Influence of environmental stress on virulence gene expression in Vibrio anguillarum

The aim of the research presented in this thesis was the study of the environmental stress influence on the expression of virulence genes in the fish pathogen Vibrio anguillarum. Analyses were carried out by means of Real Time PCR methodology. The study includes three different chapters; the first one is related to a general screening of virulence gene expression induced by changes in temperatures salinity and iron depletion. Results showed that the most evident response was related to angR and fatA (plasmidic genes) under iron starvation condition. The chapter 2 concerns the empA protease expression, production and induction by the same stress analyzed in the first chapter, Results showed the influence of salinity on the production of metallo-protease in vibrio anguillarum. Finally the third chapter is related to new methodology to quantify vibrio anguillarum cells directly in infected fish tissues. Results showed that a direct quantification can be obtained using toxR as a target gene, while 16SrDNA could be a good target to increase the sensitivity of detection.