An Efficient Protocol for Long-Term Preservation of Cyanobacteria

A simple modification in preparation of nutrient agar meant for agar slants resulted in a convenient and efficient matrix for long term cyanobacterial preservation. In the modified protocol, agar concentration was increased and cyanobacterial cells were mixed rapidly in the molten agar before solidification. Solidified mixture was cut into cubes and air dried. The resulting agar flakes were stored in the dark. Periodically some flakes were inoculated in fresh medium to study regeneration of viable filaments in order to access the efficiency of the method in preserving cyanobacteria in dehydrated form. Possible outer contamination could be removed by washing the agar flakes in 1% sodium hypochlorite for one minute prior to their inoculation in fresh medium. The percentage of agar used and amount of cyanobacterial cells entrapped were the factors that influenced the period of preservation. A comparison of some biochemical and physiological characters in six regenerated cyanobacterial strains to their free-living counterparts showed that the dried agar flakes were completely reliable as preserving material for at least a period of three years. During this period the entrapped cyanobacterial cells did not need further maintenance. This process of maintaining cyanobacteria is extremely convenient as it reduces (1) input of chemicals and man power required for maintaining cyanobacteria in batches (2) possible cross-contamination among various cyanobacteria maintained in liquid batch cultures (3) use of glassware and (4) storage space. In addition, the cells could be maintained in a near dormant state, and that minimized the chances of alterations in their native characters.