Restriction modification systems
RM (Restriction Endonucleases) systems are widely distributed among cyanobacteria to protect themselves from invasion by foreign DNA such as bacteriophage genomes and plasmids. In general, the system composed of a pairs of opposing enzyme activities, restriction endonuclease and DNA methyltransferase. Restriction endonucleases will digest DNA material at specific sites while the cognate DNA methyltranferases will modify the resident DNA by specific methylation and protect it from restriction. The availability of genomic sequence data are extremely useful in searching for novel RM genes using bioinformatics tools.
Currently, based on available genomic information of four Arthrospira spp., four types of RM systems have been identified from these species. The information of RM systems gained from the analysis of Arthrospira genomes including the A. platensis C1 will help in understanding the defense mechanism of these strains in various environment conditions.