CHARACTERIZATION OF DNA RESTRICTION-MODIFICATION SYSTEMS IN SPIRULINA-PLATENSIS STRAIN PACIFICA

Four unique restriction enzymes were identified in the soluble protein fraction of Spirulina platensis strain pacifica, a commercially impor tant strain of marine cyanobacterium that is used as a supplement in a human diets. These are SpaI, SpaII, SpaIII and SpaIV, which are isosc hizomers of Tth1 11I, PvuI, PvuII and HindIII, respectively. The recog nition sites of each of these four enzymes were identified by restrict ion digests of different plasmid DNAs of known sequence and determinin g the cleavage sites by sequencing. SpaI is the most predominant restr iction enzyme present in S. platensis strain pacifica. It shows high a ctivity at 37 degrees C compared to 65 degrees C for its isoschizomer Tth111I.