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 important strain of marine cyanobacterium that is used as a supplement in a human diets. These are SpaI, SpaII, SpaIII and SpaIV, which are isoschizomers of Tth111I, Pvul, PvuII and HindIII, respectively. The recognition sites of each of these four enzymes were identified by restriction digests of different plasmid DNAs of known sequence and determining the cleavage sites by sequencing. SpaI is the most predominant restriction enzyme present in S. platensis strain pacifica. It shows high activity at 37 °C compared to 65 °C for its isoschizomer Tth111I.Department of Plant Molecular Physiology