Objective To establish an immature rabbit model of avascular necrosis of the femoral head in-duced by exercise. Methods Ten male, immature New Zealand white rabbits were subjected to large range, in- tense passive movement and concentric impingement on their right hips for 4 weeks. The left hips were used as self-controls. Then X-ray and magnetic resonance imaging, gross anatomical observation and histological examination were used to evaluate avascular necrosis of the femoral head. Result After 4 weeks, avascular necrosis of the femoral head was successfully replicated. Increased bone density, decreased osteoepiphysis height and indistinct bone trabec-ula were found in X-rays of the right hips. In MRI images obvious joint hydrops could be detected in all right hips, and schistic low signal areas in the femoral head could be seen in TIWI and T2WI images. Thin bone trabeculae of low density, with irregular and broken structures, were also found in H-E sections. Conclusion An immature rab-bit model of avascular necrosis of femoral head can be successfully induced through large range, intense, passive movement and concentric impingement.

Objective:To study the molecular phylogeny and virulence gene profile of Francisella salimarina. Methods:Phylogenetic analysis of Francisella salimarina was performed based on the global genome data of related Francisella species on GenBank database. The consistency in phylogenetic analysis based on single marker genes (such as 16S rRNA gene, rpoB gene and mdh gene) and the core genome as compared. Virulence genes and antibiotic resistance genes were annotated using the virulence factor database (VFDB) and the Comprehensive Antibiotic Resistance Database (CARD), respectively. The virulence of Francisella salimarina was analyzed with a Galleria mellonella (greater wax moth) infection model using Francisella philomiragia ATCC 25015 T as reference strain. Results:The phylogenetic analysis revealed that Francisella salimarina was closely related to Francisella philomiragia. The phylogenetic tree based on mdh gene was highly similar to that based on the core genome. Francisella salimarina could be differentiated from other related species by 16S rRNA gene or mdh gene, with the latter being more accurate. Eight Francisella salimarina strains carried multiple virulence genes, mainly involved in secretion, adhesion, immune regulation, motility and stress survival. Moreover, beta-lactam resistance gene blaFPH was identified in all eight strains. Francisella salimarina showed high lethality in the Galleria mellonella infection model, which was similar to Francisella philomiragia ATCC 25015 T. Conclusions:Francisella salimarina was a rare pathogen with similar pathogenicity to Francisella philomiragia. The mdh gene could be used as a molecular target for rapid identification of Francisella salimarina.

Depsides and depsidones have attracted attention for biosynthetic studies due to their broad biological activities and structural diversity. Previous structure‒activity relationships indicated that triple halogenated depsidones display the best anti-pathogenic activity. However, the gene cluster and the tailoring steps responsible for halogenated depsidone nornidulin ( 3) remain enigmatic. In this study, we disclosed the complete biosynthetic pathway of the halogenated depsidone through in vivo gene disruption, heterologous expression and in vitro biochemical experiments. We demonstrated an unusual depside skeleton biosynthesis process mediated by both highly-reducing polyketide synthase and non-reducing polyketide synthase, which is distinct from the common depside skeleton biosynthesis. This skeleton was subsequently modified by two in-cluster enzymes DepG and DepF for the ether bond formation and decarboxylation, respectively. In addition, the decarboxylase DepF exhibited substrate promiscuity for different scaffold substrates. Finally, and interestingly, we discovered a halogenase encoded remotely from the biosynthetic gene cluster, which catalyzes triple-halogenation to produce the active end product nornidulin ( 3). These discoveries provide new insights for further understanding the biosynthesis of depsidones and their derivatives.