Bacillus subtilis natto Derivatives Inhibit Enterococcal Biofilm Formation via Restructuring of the Cell Envelope

Abstract

Enterococcus faecalis is considered a leading cause of hospital-acquired infections. Treatment of these infections has become a major challenge for clinicians because some E. faecalis strains are resistant to multiple clinically used antibiotics. Moreover, the presence of E. faecalis biofilms can make infections with E. faecalis more difficult to eradicate with current antibiotic therapies. Thus, our aim in this study was to investigate the effects of probiotic derivatives against E. faecalis biofilm formation. Bacillus subtilis natto is a probiotic strain isolated from Japanese fermented soybean foods, and its culture fluid potently inhibited adherence to Caco-2 cell monolayers, aggregation, and biofilm production without inhibiting the growth of E. faecalis. An apparent decrease in the thickness of E. faecalis biofilms was observed through confocal laser scanning microscopy. In addition, exopolysaccharide synthesis in E. faecalis biofilms was reduced by B. subtilis natto culture fluid treatment. Carbohydrate composition analysis also showed that carbohydrates in the E. faecalis cell envelope were restructured. Furthermore, transcriptome sequencing revealed that the culture fluid of B. subtilis natto downregulated the transcription of genes involved in the WalK/WalR two-component system, peptidoglycan biosynthesis and membrane glycolipid biosynthesis, which are all crucial for E. faecalis cell envelope synthesis and biofilm formation. Collectively, our work shows that some derivatives present in the culture fluid of B. subtilis natto may be useful for controlling E. faecalis biofilms.

Natto: A medicinal and edible food with health function

“…Among them, Bacillus subtilis natto, as a sort of the most important probiotics, have shown obvious antibacterial activity. Researches have shown the inhibitory effect of B. subtilis natto derivatives on Enterococcus faecalis that is considered to be the leading cause of hospital-acquired infections ( Lin et al, 2021 ). Some derivatives from the culture fluid of B. subtilis natto may be useful for controlling E. faecalis biofilms.…”

In Silico Safety Assessment of Bacillus Isolated from Polish Bee Pollen and Bee Bread as Novel Probiotic Candidates

“…Bacillus spp. are Gram-positive and spore-forming bacteria commonly found in soil and plants, have the advantage of being highly stable in acidic environments, and can thrive in various food matrices [ 40 , 41 , 42 , 43 , 44 ]. In our earlier study, we assessed ten bacterial isolates obtained from bee bread (BB) and bee pollen (BP) to determine their potential as probiotics.…”

A Systematic Comparative Study on the Physicochemical Properties, Volatile Compounds, and Biological Activity of Typical Fermented Soy Foods

“…Multiple studies have shown that FSFs can significantly alleviate hyperlipidemia and lower the likelihood of developing atherosclerosis and cardiovascular pathologies [14]. The Bacillus subtilis natto derivatives exhibit a significant inhibitory effect towards Enterococcus faecalis, which is recognized as a major etiology of nosocomial infections [15]. Yang et al examined Lactococcus acidophilus fermented soymilk and found that the FSFs showed significantly higher antioxidant activity than non-fermented products [16].…”