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Comparative Analysis of Membrane Vesicles from Three Piscirickettsia salmonis Isolates Reveals Differences in Vesicle
Julia I Tandberg1,2, Leidy X Lagos1,2, Petter Langlete1,2
1Center of Integrative Microbiology and Evolution, University of Oslo, Oslo, Norway.
Abstract:
Membrane vesicles (MVs) are spherical particles naturally released from the membrane of Gram-negative bacteria. Bacterial MV production is associated with a range of phenotypes including biofilm formation, horizontal gene transfer, toxin delivery, modulation of host immune responses and virulence. This study reports comparative profiling of MVs from bacterial strains isolated from three widely disperse geographical areas. Mass spectrometry identified 119, 159 and 142 proteins in MVs from three different strains of Piscirickettsia salmonis isolated from salmonids in Chile (LF-89), Norway (NVI 5692) and Canada (NVI 5892), respectively. MV comparison revealed several strain-specific differences related to higher virulence capability for LF-89 MVs, both in vivo and in vitro, and stronger similarities between the NVI 5692 and NVI 5892 MV proteome. The MVs were similar in size and appearance as analyzed by electron microscopy and dynamic light scattering. The MVs from all three strains were internalized by both commercial and primary immune cell cultures, which suggest a potential role of the MVs in the bacterium's utilization of leukocytes. When MVs were injected into an adult zebrafish infection model, an upregulation of several pro-inflammatory genes were observed in spleen and kidney, indicating a modulating effect on the immune system. The present study is the first comparative analysis of P. salmonis derived MVs, highlighting strain-specific vesicle characteristics. The results further illustrate that the MV proteome from one bacterial strain is not representative of all bacterial strains within one species.
Insights
Bacterial membrane vesicles (MVs) from Piscirickettsia salmonis strains show distinct protein profiles and virulence. These MVs are internalized by immune cells and modulate host immune responses, highlighting strain-specific characteristics.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Proteomics
Background:
- Membrane vesicles (MVs) are released by Gram-negative bacteria and play roles in virulence, gene transfer, and immune modulation.
- Piscirickettsia salmonis is a significant pathogen affecting salmonid aquaculture.
- Comparative analysis of MVs from different geographical isolates is crucial for understanding bacterial adaptation and virulence.
Purpose of the Study:
- To comparatively profile membrane vesicles (MVs) from three distinct Piscirickettsia salmonis strains isolated from different geographical regions.
- To investigate strain-specific differences in MV protein composition and their implications for virulence.
- To assess the interaction of MVs with host immune cells and their effect on immune gene expression.
Main Methods:
- Proteomic analysis using mass spectrometry to identify proteins in MVs.
- Electron microscopy and dynamic light scattering for MV size and morphology assessment.
- In vitro studies with immune cell cultures and in vivo studies using an adult zebrafish infection model.
Main Results:
- Identified 119, 159, and 142 proteins in MVs from Chilean, Norwegian, and Canadian P. salmonis strains, respectively.
- LF-89 MVs exhibited higher in vitro and in vivo virulence compared to other strains.
- MVs were internalized by immune cells, and their injection induced pro-inflammatory gene upregulation in zebrafish.
Conclusions:
- Piscirickettsia salmonis MVs display significant strain-specific proteomic differences and varying virulence.
- MVs are involved in host-pathogen interactions, including immune cell uptake and modulation of immune responses.
- The MV proteome is not conserved across all strains within a bacterial species, emphasizing the need for strain-specific investigations.
