Previously, we reported that metronidazole MICs are not dependent on the expression levels of nim genes in B. fragilis strains; and we also compared the proteomes of metronidazole-resistant laboratory B. fragilis strains to those of their susceptible parent strains. Here, we used RT-qPCR to correlate the expression levels of 18 candidate genes in a panel of selected, clinical nim gene-positive and -negative B. fragilis strains to their metronidazole MICs. Metronidazole MICs were correlated to the expression of certain tested genes. Specifically, lactate dehydrogenase expression correlated positively, whereas cytochrome fumarate reductase/succinate dehydrogenase, malate dehydrogenase, phosphoglycerate kinase redox and gat (GCN5-like acetyltransferase), and relA (stringent response) regulatory gene expressions correlated negatively with metronidazole MICs. This result provides evidence for the involvement of carbohydrate catabolic enzymes in metronidazole resistance in B. fragilis. This result was supported by direct substrate utilization tests. However, the exact roles of these genes/proteins should be determined in deletion–complementation tests. Moreover, the exact redox cofactor(s) participating in metronidazole activation need to be identified.

Increasing clinical and preclinical evidences implicate gut microbiome (GM) dysbiosis as a key susceptibility factor for neurodegenerative disorders, including Alzheimer’s disease (AD) and Parkinson’s diseases (PD). In recent years, neurodegenerative diseases have not been viewed as driven solely by defects in brain, and the role of GM in modulating the central nervous system function via gut-brain axis has attracted considerable interest. Encouraged by GM researches, the next-generation probiotics may lead to tangible impacts on the treatment of neurodegenerative disorders. This review summarizes the current understandings of GM composition and characteristics associated with neurodegenerative diseases, and the demonstrations of molecules from GM affecting neurodegeneration. Particularly, applications of next-generation probiotics such as Clostridium butyricum, Akkermansia muciniphila, Faecalibacterium prausnitzii, and Bacteroides fragilis for remediation of neurodegenerative diseases are discussed.

Carrot juice and its associated beverage products are well-known healthy drinks all over the world. However, what effect carrot juice has on the human gut microbiota and how it is fermented by the intestinal microbes have not been studied. Here, using an in vitro model of anaerobic fermentation, we demonstrated that carrot juice could be fermented into lactate and acetate by the human gut microbiota. 16S high-throughput sequencing and bioinformatic analyses indicated that fermentation of carrot juice could significantly change the composition of the human gut microbiome. Interestingly, carrot juice remarkably increased the abundances of beneficial bacteria, including Lactobacillus fermentum, Lactobacillus salivarius, Lactobacillus mucosae and Bacteroides uniformis and decreased the population of opportunistic pathogenic bacteria, such as Enterococcus faecium in the gut. Collectively, our study illustrates a favorable effect of carrot juice on the human gut microbiota and lays a foundation for the development of carrot juice as a novel prebiotic agent.