Abstract: Edwardsiella piscicida is a major pathogen of marine fish in aquaculture, leading to severe economic loss. The mechanisms underline E. piscicida infection is yet to be fully understood. In our previous work, we identified multiple sRNAs with differential transcription levels under various conditions, including a sRNA termed sR082. The present study analyzed the transcription levels of sR082 of E. piscicida strain TXD1 upon acid stress. Further, with a sR082 knock-out strain designated TXΔsR082, we investigated the impacts of sR082 on the infective capacities to fish cell line, tissues and individuals, respectively. The results indicated that the transcription of sRNA was significantly upregulated under acidic condition. Compared to TXD1, the mutant strain TXΔsR082 exhibited significantly lower capacities on infecting and replicating in flounder FG cells, decreased dissemination in multiple flounder tissues, and attenuated lethality to fish. These observations suggested that sR082 likely plays important roles in response to acid stress and virulence of E. piscicida.

Key words: Edwardsiella piscicida, small non-coding RNA, acid stress, virulence