Comparative Analysis of CRISPR Loci Found in Streptomyces Genome Sequences.

The interspaced short palindromic repeats (CRISPR) system is an immune system widely distributed in prokaryotes, resisting the invasion of the foreign mobile genetic elements like phages or plasmids. In this study, we present the comparative analysis of 182 CRISPR loci found in 46 publicly available complete genome sequences of Streptomyces. Overall, nine direct repeats (DRs) groups are identified while all the 2104 spacers are divided into three main groups according to the multiple sequence alignment. Only 11 spacers are identical with parts of 10 plasmid sequences, which indicates a possible origin. The cas gene clusters near the CRISPR arrays are found to mainly belong to the I-E subtype. These CRISPR loci might play an important role in the genome evolution of Streptomyces.