Role and interaction of bacterial sphingolipids in human health.

Sphingolipids, present in both higher animals and prokaryotes, involving in cell differentiation, pathogenesis and apoptosis in human physiological health. With increasing attention on the gut microbiome and its impact on wellbeing, there is a renewed focus on exploring bacterial sphingolipids. This review aims to consolidate the current understanding of bacterial sphingolipids and their impact on host health. Compared to mammalian sphingolipids, bacterial sphingolipids are characterized by odd chain lengths due to the presence of branched alkyl chains. Additionally, intestinal microbial sphingolipids can migrate from the gut to various host organs, affecting the immune system and metabolism. Furthermore, the intricate interplay between dietary sphingolipids and the gut microbiota is explored, shedding light on their complex relationship. Despite limited knowledge in this area, this review aims to raise awareness about the importance of bacterial sphingolipids and further our understanding of more uncharacterized bacterial sphingolipids and their significant role in maintaining host health.

Axial Ligand as a Critical Factor for High-Performance Pentagonal Bipyramidal Dy(III) Single-Ion Magnets.

The choice of axial ligands is of great importance for the construction of high-performance Dy-based single-molecule magnets (SMMs). Here, combining axial ligands Ph3SiO- (anion of triphenylsilanol) and 2,6-dichloro-4-nitro-PhO- (the anion of 2,6-dichloro-4-nitrophenol) with a neutral macrocyclic ligand 2,14-dimethyl-3,6,10,13,19-pentaazabicyclo[13.3.1]nonadeca-1(19),2,13,15,17-pentaene (L2N5) generates two new pentagonal bipyramidal Dy(III) complexes [DyIII(L2N5) (X)2](BPh4) (X = Ph3SiO-, 1; 2,6-dichloro-4-nitro-PhO-, 2) with strong axial ligand fields. Magnetic characterizations show that 1 possesses a large energy barrier above 1000 K and a magnetic hysteresis up to 9 K, whereas 2 only displays field-induced peaks of alternating-current susceptibilities without the hysteresis loop, even though 2 has a similar coordination geometry with 1. Detailed Ab initio calculations indicate an apparent difference in the axial negative charge between both complexes, which is caused by the diverse electron-donating properties of the axial ligands. The present work provides an efficient strategy to enhance the SMMs' properties, which highlights that the electron-donating property of the axial ligands is especially important for constructing the high-performance Dy-based SMMs.

Gut Bifidobacterium responses to probiotic Lactobacillus casei Zhang administration vary between subjects from different geographic regions.

Bifidobacteria are health-promoting human gut inhabitants, but accurate species-level composition of the gut bifidobacteria and their responses to probiotic intervention have not been fully explored. This was a follow-up work of our previous study, in which 104 volunteers from six different Asiatic regions (Singapore, Indonesia, Xinjiang, Gansu, Inner Mongolia, Mongolia) were recruited. The gut microbiota and their responses towards Lactobacillus casei Zhang (LCZ) intervention were characterized (at days 0, 7, and 14; 14 days after stopping probiotic intake), and region-based differential responses were observed after LCZ intervention. This study further investigated changes in the species-level gut bifidobacteria by PacBio small-molecule real-time sequencing (SMRT) using bifidobacteria-specific primers. Firstly, this study found that Bifidobacterium adolescentis (42.58%) and Bifidobacterium breve (26.34%) were the core species across the six Asiatic regions. Secondly, principal coordinate analysis of probiotic-induced changes in the gut bifidobacterial microbiota (represented by weighted UniFrac distances) grouped the six regions into two clusters, namely northern (Xinjiang, Gansu, Inner Mongolia, and Mongolia) and southern (Singapore, Indonesia) regions. Thirdly, LCZ intervention induced region-based differential responses of gut bifidobacterial microbiota. The relative abundance of Bifidobacterium animalis in subjects from northern but not southern region substantially increased after LCZ intervention. Moreover, LCZ intervention significantly increased the weighted UniFrac distances in the southern but not northern subjects 7 days after LCZ intervention. The gut B. adolescentis correlated significantly and negatively with the weighted UniFrac distances of the baseline gut bifidobacterial microbiota in subjects of northern but not southern region, suggesting a possible homeostatic effect of LCZ on the gut bifidobacterial population of northern but not southern subjects. Collectively, our study found that probiotic-induced responses of the gut bifidobacterial microbiota varied with subjects' geographic origins, and B. adolescentis might play a role in maintaining the overall stability of the gut bifidobacterial population. KEY POINTS: • The core species in the six Asiatic regions are Bifidobacterium adolescentis and Bifidobacterium breve. • The gut bifidobacterial microbiota in people from various geographic origins showed different responses on probiotic administration.

