Table 1. Summary of the strains, plasmids and primers used.

Strain, plasmid or primer	Description/purpose	Reference or source
E. coli strains
C50041	Wild-type strain	Qiuchun et al. (2009)
χ7213	For cloning pGMB151	Kang et al. (2002)
S17-λpir (SmR)	For cloning pGMB151	Huang et al. (2004)
ΔspiA	spiA mutant	This study
ΔspiAR	Complementation of ΔspiA	This study
Plasmids
pUC18(Ampr)	Plasmid for cloning	Promega
pMD18-T	Plasmid for cloning	Takara
pGMB151(Ampr Smr)	Suicide plasmid	Huang et al. (2004)
pBluescript II SK(−)	Plasmid for cloning	Fermentas
pUC4K	Plasmid for kanamycin-resistance gene	Amersham
pGEX-6P-1	Plasmid for spiA gene restoration and csgA gene expression	Amersham
Primers
12	5′-CTCGGATCCCACTATGTACTTGAGTCGTATCATTGCG-3′ (spiA sense, BamHI site underlined)	This study
13	5′-CTCGTCGACCCCTTTATGCCAGACAAATGCCA-3′ (spiA antisense, SalI site underlined)	This study
14	5′-CTCGAATTCGCGTAAGTAATGAATGAACCGTCC-3′ [pBluescript II SK(−)+spiA1 sense, EcoRI site underlined]	This study
15	5′-CTCGAATTCCGGGTTCTTTGTTGCGCGTT-3′ [pBluescript II SK(−)+spiA2 antisense, EcoRI site underlined]	This study
16	5′-CAGTGACAGGTTACCTTCATTCAGC-3′ (spiA sense, spiA design primer)	This study
17	5′-CTCGGATCCCCCTTTATGCCAGACAAATGCCA-3′ (spiA antisense, BamHI site underlined)	This study
18	5′-GAATTCTCAAAGCCACGTTGTGTCTCAAA-3′ (kanamycin sense, EcoRI site underlined)	This study
19	5′-GAATTCCGCTGAGGTCTGCCTCGT-3′ (kanamycin antisense, EcoRI site underlined)	This study
20	5′-TGCAAGTTAAAGCCAGGTG-3′ (spiC sense)	This study
21	5′-CCGAAGGTAATAGCCGATCC-3′ (spiC antisense)	This study
22	5′-GAGGTATCGCTGATTACCGTTG-3′ (spiA sense)	This study
23	5′-CGTGAGTGTATTGCGTAGGATG-3′ (spiA antisense)	This study
24	5′-CACTGGCGCAGGCAGATAC-3′ (ssaD sense)	This study
25	5′-GATCAGCAATGGCGTAAGGTTC-3′ (ssaD antisense)	This study
26	5′-CTCGGATCCATGGTAGTAAATAAACGTTTAATC-3′ (spiA complementation sense, BamHI site underlined)	This study
27	5′-CTCCTCGAGTTAACCATGAGATATGCCATTATTTAC-3′ (spiA complementation antisense, XhoI site underlined)	This study