, the etiological agent of columnaris disease, is one of the most important bacterial pathogens of freshwater fish in the world. However, suitable genetic manipulation of this bacterium which has been challenging and producing genetic mutations in this bacterium has not been reported. Therefore, isolation of an effective promoter in may provide tools for the development of a genetic manipulation system in the bacterium. In this study,) and flanking sequences were analyzed to determine promoter function. The gene is 2 323 bp long, encoding a protein of 635 amino acids. A TAAAA motif was identified as the conserved sequence for ribosome binding site (RBS) and TATTTTCG and TTG were determined to be –7 and –33 promoter motifs, upstream of the upstream regulation sequence () gene and was introduced into strain, the host cells gained ) resistance. was both determined to be T locating 46 bp upstream of the start codon. Deletion analysis of the promoter showed that at least 164 bp nucleotides upstream of the start codon were required for promoter activity and for the expression of CAT. Nucleotide analysis and alignment of the putative RBS for 32 protein-coding genes in conserved RBS consensus, TAAAA, in. The current study described the first successful construction of a plasmid that was able to express cloned genes in , which will allow further studies of the important columnaris disease in fish.