Table 1.

Bacterial strains and transposons used in this study

Bacterial strain or transposon	Comments	Reference or source
Clostridium difficile 630	Sequenced strain of ribotype 012	35
Clostridium difficile 630Δerm	Erythromycin-sensitive derivative of the genome strain	14
Clostridium difficile R20291	Ribotype 027, responsible for the Stoke Mandeville outbreak in the United Kingdom	31
Clostridium difficile FM168	Recipient strain CD37 containing Tn5397 and Tn916ΔE	34
Bacillus subtilis CU2189	Recipient strain	9
Bacillus subtilis BS34A	B. subtilis CU2189::Tn916, containing a single copy of Tn916	26
Bacillus subtilis BS59A	B. subtilis CU2189 containing a single copy of Tn916ΔE from FM168	This study
Tn916	Tetracycline resistance-encoding conjugative transposon	11
Tn916ΔE	Erythromycin resistance-encoding derivative of Tn916	27