Transcriptomic Analysis Revealed Antimicrobial Mechanisms of Lactobacillus rhamnosus SCB0119 against Escherichia coli and Staphylococcus aureus.

Lactic acid bacteria were reported as a promising alternative to antibiotics against pathogens. Among them, Lactobacillus rhamnosus could be used as probiotics and inhibit several pathogens, but its antibacterial mechanisms are still less known. Here, L. rhamnosus SCB0119 isolated from fermented pickles could inhibit bacterial growth or even cause cell death in Escherichia coli ATCC25922 and Staphylococcus aureus ATCC6538, which was mainly attributed to the cell-free culture supernatant (CFS). Moreover, CFS induced the accumulation of reactive oxygen species and destroyed the structure of the cell wall and membrane, including the deformation in cell shape and cell wall, the impairment of the integrity of the cell wall and inner membrane, and the increases in outer membrane permeability, the membrane potential, and pH gradient in E. coli and S. aureus. Furthermore, the transcriptomic analysis demonstrated that CFS altered the transcripts of several genes involved in fatty acid degradation, ion transport, and the biosynthesis of amino acids in E. coli, and fatty acid degradation, protein synthesis, DNA replication, and ATP hydrolysis in S. aureus, which are important for bacterial survival and growth. In conclusion, L. rhamnosus SCB0119 and its CFS could be used as a biocontrol agent against E. coli and S. aureus.

Polyhydroxylated sterols from Monascus purpureus-fermented rice.

Using a cell-based cytotoxicity assay, two new polyhydroxylated sterols, 16(S),22(S)-epoxy-3ß,5α,6ß,20(R),23(R),25-hexahydroxy-7-ergostene and 3ß,7ß,8α,25-tetrahydroxy-5,22E-ergostadiene were isolated from the ethyl acetate portion of the ethanolic extract of Monascus purpureus. Their structures were elucidated by spectroscopic analysis and in comparison with those reported in the literature. Both compounds showed cytotoxic activity against the lung adenocarcinoma (A549) with IC50 values of 12.6 and 18.5 µM, exhibited moderate activities against human ovarian cancer (A2780), with IC50 values of 8.8 and 9.4 µM.