Physico-chemical parameters influencing DNase activity of the cyanobacterium Spirulina platensis

The effects of temperature, Mg2+, EDTA concentration and rinsing on extra- and intra-cellular DNase activity of Spirulina platensis strain SSP-14, wer e investigated. The results indicate that the tested strain contains very h igh extra- and intracellular DNase activity, which actually hinders the tra nsfer of foreign gene(s) to S. platensis, a cyanobacterium with multiple ec onomic potentials. The extracellular DNase activity could easily be removed by rinsing the cells with Zarrouk medium more than once. The intracellular DNase activity could also be inhibited by (1) removal of Mg2+, (2) maintai ning EDTA concentration above 1 mmol l(-1), and (3) manipulating below 0-4 degrees C, during all the incubation procedures. We suggest that, by using one or more of, or combining, all those experimental conditions, the chance s of foreign DNA attempted to be introduced into S. platensis without being digested would be increased.