Homology analysis of CRISPR-Cas system in Lactic acid bacteria

To analyze the homology CRISPR-Cas systems in Lactic acid bacteria. Bioinformatics method was used for predicting CRSPR-Cas system of Lactic acid bacteria that published in NCBI.There phylogenetic analysis was performed to investigate the level of conservation and divergence between the identified Lactic acid bacteria CRISPR immune systems using the repeats and universal Cas protein. Streptococcus thermophilus,Lactobacillus delbrueckii subsp.bulgaricus and Lactobacillus helveticus all contain different number of CRISPR-Cas systems,the repeats of each type were highly conserved and the Cas proteins demonstrated high similarity. For homology analysis,repeats and Cas proteins showed high similarity with several individual species of distant relationships,which suggested that the CRISPRs of tested strains also had the characteristic of horizontal gene transfer( HGT).