Genome Characterization Of Hahella Chejuensis Strain Hn01, A Pathogen Of Red Egg Disease In Tilapia (Oreochromis Sp.)

Abstract

Red eggs disease is an emerging disease occurred in Tilapia hatcheries which caused by a Gram-negative bacterium called Hahella chejuensis HN01. The disease infects to all the stage of fish eggs and reduces the hatchability. However, there are limited study about the bacterial pathogenicity. In this study, we analyzed the phylogenetic relationship and characterized the virulence traits of Hahella chejuensis by using genomic approach. The bacterial genome was sequenced using Illumina Miseq platform. The phylogenetic tree based on several housekeeping genes confirmed that the bacterium was belong to Genus Hahella and species chejuensis. the Average Nucleotide Identity calculation with the reference strain, Hahella chejuensis KCTC2396 was 89.40% which still indicates the variability between two genomes. The annotation against the Virulence Factor Data Base revealed the genome of Hahella chejuensis HN01 specifically harbors 19 virulence genes contributed to capsules, pigments, adhesion proteins, enzymes, toxins, and secretion system productions. Interestingly, two genes highly similar to toxin genes in Vibrio cholerae; cholera enterotoxin (ctxA) and zona occludens toxin (zot), were found exclusively in the strain HN01. This study brings a new insight in preliminary exploring the genotypic virulence properties of Hahella chejuensis HN01.