Impact of Bacillus licheniformis from yaks following antibiotic therapy in mouse model

Gut microorganism (GM) is an integral component of the host microbiome and health system. Abuse of antibiotics disrupts the equilibrium of the microbiome, affecting environmental pathogens and host-associated bacteria alike. However, relatively little research on Bacillus licheniformis alleviates the adverse effects of antibiotics. To test the effect of B. licheniformis as a probiotic supplement against the effects of antibiotics, cefalexin was applied, and the recovery from cefalexin-induced jejunal community disorder and intestinal barrier damage was investigated by pathology, real-time PCR (RT-PCR), and high-throughput sequencing (HTS). The result showed that A group (antibiotic treatment) significantly reduced body weight and decreased the length of jejunal intestinal villi and the villi to crypt (V/C) value, which also caused structural damage to the jejunal mucosa. Meanwhile, antibiotic treatment suppressed the mRNA expression of tight junction proteins ZO-1, claudin, occludin, and Ki67 and elevated MUC2 expression more than the other Groups (P < 0.05 and P < 0.01). However, T group (B. licheniformis supplements after antibiotic treatment) restored the expression of the above genes, and there was no statistically significant difference compared to the control group (P > 0.05). Moreover, the antibiotic treatment increased the relative abundance of 4 bacterial phyla affiliated with 16 bacterial genera in the jejunum community, including the dominant Firmicutes, Proteobacteria, and Cyanobacteria in the jejunum. B. licheniformis supplements after antibiotic treatment reduced the relative abundance of Bacteroidetes and Proteobacteria and increased the relative abundance of Firmicutes, Epsilonbacteraeota, Lactobacillus, and Candidatus Stoquefichus. This study uses mimic real-world exposure scenarios by considering the concentration and duration of exposure relevant to environmental antibiotic contamination levels. We described the post-antibiotic treatment with B. licheniformis could restore intestinal microbiome disorders and repair the intestinal barrier. KEY POINTS: • B. licheniformis post-antibiotics restore gut balance, repair barrier, and aid health • Antibiotics harm the gut barrier, alter structure, and raise disease risk • Long-term antibiotics affect the gut and increase disease susceptibility.

Probiotic Potential of Bacillus amyloliquefaciens Isolated from Tibetan Yaks

The Tibetan livestock sector is now ailing from many infectious ailments brought on by harmful microorganisms. Therefore, this research aimed to assess the probiotic potential and safety of Bacillus amyloliquefaciens isolated from yaks in the Tibet area to provide upper-edge strain resources for probiotics development. The four strains isolated from the intestine of yaks had been identified as Bacillus amyloliquefaciens after the 16S rRNA sequence. The ethanol, bile salt, and acid tolerance revealed that the isolates had significant tolerance levels. The antibiotics susceptibility assay showed that the strains were sensitive to commonly used antibiotics, while the antibacterial assay prevented the isolates from outperforming five harmful bacteria in terms of antibacterial potency. Moreover, it was evident that strain BA5 had the strongest activity to scavenge hydroxyl radical and reduce power. According to the animal experiment, no apparent pathological change was observed in intestinal tissue sections. Furthermore, the strain had a positive effect on promoting the development of jejunal villi referred to its safety. Therefore, more research is required into the bacteriostatic and antioxidant capabilities of isolates in animal production.