Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) is an adaptive immune system that resists foreign genes through nuclease targeting in bacteria and archaea. In this study, we analyzed 68 strains of Lactobacillus casei group from the NCBI GenBank database, and bioinformatic tools were used to investigate the occurrence and diversity of CRISPR system. The results showed that a total of 30 CRISPR loci were identified from 27 strains. Apart from three strains which contained double loci with distinguishable distributed sites, most strains contained only one CRISPR locus. The analysis of direct repeat (DR) sequences showed that all DR could form stable RNA secondary structures. The CRISPR spacers showed diversity, and their origin and evolution were revealed through the investigation of their spacer sequences. In addition, a large number of CRISPR spacers showed perfect homologies to phage and plasmid sequences. Collectively, our results would contribute to researches of resistance in L. casei group, and also provide a new vision on the diversity and evolution of CRISPR/Cas system.

中文翻译：

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干酪乳杆菌组中CRISPR基因座的发生和多样性。

簇状规则间隔的短回文重复序列（CRISPR）是一种自适应免疫系统，可通过靶向细菌和古细菌的核酸酶来抵抗外源基因。在这项研究中，我们从NCBI GenBank数据库中分析了68株干酪乳杆菌菌株，并使用生物信息学工具研究了CRISPR系统的发生和多样性。结果显示，从27个菌株中鉴定出总共30个CRISPR基因座。除了三个含有双基因座且具有可区分的分布位点的菌株外，大多数菌株仅包含一个CRISPR基因座。直接重复（DR）序列的分析表明，所有DR均可形成稳定的RNA二级结构。CRISPR间隔区显示出多样性，并且通过研究其间隔区序列揭示了它们的起源和进化。此外，大量CRISPR间隔子与噬菌体和质粒序列表现出完美的同源性。总的来说，我们的结果将有助于干酪乳杆菌组的抗性研究，并为CRISPR / Cas系统的多样性和进化提供新的视野。