Allelic Replacement of speH 
Increased expression of speH during pharyngeal cell adherence suggests that the SpeH exotoxin is either necessary for adherence, or is a component of a downstream infection process.
Adherence-mediated upregulation of speH is likely not the result of phage induction, as the remaining phage 370.2 genes identified in our analysis were downregulated.
To determine if SpeH plays a direct role in the adherence process, we created a deletion mutant in strain SF370 (SF370DeltaspeH), which was confirmed by PCR (unpublished data) and RT-PCR (Figure 1A) and tested in vitro for adherence to human pharyngeal cells.
We observed no significant difference in adherence between the wild-type (SF370) and mutant strains (Figure 1B), indicating that SpeH is not involved directly in attachment to the pharyngeal cell.
The significant upregulation of the speH gene during adherence suggests that the gene product may function instead during a subsequent stage of infection.
