Label-free quantitative proteomic analysis of the inhibition effect of Lactobacillus rhamnosus GG on Escherich coli biofilm formation in coculture

Abstract

Background: Escherich coli (E.coli) is the principal pathogen that causes biofilm formation; the latter is associated with infectious diseases and antibiotic resistance. In our previous work, we demonstrated that probiotic microcapsules have superior biofilm inhibition capacity compared to probiotic sterile culture supernatant. Herein, the mechanism of the inhibition effects was investigated using label-free quantitative proteomics analysis. Results:The proteomic analysis characterized a total of 1655 proteins in E.coli K12MG1655 and 1431 proteins in Lactobacillus rhamnosus GG (LGG). Among them, after coculture treatment, there were 262 and differentially expressed proteins that were specific for E.coli and 291 for LGG. The differentially expressed proteins after coculture were related to cellular metabolism, the stress response, transcription, and the cell membrane. In addition, we identified five strain-specific genes in E.coli and LGG, respectively, which were consistent with the proteomics results. Conclusions:These findings indicate that LGG microcapsules may inhibit E.coli biofilm inhibition by disrupting metabolic processes, particularly in relation to energy metabolism and stimulus responses, both of which are critical for the growth of LGG. Together, these findings increase our understanding of the interactions between bacteria under coculture conditions. BackgroundBiofilms are complex bacterial community structures that can attach to a surface. They are connected to this surface via extracellular polymeric substances (EPS) which form a matrix composed primarily of polysaccharides, proteins, and DNA; this encapsulates the bacteria [1]. Biofilms not only cause economic losses, but also present a public health hazard. This is because the bacteria present within biofilms are much more resistant to antibiotics, disinfectants [2], and the host immune system effectors [3]. Therefore, it is critical to uncover effective non-toxic, or less toxic, antifungal agents with novel modes of action.A recent study suggested that probiotic supernatants have antipathogenic properties [4], which implies that probiotics may inhibit biofilm formation through cell-cell communication. However, there