Exogenous osmolytes suppresses the toxic effects of malathion on Anabaena variabilis

• Malathion induced oxidative stress in Anabaena variabilis.
• Enhancement of endogenous osmolytes suggests their role in tolerance mechanism.
• Exogenous osmolytes addition enhanced growth and antioxidant enzymes activities.
• The present study shows the metabolic protective role of osmolytes.

Role of osmolytes is though well established for salt, drought and chilling stress, but their role in pesticide stress is yet to be explored thoroughly. The sporadic information covers our previous studies on proline with respect to endosulfan and carbaryl pesticides in cyanobacteria. Therefore, during the present investigation importance of osmolytes (exogenous and endogenous) is studied in cyanobacterial biofertilizer Anabaena variabilis in the presence of 25, 50, 75 and 100 μg mL−1 malathion pesticide. Present investigation has two parts. In the first part we showed that malathion exert its toxic effect on growth (biomass) via. malondialdehyde (MDA) and hydrogen peroxide (H2O2). This was associated with quantitative enhancement of endogenous osmolytes (proline, sucrose, mannitol, trehalose and glycogen). In the second part effort was made to corelate effect of exogenous addition of osmolytes (which were detected in the first part of this study) on growth and antioxidant enzymes [like superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX)] of A. variabilis in the presence of 100 μg mL−1 malathion. Surprisingly it was observed that exogenous osmolytes gave additional protection to the organism. The order of protection provided by osmolytes was as trehalose>glycogen>sucrose>mannitol>proline in A. variabilis.