Phenotypic and genomic characterization of a strain causing disease in provides insights into its niche adaptation and pathogenic mechanism.

The virulence of is variable depending on its virulence determinants. A strain, in which the virulence is governed by the and genes, can cause acute hepatopancreatic necrosis disease (AHPND) in shrimps. Some that are non-AHPND strains also cause shrimp diseases and result in huge economic losses, while their pathogenicity and pathogenesis remain unclear. In this study, a non-AHPND , TJA114, was isolated from diseased associated with a high mortality. To understand its virulence and adaptation to the external environment, whole-genome sequencing of this isolate was conducted, and its phenotypic profiles including pathogenicity, growth characteristics and nutritional requirements were investigated. Shrimps following artificial infection with this isolate presented similar clinical symptoms to the naturally diseased ones and generated obvious pathological lesions. The growth characteristics indicated that the isolate TJA114 could grow well under different salinity (10-55 p.p.t.), temperature (23-37 °C) and pH (6-10) conditions. Phenotype MicroArray results showed that this isolate could utilize a variety of carbon sources, amino acids and a range of substrates to help itself adapt to the high hyperosmotic and alkaline environments. Antimicrobial-susceptibility test showed that it was a multidrug-resistant bacterium. The whole-genomic analysis showed that this possessed many important functional genes associated with multidrug resistance, stress response, adhesions, haemolysis, putative secreted proteases, dedicated protein secretion systems and a variety of nutritional metabolic mechanisms. These annotated functional genes were confirmed by the phenotypic profiles. The results in this study indicated that this isolate possesses a high pathogenicity and strong environmental adaptability.