Project description:Aliivibrio (Vibrio) salmonicida is the causative agent of cold-water vibriosis in salmonids (Oncorhynchus mykiss and Salmo salar L.) and gadidae (Gadus morhua L.). Virulence-associated factors that are essential for the full spectrum of Al. salmonicida pathogenicity are largely unknown. Chitin-active lytic polysaccharide monooxygenases (LPMOs) have been indicated to play roles in both chitin degradation and virulence in a variety of pathogenic bacteria. In the present study we investigated the role of LPMOs in the pathogenicity of Al. salmonicida LFI238 in Atlantic salmon (Salmo salar L.). In vivo challenge experiments using isogenic deletion mutants of the two LPMOs encoding genes AsLPMO10A and AsLPMO10B, showed that both LPMOs, and in particular AsLPMO10B, were important in the invasive phase of cold-water vibriosis. Crystallographic analysis of the AsLPMO10B AA10 LPMO domain (to 1.4 Å resolution) revealed high structural similarity to viral fusolin, an LPMO known to enhance the virulence of insecticidal agents. Finally, exposure to Atlantic salmon serum resulted in substantial proteome re-organization of the Al. salmonicida LPMO deletion variants compared to the wild type strain, indicating the struggle of the bacterium to adapt to the host immune components.
Project description:Aliivibrio salmonicida causes “cold-water vibriosis” (or “Hitra disease”) in fish, including marine-reared Atlantic salmon. During development of the disease the bacterium will encounter macrophages with antibacterial activities such as production of damaging reactive oxygen species (ROS). To defend itself the bacterium will presumably start producing detoxifying enzymes, reducing agents, and proteins involved in DNA and protein repair systems. Even though responses to oxidative stress are well studied for a few model bacteria, little work has been done in general to explain how important groups of pathogens, like members of the Vibrionaceae family, can survive at high levels of ROS. We have used bioinformatic tools and an –omics approach to study how A. salmonicida responds to hydrogen peroxide (H2O2). First, we used the recently published genome sequence to predict potential binding sites for OxyR (H2O2 response regulator). The computer-based search identified OxyR sites associated with 20 single genes and 8 operons, and these predictions were compared to experimental data from Northern blot analysis, microarray analysis and 2D gel electrophoresis. In general, OxyR binding site predictions and experimental results are in agreement. Up- and down-regulated genes are distributed among all functional gene categories, but a striking number of ≥2 fold up-regulated genes encode proteins involved in detoxification or DNA protection and repair, are part of reduction systems, or are involved in carbon metabolism and regeneration of NADH/NADPH. Our predictions and –omics data corroborates well with findings from other model bacteria, but also suggest species-specific gene regulation.
Project description:Prediction, microarray and Northern blot analyses identify new intergenic small RNAs in Aliivibrio salmonicida (LB medium vs. iron-limited condition)
Project description:Prediction, microarray and Northern blot analyses identify new intergenic small RNAs in Aliivibrio salmonicida (wild type vs. LitR mutant)
Project description:Expression profiling of a spf deletion mutant suggests biological roles and mRNA targets for Spot 42 in the fish pathogen Aliivibrio salmonicida
Project description:Responses of salmonid populations to ecosystem degradation often, if not typically, involve multiple stressors. The interaction of disease and contaminant exposure is of potential relevance to persistence of salmonid populations. The duration of PAH exposure and the life stage of exposure in the trout reflect a likely exposure scenario for some stocks of anadromous salmonids (sub-yearling ocean-type Chinook salmon) during emigration to the ocean. This current study focuses on the genes expressed in rainbow trout after exposure to both the high molecular weight PAH mixture and to the A. salmonicida pathogen.
