Identification of the transcriptional start site of the mfa1 gene 
To identify the promoter region of mfa1, the transcriptional start site was first determined.
The RACE experiment was first conducted with mfa1-specific reverse primers MfaTSR1 located at 135 bp up-stream of the potential start codon and MfaTSR2 located at 37 bp downstream of the potential start codon (Fig. 2a).
The transcriptional start site (the A) of mfa1 was at 434 bp upstream from the potential start codon (Fig. 2b).
To verify the result, the RACE experiment was repeated with mfa1-specific reverse primers MfaTSR3 and MfaTSR4 located at 237 bp upstream of the potential start codon.
The same transcriptional start site was identified.
To confirm the result of RACE, reverse-transcriptional PCR using three sets of primers was performed.
As shown in Fig. 2c, the PCR product was generated only with primers MfaTSF1 (corresponding to +6 to +25) and MfaTSR5 (+805 to +824).
There was no PCR product generated from RT-PCR using the primers (MfaTSF3, from -139 to -121 or MfaTSF2, from -66 to -47) which correspond to the DNA sequences upstream from the transcriptional start site.
This transcriptional start site is 390 bp upstream of the site previously reported (Park et al., 2006).
It is likely that mfa1 gene possesses two functional promoters, which are also detected in the fimA gene of P. gingivalis (Xie & Lamont, 1999; Nishikawa et al., 2004).
