Identification and Characterization of gtf, norB, and trx Genes in Flavobacterium Columnare

Three genes from a shotgun genomic library of Flavobacterium columnare virulent strain ALG-00-530 were identified, characterized, and selected for differential expression analysis based on sequence similarity to putative virulence genes from related species. These genes were: glycosyltransferase (gtf), nitric oxide reductase (norB) and thioredoxin (trx). A collection of 30 F. columnare strains, including strains from genomovars I and II, were tested for the presence of these genes. Distribution patterns of gtf, norB, and trx across the species were not uniform. Nucleotide sequence variation was observed between genomovars for each gene; however, strains within the same genomovar shared identical gene sequences. Nine strains of F. columnare, from both genomovars, were chosen for gene expression analysis. The expression profile of these genes varied when selected strains were grown in vitro under identical conditions. ALG-00-530, a high virulent strain, was chosen for gene expression comparison under standard growing conditions, iron-limited conditions and in the presence of skin explants from channel catfish. NorB, and trx gene expression levels varied when ALG- 00-530 was incubated under different conditions.