AHL-mediated quorum sensing regulation: Role in controlling cytotoxicity, T6SSs and CRISPR-Cas systems in Aliivibrio wodanis

• Main Author: Maharajan, Amudha Deepalakshmi
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: UiT Norges arktiske universitet 2023
• Subjects: VDP::Mathematics and natural science: 400::Basic biosciences: 470::General microbiology: 472; VDP::Matematikk og Naturvitenskap: 400::Basale biofag: 470::Generell mikrobiologi: 472; VDP::Agriculture and fishery disciplines: 900::Clinical veterinary science disciplines: 950; VDP::Landbruks- og Fiskerifag: 900::Klinisk veterinærmedisinske fag: 950; DOKTOR-004; Atlantic salmon
• Online Access: https://hdl.handle.net/10037/28075

Aliivibrio wodanis has been associated with winter ulcer disease outbreaks. It has been reported that A. wodanis may act as a secondary pathogen in disease outbreaks and pathogenesis. The culture supernatant of A. wodanis causes a cytopathogenic effect (CPE) in various salmon cell lines. Moreover, in an Atlantic salmon bath challenge experiment, A. wodanis alone produces clinical symptoms in the fish. However, the contribution of A. wodanis to winter ulcer disease is not clear. Despite the knowledge to date and the research done in the field, there are still unanswered questions and a knowledge gap. Several Vibrio and Aliivibrio species use quorum sensing (QS) to regulate genes connected to host-pathogen interaction, virulence, survival, and adaptation mechanisms. In other aliivibrios, several QS systems, including the ainS /AinR and a transcriptional regulator litR (LuxR homologs), have been reported to regulate various phenotypic traits. Moreover, temperature is an essential factor that governs the prevalence of bacteria in the environment and host and is a potent regulator of pathogenesis in many bacteria. Hence the thesis aimed to understand better the QS`s role and the effect of temperature in A. wodanis . Our study reveals that ainS autoinducer synthase is required to produce the Acyl-Homoserine Lactone (AHL) 3OHC10-HSL in A. wodanis . Furthermore, we found that the 3OHC10-HSL production is cell density and temperature-dependent. The 3OHC10-HSL concentration was higher at 6°C, the temperature below the threshold temperature at which winter ulcer occurs, compared to 12°C. The results also showed that QS and temperature regulate various functions such as AHL production, motility, and production of proteases, hemolysin and siderophores. The cell culture study further revealed that cell density, QS and temperature influence the cytotoxicity in CHSE salmon cell lines. This suggests that A. wodanis produces cytolysins and cytotoxins that are implicated in cytotoxicity. Bacteria use the Type VI secretion system ...