Identification of proteins involved in the anti-inflammatory properties of Propionibacterium freudenreichii by means of a multi-strain study
Résumé
Propionibacterium freudenreichii, a dairy starter, can reach a population of almost 109 propionibacteria
per gram in Swiss-type cheese at the time of consumption. Also consumed as a probiotic, it displays
strain-dependent anti-inflammatory properties mediated by surface proteins that induce IL-10 in
leukocytes. We selected 23 strains with varied anti-inflammatory potentials in order to identify the
protein(s) involved. After comparative genomic analysis, 12 of these strains were further analysed by
surface proteomics, eight of them being further submitted to transcriptomics. The omics data were
then correlated to the anti-inflammatory potential evaluated by IL-10 induction. This comparative
omics strategy highlighted candidate genes that were further subjected to gene-inactivation
validation. This validation confirmed the contribution of surface proteins, including SlpB and SlpE, two
proteins with SLH domains known to mediate non-covalent anchorage to the cell-wall. Interestingly,
HsdM3, predicted as cytoplasmic and involved in DNA modification, was shown to contribute to
anti-inflammatory activity. Finally, we demonstrated that a single protein cannot explain the antiinflammatory
properties of a strain. These properties therefore result from different combinations
of surface and cytoplasmic proteins, depending on the strain. Our enhanced understanding of the
molecular bases for immunomodulation will enable the relevant screening for bacterial resources with
anti-inflammatory properties.
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