Antimicrobial activity against Staphylococcus aureus and genome features of Lactiplantibacillus plantarum LR-14 from Sichuan pickles.

The persistence of Staphylococcus aureus within biofilm can lead to contamination of medical devices and life-threatening infections. Luckily, lactic acid bacteria (LAB) have an inhibitory effect on the growth of these bacteria. This study aims to select LAB strains from fermented vegetables, and analyze their potential inhibition activities against S. aureus. In total, 45 isolates of LAB were successfully isolated from Sichuan pickles, and the CFS of Lactiplantibacillus plantarum LR-14 exerted the strongest inhibitory effect against S. aureus. Moreover, S. aureus cells in planktonic and biofilm states both wrinkled and damaged when treated with the CFS of L. plantarum LR-14. In addition, whole genome sequencing analysis indicates that L. plantarum LR-14 contains various functional genes, including predicted extracellular polysaccharides (EPS) biosynthesis genes, and genes participating in the synthesis and metabolism of fatty acid, implying that L. plantarum LR-14 has the potential to be used as a probiotic with multiple functions.

Isolation and characterization of bacteria that produce quorum sensing molecules during the fermentation and deterioration of pickles.

Pickles are typical traditional Chinese fermented vegetables. Complex microbiota interacts throughout the fermentation and deterioration process. Minimal studies are available involving quorum sensing (QS) signaling in pickles. This study investigated the changes in the general pickle properties and microbial diversity at 4 d, 31 d, and 79 d. The QS signaling activity of various strains isolated at these key time points was screened using biosensor strains, while the types of signal molecules were further identified using UHPLC/QTOF-MS/MS. At 4 d, Lactobacillus represented the dominant genus, while Lactobacillus plantarum was identified as the bacteria with AI-2-producing ability. At 31 d, the dominant genus was also Lactobacillus, while the relative abundance of Pediococcus displayed a distinct increase. At this time point, L. plantarum represented the AI-2-producing bacteria, followed by Lactobacillus brevis, Pediococcus sp., Enterobacter sp., and Bacillus megaterium. At 79 d, Lactobacillus was displaced by Enterobacter as the dominant microorganisms, while the AI-2-producing bacteria were identified as L. plantarum, Enterobacter sp., B. megaterium, Klebsiella sp., and Staphylococcus sp. Moreover, AHL activity was only present in isolates from the 79-d brine and was identified as C4-HSL and C6-HSL. In addition, the luxS gene was amplified via cDNA reversely transcription from the total RNA extracted from the brine at all three time points using the L. plantarum luxS primers. The AHL-related genes were only amplified in the RNA of 79-d brine samples using Klebsiella pneumoniae- and Bacillus cereus-related primers. This study presented theoretical references for QS during pickle fermentation and deterioration.

Metabolic profiles of Lactobacillus paraplantarum in biofilm and planktonic states and investigation of its intestinal modulation and immunoregulation in dogs.

The use of probiotics has recently become a considerably promising research area. The most advanced fourth-generation probiotics involve beneficial bacteria enclosed in biofilms. However, differences in the effects of probiotics in biofilm and those in planktonic states are, as yet, unclear. In this study, it was ascertained that the biofilm mode of Lactobacillus paraplantarum L-ZS9 had a comparatively higher density and stronger resistance. Untargeted metabolomics analysis suggested a significant distinction between planktonic and biofilm cells, with amino acids and carbohydrate metabolism both more active in the biofilm mode. Furthermore, the in vivo experiment showed that the biofilm strain displayed better immunomodulation activity, which could increase the relative abundance of Lactobacillus in the intestinal microbiota of dogs. The relative abundance of intestinal microbiota participating in carbohydrate metabolism was higher in the biofilm probiotic-treated dogs. Correlation analysis between L-ZS9-producing metabolites, dog intestinal microbiome diversity and dog blood immune indexes (sIgA or IgG) revealed the interaction between these three components, which might explain the mechanisms by which biofilm L-ZS9 regulated the intestinal microbiome and immunity activity of the host, through the production of various metabolites. Findings of this study will, thus, enhance understanding of the beneficial effects of biofilm probiotics, as well as provide references for further investigation.