# Secretome Profiling of Lactiplantibacillus plantarum CRL681 Predicts Potential Molecular Mechanisms Involved in the Antimicrobial Activity Against Escherichia coli O157:H7

## TL;DR

This study identifies proteins in Lactiplantibacillus plantarum CRL681 that may help it fight Escherichia coli O157:H7, suggesting it could be a useful probiotic.

## Contribution

The study provides a detailed secretome profile of L. plantarum CRL681 and identifies potential antimicrobial mechanisms against E. coli O157:H7.

## Key findings

- The secretome of L. plantarum CRL681 includes proteins involved in cell surface remodeling, metabolism, and stress response.
- Co-culture with E. coli O157:H7 induces changes in proteins related to energy metabolism and transport systems.
- Peptidoglycan hydrolases and ribosomal proteins with antimicrobial activity were identified in the secretome.

## Abstract

Background/Objectives. Lactiplantibacillus plantarum CRL681 has previously demonstrated a strong antagonistic effect against Escherichia coli O157:H7 in food matrices; however, the molecular mechanisms underlying this activity remain poorly understood. Since initial interactions between beneficial bacteria and pathogens occur mainly at the cell surface and in the extracellular environment, the characterization of the bacterial secretome is essential for elucidating these mechanisms. In this study, the secretome of L. plantarum CRL681 was comprehensively characterized using an integrated in silico and in vitro approach. Methods. The exoproteome and surfaceome were analyzed by LC-MS/MS under pure culture conditions and during co-culture with E. coli O157:H7. Identified proteins were functionally annotated, classified according to subcellular localization and secretion pathways, and evaluated through protein–protein interaction network analysis. Results. A total of 275 proteins were proposed as components of the CRL681 secretome, including proteins involved in cell surface remodeling, metabolism and nutrient transport, stress response, adhesion, and genetic information processing. Co-culture with EHEC induced significant changes in the expression of proteins associated with energy metabolism, transport systems, and redox homeostasis, indicating a metabolic and physiological adaptation of L. plantarum CRL681 under competitive conditions. Notably, several peptidoglycan hydrolases, ribosomal proteins with reported antimicrobial activity, and moonlighting proteins related to adhesion were identified. Conclusions. Overall, these findings suggest that the antagonistic activity of L. plantarum CRL681 against E. coli O157:H7 would be mediated by synergistic mechanisms involving metabolic adaptation, stress resistance, surface adhesion, and the production of non-bacteriocin antimicrobial proteins, supporting its potential application as a bioprotective and functional probiotic strain.