Generation, Maintenance, and Identification of Germ-Free Zebrafish Models from Larvae to Juvenile Stages.

Zebrafish serve as valuable models for research on growth, immunity, and gut microbiota due to their genomic similarities with mammals, transparent embryos developed in a relatively clean chorion environment, and extremely rapid development of larvae compared to rodent models. Germ-free (GF) zebrafish (Danio rerio) are crucial for evaluating pollutant toxicity and establishing human-like disease models related to microbial functions. In comparison to conventionally raised (CR) models (fish in common husbandry), GF zebrafish allow for more accurate manipulation of the host microbiota, aiding in determining the causal relationship between microorganisms and hosts. Consequently, they play a critical role in advancing our understanding of these relationships. However, GF zebrafish models are typically generated and researched during the early life stages (from embryos to larvae) due to limitations in immune function and nutrient absorption. This study optimizes the generation, maintenance, and identification of early GF zebrafish models without feeding and with long-term feeding using GF food (such as Artemia sp., brine shrimp). Throughout the process, daily sampling and culture were performed and identified through multiple detections, including plates and 16S rRNA sequencing. The aseptic rate, survival, and developmental indexes of GF zebrafish were recorded to ensure the quality and quantity of the generated models. Importantly, this study provides details on bacterial isolation and infection techniques for GF fish, enabling the efficient creation of GF fish models from larvae to juvenile stages with GF food support. By applying these procedures in biomedical research, scientists can better understand the relationships between intestinal bacterial functions and host health.

Prodigiosin as an antibiofilm agent against multidrug-resistant Staphylococcus aureus.

Staphylococcus aureus is known for forming bacterial biofilms that confer increased antimicrobial resistance. Combining antibiotics with antibiofilm agents is an alternative approach, but the antibiofilm ability of prodigiosin (PG), a potential antibiotic synergist, against antimicrobial-resistant (AMR) S. aureus remains to be understood. The antibiofilm activity of PG against 29 clinical AMR S. aureus strains was evaluated using crystal violet staining, and its synergistic effects with vancomycin (VAN) was confirmed using the checkerboard test. The viability and metabolic activity of biofilms and planktonic cells were also assessed. The results revealed that PG exhibited promising inhibitory activity against biofilm formation and synergistic activity with VAN. It effectively reduced the metabolic activity of biofilms and suppressed the production of exopolysaccharides, which might be attributed to the downregulation of biofilm-related genes such as sarA, agrA, and icaA. These findings suggest that PG could be used as a preventive coating or adjuvant against biofilms in clinical settings.

Prodigiosin derived from chromium-resistant Serratia sp. prevents inflammation and modulates gut microbiota homeostasis in DSS-induced colitis mice.

Prodigiosin (PG) is a secondary metabolite of microorganisms with anticancer, antimalarial, antibacterial and immunomodulatory effects. However, the modulatory effects on gut microbiome and intestinal immune microenvironment have never been explored in the ulcerative colitis (UC) mice model. In this study, 2.5% dextran sulfate sodium (DSS) induced UC mice model was constructed to investigate the effects of PG derived from a chromium-resistant Serratia sp. on the intestinal flora and inflammatory response. The results showed that prodigiosin administration attenuated the DSS-induced UC symptoms, including preventing the reduction of colonic length and DSS-induced mortality. Furthermore, prodigiosin ameliorated the DSS-induced gut microbiota community dysbiosis by restoring the abundance of Bacteroidota. At the genus level, the declined abundance of Bifidobacterium, Allobaculum and Akkermannia in UC mice was elevated by the treatment of PG. Pathological results by H&E staining showed that PG prevented the appearance of distortion and atrophy of crypt and neutrophil infiltration in a dose-dependent manner. RT-PCR revealed that the expression levels of the inflammatory factors IL-1ß, IL-6 and IL-10 were significantly suppressed, and the expression of the intestinal tight junction protein Claudin-1, Occludin and ZO-1 were upregulted in PG-treated UC mice. Conclusively, our results revealed that prodigiosin effectively prevented inflammatory response and protected intestinal barrier integrity of DSS-induced colitis mice via modulating gut microbiota community structure, suppressing inflammatory factors' expression, and accelerating the expression of intestinal tight junction protein. These results will provide new insights into the interaction of prodigiosin with intestinal microbiota homeostasis and its application in clinical against inflammatory bowel disease.

Modulatory Effects of Huoxiang Zhengqi Oral Liquid on Gut Microbiome Homeostasis Based on Healthy Adults and Antibiotic-Induced Gut Microbial Dysbiosis Mice Model.

Traditional herbal medicine (THM) is used worldwide for its safety and effectiveness against various diseases. Huoxiang Zhengqi (HXZQ) is an extensively used Chinese THM formula targeting gastrointestinal disordered gastroenteritis via regulating the intestinal microbiome/immuno-microenvironment. However, the specific mechanisms remain largely unexplored, besides as a lifestyle drug, its safety on the gut microbiome homeostasis has never been investigated. In this study, the effects of HXZQ on the gut microbiome of healthy adults were investigated for the first time, and the antibiotic-induced gut microbiota dysbiosis mice model was applied for verification. Based on healthy adults, our results revealed that HXZQ exhibited mild and positive impacts on the bacterial diversity and the composition of the gut microbiome in a healthy state. As for an unhealthy state of the gut microbiome (with low bacterial diversity and deficient compositions), HXZQ significantly restored the bacterial diversity and recovered the abundance of Bacteroidetes. In the antibiotic-induced mice model, HXZQ distinctly revived the deficient gut microbial compositions impaired by antibiotics. At the genus level, the abundances that responded most strongly and positively to HXZQ were Bifidobacterium in healthy adults and Muribaculaceae, Lactobacillus, and Akkermansia in mice. In contrast, the abundance of Blautia in healthy adults, Enterococcus, and Klebsiella in mice showed inversely associated with HXZQ administration. At last, HXZQ might exhibit an anti-inflammatory effect by regulating the concentration of interleukin-6 in plasma while causing no significant changes in the colon tissue structure in mice. In conclusion, our results elucidate that the safety of HXZQ in daily use further reveals the modulatory effects of HXZQ on gut microbial community structure. These results will provide new insights into the interaction of THM and gut microbiome homeostasis and clues about the safe use of THM as a lifestyle drug for its further development.

Molecular structure and vibrational spectra of three substituted 4-thioflavones by density functional theory and ab initio Hartree-Fock calculations.

The vibrational frequencies of three substituted 4-thioflavones in the ground state have been calculated using the Hartree-Fock and density functional method (B3LYP) with 6-31G* and 6-31+G** basis sets. The structural analysis shows that there exists H-bonding in the selected compounds and the hydrogen bond lengths increase with the augment of the conjugate parameters of the substituent group on the benzene ring. A complete vibrational assignment aided by the theoretical harmonic wavenumber analysis was proposed. The theoretical spectrograms for FT-IR spectra of the title compounds have been constructed. In addition, it is noted that the selected compounds show significant activity against Shigella flexniri. Several electronic properties and thermodynamic parameters were also calculated.