources also influenced production, with nitrate supplementation yielding the highest levels. Synechococcus sp. and Anabaena sp. produced both hydroxamate and catecholate siderophores, while Phormidium sp., Neowestiellopsis sp., and Cyanobium sp. predominantly produced hydroxamate siderophores. The study demonstrates that several abiotic factors, including pH, iron availability, and nitrogen source, had significant impact on siderophore production. Of the five isolates, Anabaena sp. and Synechococcus sp. are promising candidates for use as biofertilizers due to their high hydroxamate and catecholate siderophore synthesis under all tested abiotic factors.