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. 2022 Sep 6;14(18):3679.
doi: 10.3390/nu14183679.

Surface Layer Protein Pattern of Levilactobacillus brevis Strains Investigated by Proteomics

Maria Fiorella Mazzeo  1 , Anna Reale  1 , Tiziana Di Renzo  1 , Rosa Anna Siciliano  1
Affiliations

Surface Layer Protein Pattern of Levilactobacillus brevis Strains Investigated by Proteomics

Maria Fiorella Mazzeo et al. Nutrients. .

Abstract

The outermost constituent of many bacterial cells is represented by an S-layer, i.e., a semiporous lattice-like layer composed of self-assembling protein subunits called S-layer proteins (Slps). These proteins are involved in several processes, such as protecting against environmental stresses, mediating bacterial adhesion to host cells, and modulating gut immune response. Slps may also act as a scaffold for the external display of additional cell surface proteins also named S-layer associated proteins (SLAPs). Levilactobacillus brevis is an S-layer forming lactic acid bacterium present in many different environments, such as sourdough, milk, cheese, and the intestinal tract of humans and animals. This microorganism exhibits probiotic features including the inhibition of bacterial infection and the improvement of human immune function. The potential role of Slps in its probiotic and biotechnological features was documented. A shotgun proteomic approach was applied to identify in a single experiment both the Slps and the SLAPs pattern of five different L. brevis strains isolated from traditional sourdoughs of the Southern Italian region. This study reveals that these closely related strains expressed a specific pattern of surface proteins, possibly affecting their peculiar properties.

Keywords: L. brevis; lactic acid bacteria; probiotics; proteomics; surface associated proteins; surface layer proteins.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Flow chart of the experimental design. Surface layer proteins (Slps) are indicated with blue triangles and surface layer associated proteins (SLAPs) with green circles.
Figure 2
Figure 2
Heatmap obtained reporting protein abundance (LFQ values) of each surface layer protein (Slp) in technical and biological replicates of each strain. The green and red color ranges refer to the lower and higher abundance, respectively (heat maps were obtained by Perseus).
Figure 3
Figure 3
Relative distribution of the Slps identified in each L. brevis strain.
Figure 4
Figure 4
Venn diagram summarizing proteomic results. Lists including the accession of proteins reliably identified in each strain were used to build the diagram. The number of surface layer associated proteins (SLAPs) present in each strain is reported in bracket.
Figure 5
Figure 5
Dendrogram showing the similarity among RAPD-PCR profiles of L. brevis strains. The red line indicates the cluster cut-off value of 85%, which delimitates the main clusters.
See this image and copyright information in PMC

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