Proteomic analyses of the cyanobacterium Arthrospira (Spirulina) platensis under iron and salinity stress

Arthrospira platensis is a species of filamentous cyanobacteria whose high protein content renders it suitable as a nutritive supplement for human and animal diets. Furthermore it is easy to grow as it tolerates a broad range of environmental stresses such as extremes of pH, salinity and heavy metals. In this study, changes in the growth, pigments and proteome of A. platensis were analyzed under two major abiotic stresses limiting productivity, salinity and iron. The lower concentrations of stresses showed varied effects on fresh weight, growth rate, pigment constituents and soluble protein of A. platensis. A proteomic analysis was conducted using SDS-PAGE first to obtain an overview of gross changes, followed by 2-DE and mass spectrometry to identify specific proteins whose abundance was affected by these environmental stresses. Eighteen spots were differentially expressed under the stress conditions. Of these, six were found with increased abundance responding only to Fe2+ stress, and five as a result of NaCl stress alone. Using LC–MS/MS, 37 proteins were identified within these spots. These proteins were classified into thirteen categories according to their function annotation. The present analysis could provide important data related to stress-tolerance by microalgae.