Long term storage of Cyanobacteria

I wanted to make stocks of cyanobacteria for my work and I found the following method most comfortable.

• Make a solution of 10% v/v methanol using the bacterial medium as solvent NOT just water and autoclave.
• While maintaining sterile conditions, take 0.5 ml of log-phase cyanobacterial culture in a 1.5ml vial.
• To this add 0.5ml of 10% methanol solution.
• Mix by inversion.
• Store the vial at -20 degree Celsius.