Unraveling the complexities underlying sulfur deficiency and starvation in the cyanobacterium Anabaena sp. PCC 7120

The present study focuses to decipher the impact of long-term sulfur deficiency in the cyanobacterium Anabaena sp. PCC 7120. Cell growth parameters (cell biomass and photopigments) were analysed under varying long-term sulfur deficiency showed significant reduction in growth under sulfur limitations. The reminiscent growth of cyanobacterium in the sulfur shortage possibly pertained to minimize cell size and spherical cell shape. Additionally, lower sulfur availability exhibited negative impacts on photopigments, D1 protein (all3572) transcription and PSII efficiency in the cyanobacterium. Furthermore, depletion in protein and corresponding increase in carbohydrate and lipid contents were interpreted as reprogrammed C-allocation. Additionally, enzyme assay of ATP sulfurylase depicted increased activity in the deficient conditions. Moreover, decreased intracellular concentrations of Mg2+, Fe2+, Ca2+, Na+, and K+ at low sulfur supplementations might be a consequence of counter-ion balancing and attributed to lipid peroxidation and electrolyte leakage resulted from increased ROS. In addition, overexpression of desC followed by fatty acid unsaturation and programmed cell death markers were also noticed. Overall, the result suggest that reduced biomass in sulfur limitation is a cumulative outcome of disrupted photosynthesis, reprogrammed C-allocation, reduced electrolyte contents, and subsequent PCD in the cells of Anabaena sp. PCC 7120 reveal S deficiency exerts an adverse impact on cyanobacterial population and reduces primary productivity.