Toxin-antitoxin (TA) systems are widespread on mobile genetic elements and in bacterial chromosomes. In type I TA, synthesis of the toxin protein is prevented by the transcription of an antitoxin RNA. The first type I TA were recently identified in the human enteropathogen Clostridioides difficile. Here we report the characterization of five additional type I TA within phiCD630-1 (CD0977.1-RCd11, CD0904.1-RCd13 and CD0956.3-RCd14) and phiCD630-2 (CD2889-RCd12 and CD2907.2-RCd15) prophages of C. difficile strain 630. Toxin genes encode 34 to 47 amino acid peptides and their ectopic expression in C. difficile induces growth arrest that is neutralized by antitoxin RNA co-expression. We show that type I TA located within the phiCD630-1 prophage contribute to its stability and heritability. We have made use of a type I TA toxin gene to generate an efficient mutagenesis tool for this bacterium that allowed investigation of the role of these widespread TA in prophage maintenance.

毒素-抗毒素（TA）系统广泛存在于移动遗传元件和细菌染色体中。在I型TA中，抗毒素RNA的转录阻止了毒素蛋白的合成。第一类I TA是最近在人体肠病原艰难梭菌中鉴定的。在这里我们报告了phiCD630-1（CD0977.1- RCd11 ，CD0904.1- RCd13和CD0956.3- RCd14）和phiCD630-2（CD2889 -RCd12和CD2907.2 -RCd15）预言中另外五个I型TA的特性的艰难梭菌菌株630的毒素基因编码34至47个氨基酸的肽，并在其异位表达艰难梭菌诱导被抗毒素RNA共表达中和的生长停滞。我们表明位于phiCD630-1噬菌体中的I型TA有助于其稳定性和遗传性。我们已经利用I型TA毒素基因为该细菌生成了有效的诱变工具，从而可以研究这些广泛的TA在原噬菌维持中的作用。