Identification of chemotaxis operon cheYZA and cheA gene expression under stressful conditions in Piscirickettsia salmonis

- The salmon pathogen P. salmonis contained the cheYZA operon.
- P. salmonis AUSTRAL-005 produced higher biofilm levels than LF-89 type strain.
- The cheA transcript levels increased when P. salmonis was grown in liquid medium.

Piscirickettsia salmonis is the etiological agent of piscirickettsiosis, which, as the main systemic disease in the Chilean salmon industry, causes significant economic losses. This bacterium can produce biofilm as a persistence and survival strategy in adverse conditions. In other bacteria, cheA is a key gene for modulating the onset of bacterial chemotaxis, as well as having a secondary role in biofilm production. Notwithstanding this association, the potential relationships between biofilm formation and genes involved in P. salmonis chemotaxis are poorly understood. This study aimed to determine P. salmonis cheA gene expression when grown in different culture media known to induce biofilm production. Piscirickettsia salmonis AUSTRAL-005 produced moderate/high biofilm levels after 144 h of incubation in the AUSTRAL-SRS and marine broths. In contrast, LF-89 biofilm production was weak/nonexistent in the aforementioned broths. Both assessed P. salmonis strains contained the cheYZA operon. Additionally, AUSTRAL-005 cheA transcripts increased in both culture media. In conclusion, these results suggest potential relationships between biofilm formation and genes related to chemotaxis in the fish pathogen P. salmonis.