Differential structures and enterotype-like clusters of Bifidobacterium responses to probiotic fermented milk consumption across subjects using a Bifidobacterium-target procedure.

The health-promoting attributes of bifidobacteria have piqued interest of researchers worldwide. However, scant published studies are available pertinent to bifidobacteria in microbiota/metagenomics datasets due to its intrinsic low abundance and limitations of detection methods. In this work, we designed a procedure to optimize the detection of the bifidobacterial population in complex biological samples with single-molecule real-time sequencing (SMRT) technology, including one primer pair designated as Bif-6 and a Bifidobacterium-specific database. The optimized procedure detected 14 bifidobacterial species/subspecies in ten human stool samples (2024 sequences per sample) and eight breast milk samples (3473 sequences per sample), respectively. Furthermore, by using the optimized procedure of SMRT, we investigated the effect of a 4-week-intervention of probiotic fermented milk (PFM; 200 g/day) on the gut bifidobacteria population of adults. The results showed that consuming PFM changed the structure and enterotype-like clusters of Bifidobacterium. After the consumption of PFM, the level of gut Bifidobacterium animalis increased significantly, replacing several originally dominating taxa in some subjects, including B. catenulatum, B. breve, and B. bifidum. On the other hand, B. adolescentis was, unaffectedly, the representative species in subjects having an original enterotype-like cluster of B. adolescentis. In conclusion, our work designed a procedure for detecting the bifidobacterial population in complex samples. By applying the currently designed procedure, we found that the PFM intervention changed the bifidobacterial enterotype-like cluster of some subjects, and such change was dependent on the basal bifidobacterial population.

Fermented milk containing Lactobacillus casei Zhang and Bifidobacterium animalis ssp. lactis V9 alleviated constipation symptoms through regulation of intestinal microbiota, inflammation, and metabolic pathways.

Studies suggest that probiotics and fermented milk can improve defecation in constipated patients. However, the mechanism of fermented milk containing probiotics on constipation remains poorly understood. Volunteers with chronic constipation symptoms were recruited and given 200 g/d of fermented milk containing Lactobacillus casei Zhang and Bifidobacterium animalis ssp. lactis V9 (PFM) for 4 wk. Clinical symptoms, cytokines, metagenomics, and metabolomics were evaluated in constipated participants before and after PFM intervention. After PFM intervention, we observed significant improvement of constipation symptoms. In the serum samples, the anti-inflammatory cytokine IL-10 increased and the proinflammatory cytokine C-reactive protein and lipopolysaccharides decreased. Metagenomics results showed that the increase of B. animalis was correlated with an increase in defecation frequency. Fatty acid biosynthesis and bile acid biosynthesis in stool samples as well as carnitine shuttle, vitamin E metabolism, and ascorbate and aldarate metabolism were identified as significantly altered metabolic pathways. Acylcarnitine, located on the carnitine shuttle pathway, had a significantly positive correlation with defecation frequency. It was speculated that PFM may contribute to alleviating constipation symptoms through 3 potential mechanisms: fine-tuning gastrointestinal microbiota, fighting inflammation, and regulating metabolic pathways.

Probiotic Bifidobacterium lactis V9 Regulates the Secretion of Sex Hormones in Polycystic Ovary Syndrome Patients through the Gut-Brain Axis.

