Investigation of the Fim1 putative pilus locus of subspecies .

The Gram-positive bacterium subspecies () is the causative agent of strangles, among the most frequently diagnosed infectious diseases of horses worldwide. Genome analysis of strain 4047 (4047) identified a putative operon, Fim1, with similarity to the pilus loci of other Gram-positive bacteria. The Fim1 locus was present in all strains of and its close relative subspecies () that have been studied to date. In this study we provide evidence that the putative structural pilus proteins, SEQ_0936 and CNE, are produced on the cell surface during growth and infection. Although the proteins encoded within the Fim1 locus are not essential for attachment or biofilm formation, over-transcription of SEQ_0936 and CNE enhanced attachment to equine tissue . Our data suggest that whilst the Fim1 locus does not produce a polymerized pilus structure, the products of the Fim1 locus may fulfil an adhesive function. The putative pilus-associated regulator, , which contains a nonsense mutation in , was able to regulate transcription of the Fim1 locus following repair and over-transcription, confirming its predicted role in the operon.