Proteome analysis of the Gram-positive fish pathogen Renibacterium salmoninarum reveals putative role of membrane vesicles in virulence

Tobias Kroniger,Anke Trautwein-Schult,Daniel Flender,Dörte Becher,Bernd Köllner,Rabea Schlüter

doi:10.1038/s41598-022-06130-w

Tobias Kroniger, Anke Trautwein-Schult + Show 4 more

Open Access

https://doi.org/10.1038/s41598-022-06130-w

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Abstract

Bacterial kidney disease (BKD) is a chronic bacterial disease affecting both wild and farmed salmonids. The causative agent for BKD is the Gram-positive fish pathogen Renibacterium salmoninarum. As treatment and prevention of BKD have proven to be difficult, it is important to know and identify the key bacterial proteins that interact with the host. We used subcellular fractionation to report semi-quantitative data for the cytosolic, membrane, extracellular, and membrane vesicle (MV) proteome of R. salmoninarum. These data can aid as a backbone for more targeted experiments regarding the development of new drugs for the treatment of BKD. Further analysis was focused on the MV proteome, where both major immunosuppressive proteins P57/Msa and P22 and proteins involved in bacterial adhesion were found in high abundance. Interestingly, the P22 protein was relatively enriched only in the extracellular and MV fraction, implicating that MVs may play a role in host–pathogen interaction. Compared to the other subcellular fractions, the MVs were also relatively enriched in lipoproteins and all four cell wall hydrolases belonging to the New Lipoprotein C/Protein of 60 kDa (NlpC/P60) family were detected, suggesting an involvement in the formation of the MVs.

Highlights

Pathway or the more dedicated type I-V protein secretion s ystems[18], proteins can be secreted via bacterial membrane vesicles (MVs)
While the mechanism behind the formation of MVs in Gram-positive bacteria is not fully understood, proteins involved in cell wall modification, like transpeptidases and autolysins are hypothesized to play an important role in the formation process, as these proteins have been detected in MVs released from Gram-positive b acteria[20,21,22]
A principal component analysis (PCA) of the label-free quantification (LFQ) intensities revealed a distinct differentiation between the four enriched subcellular fractions and a high reproducibility between the replicates within the respective fractions (Fig. 1a)

Summary

Introduction

Pathway or the more dedicated type I-V protein secretion s ystems[18], proteins can be secreted via bacterial membrane vesicles (MVs). While the mechanism behind the formation of MVs in Gram-positive bacteria is not fully understood, proteins involved in cell wall modification, like transpeptidases and autolysins are hypothesized to play an important role in the formation process, as these proteins have been detected in MVs released from Gram-positive b acteria[20,21,22]. An extensive subcellular fraction of R. salmoninarum was performed to yield a comprehensive proteomic dataset which includes semi-quantitative data of the cytosolic, the membrane, and the extracellular subproteome as well as the subproteome of R. salmoninarum MVs. The global investigation of the most abundant proteins in different subcellular localizations may provide insight for vaccine or drug development research and give hints regarding the biogenesis of MVs in R. salmoninarum or in Gram-positive bacteria in general

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