Although a few studies have investigated the intestinal microbiota of women with polycystic ovary syndrome (PCOS), the functional and metabolic mechanisms of the microbes associated with PCOS, as well as potential microbial biomarkers, have not yet been identified. To address this gap, we designed a two-phase experiment in which we performed shotgun metagenomic sequencing and monitored the metabolic parameters, gut-brain mediators, and sex hormones of PCOS patients. In the first stage, we identified an imbalance in the intestinal microbiota of the PCOS patients, observing that Faecalibacterium, Bifidobacterium, and Blautia were significantly more abundant in the control group, whereas Parabacteroides and Clostridium were enriched in the PCOS group. In the second stage, we monitored the impact of the probiotic Bifidobacterium lactis V9 on the intestinal microbiome, gut-brain mediators, and sex hormones of 14 PCOS patients. Notably, we observed that the levels of luteinizing hormone (LH) and LH/follicle-stimulating hormone (LH/FSH) decreased significantly in 9 volunteers, whereas the levels of sex hormones and intestinal short-chain fatty acids (SCFAs) increased markedly. In contrast, the changes in the indices mentioned above were indistinct in the remaining 5 volunteers. The results of an analysis of the number of viable Bifidobacterium lactis V9 cells in the two groups were highly consistent with the clinical and SCFA results. Therefore, effective host gut colonization of the probiotic Bifidobacterium lactis V9 was crucial for its ability to function as a probiotic. Finally, we propose a potential mechanism describing how probiotics regulate the levels of sex hormones by manipulating the intestinal microbiome in PCOS patients. IMPORTANCE Polycystic ovary syndrome (PCOS) is a common metabolic disorder among women of reproductive age worldwide. Through a two-phase clinical experiment, we first revealed an imbalance in the intestinal microbiome of PCOS patients. By binning and annotating shotgun metagenomic sequences into metagenomic species (MGS), 61 MGSs were identified as potential PCOS-related microbial biomarkers. In the second stage, we monitored the impact of the probiotic Bifidobacterium lactis V9 on the intestinal microbiota, metabolic parameters, gut-brain mediators, and sex hormones of PCOS patients. Notably, we observed that the PCOS-related clinical indices and the intestinal microbiotas of the participating patients exhibited an inconsistent response to the intake of the B. lactis V9 probiotic. Therefore, effective host gut colonization of the probiotic was crucial for its ability to function as a probiotic. Finally, we propose a potential mechanism by which B. lactis V9 regulates the levels of sex hormones by manipulating the intestinal microbiome in PCOS patients.

Design of Primers for Evaluation of Lactic Acid Bacteria Populations in Complex Biological Samples.

Lactic acid bacteria (LAB) are important for human health. However, the relative abundance of LAB in complex samples, such as fecal samples, is low and their presence and diversity (at the species level) is understudied. Therefore, we designed LAB-specific primer pairs based on 16S rRNA gene consensus sequences from 443 species of LAB from seven genera. The LAB strains selected were genetically similar and known to play a role in human health. Prior to primer design, we obtained consistent sequences for the primer-binding sites by comparing the 16S rRNA gene sequences, manually identifying single-stranded primers and modifying these primers using degenerate bases. We assembled primer pairs with product sizes of >400 bp. Optimal LAB-specific primers were screened using three methods: PCR amplification, agarose gel electrophoresis and single-molecule real-time (SMRT) sequencing analysis. During the SMRT analysis procedure, we focused on sequence reads and diversity at the species level of target LAB in three fecal samples, using the universal bacterium primer 27f/1492r as a reference control. We created a phylogenetic tree to confirm the ability of the best candidate primer pair to differentiate amongst species. The results revealed that LAB-specific primer L5, with a product size of 750 bp, could generate 3222, 2552, and 3405 sequence reads from fecal Samples 1, 2, and 3. This represented 14, 13 and 10% of all target LAB sequence reads, respectively, compared with 2, 0.8, and 0.8% using the 27f/1492r primer. In addition, L5 detected LAB that were in low abundance and could not be detected using the 27f/1492r primer. The phylogenetic tree based on the alignments between the forward and reverse primer of L5 showed that species within the seven target LAB genera could be distinguished from each other, confirming L5 is a powerful tool for inferring phylogenetic relationships amongst LAB species. In conclusion, L5 is a LAB-specific primer that can be used for high-throughput sequencing and identification of taxa to the species level, especially in complex samples with relatively low LAB content. This enables further research on LAB population diversity in complex ecosystem, and on relationships between LAB and their hosts.