Laboratory of Bacteriology, The Rockefeller University, New York, NY 10065, USA.
Cell Host Microbe. 2012 Aug 16;12(2):177-86. doi: 10.1016/j.chom.2012.06.003.
Pathogenic bacterial strains emerge largely due to transfer of virulence and antimicrobial resistance genes between bacteria, a process known as horizontal gene transfer (HGT). Clustered, regularly interspaced, short palindromic repeat (CRISPR) loci of bacteria and archaea encode a sequence-specific defense mechanism against bacteriophages and constitute a programmable barrier to HGT. However, the impact of CRISPRs on the emergence of virulence is unknown. We programmed the human pathogen Streptococcus pneumoniae with CRISPR sequences that target capsule genes, an essential pneumococcal virulence factor, and show that CRISPR interference can prevent transformation of nonencapsulated, avirulent pneumococci into capsulated, virulent strains during infection in mice. Further, at low frequencies bacteria can lose CRISPR function, acquire capsule genes, and mount a successful infection. These results demonstrate that CRISPR interference can prevent the emergence of virulence in vivo and that strong selective pressure for virulence or antibiotic resistance can lead to CRISPR loss in bacterial pathogens.
病原菌的出现主要是由于毒力和抗生素耐药基因在细菌之间的转移，这个过程被称为水平基因转移（HGT）。细菌和古菌的成簇规律间隔短回文重复序列（CRISPR）位点编码了针对噬菌体的序列特异性防御机制，并构成了 HGT 的可编程障碍。然而，CRISPR 对毒力出现的影响尚不清楚。我们用人病原体肺炎链球菌的 CRISPR 序列靶向荚膜基因，荚膜基因是肺炎链球菌的一个重要毒力因子，结果表明 CRISPR 干扰可以防止非荚膜、无毒性肺炎链球菌在感染小鼠时转化为荚膜、毒性菌株。此外，细菌以低频率丧失 CRISPR 功能，获得荚膜基因，并成功感染。这些结果表明，CRISPR 干扰可以防止体内毒力的出现，而毒力或抗生素耐药性的强烈选择性压力可能导致细菌病原体中 CRISPR 的丧失。
