PPIB and infection: Two additional Ps sequences encoding for putatively secreted proteins identified apart from the current study (H.L.Williams, unpublished data) were added to the list of potential virulence factors: a 1,4 benzoquinone reductase, originally identified as a protein up-regulated during infection of DF [9] (partial gene sequence in Additional file 5), and a cyclophilin, which was identified as a prevalent protein in Ps mycelia grown on malt extract [GenBank: JX848541].