Antimicrobial resistance has emerged as a serious threat to public health. Bacterial biofilm, as a natural lifestyle, is a major contributor to resistance to antimicrobials. Azalomycin F_5a, a natural guanidine-containing polyhydroxy macrolide, has remarkable activities against Gram-positive bacteria, including Staphylococcus aureus, a major causative agent of hospital-acquired infections. To further evaluate its potential to be developed as a new antimicrobial agent, its influence on S. aureus biofilm formation was evaluated using the crystal violet method, and then its eradication effect against mature biofilms was determined by confocal laser scanning microscopy, the drop plate method, and regrowth experiments. The results showed that azalomycin F_5a could significantly inhibit S. aureus biofilm formation, and such effects were concentration dependent. In addition, it can also eradicate S. aureus mature biofilms with the minimum biofilm eradication concentration of 32.0 μg/mL. As extracellular deoxyribonucleic acid (eDNA) plays important roles in the structural integrity of bacterial biofilm, its influence on the eDNA release in S. aureus biofilm was further analyzed using gel electrophoresis. Combined with our previous works, these results indicate that azalomycin F_5a could rapidly penetrate biofilm and causes damages to the cell membrane, leading to an increase in DNase release and eventually eradicating S. aureus biofilm.

Background: The swamp eel (Monopterus albus) is a commercially important farmed species in China. The dysbiosis and homeostasis of gut microbiota has been suggested to be associated with the swamp eel’s disease pathogenesis and food digestion. Although the contributions of gut microbiome in fish growth and health has been increasingly recognized, little is known about the microbial community in the intestine of the swamp eel (Monopterus albus). Methods: The intestinal microbiomes of the five distinct gut sections (midgut content and mucosa, hindgut content and mucosa, and stools) of swamp eel were compared using Illumina MiSeq sequencing of the bacterial 16S rRNA gene sequence and statistical analysis. Results: The results showed that the number of observed OTUs in the intestine decreased proximally to distally. Principal coordinate analysis revealed significant separations among samples from different gut sections. There were 54 core OTUs shared by all gut sections and 36 of these core OTUs varied significantly in their abundances. Additionally, we discovered 66 section-specific enriched KEGG pathways. These section-specific enriched microbial taxa (e.g., Bacillus, Lactobacillus) and potential function capacities (e.g., amino acid metabolism, carbohydrate metabolism) might play vital roles in nutrient metabolism, immune modulation and host-microbe interactions of the swamp eel. Conclusions: Our results showed that microbial diversity, composition and function capacity varied substantially across different gut sections. The gut section-specific enriched core microbial taxa and function capacities may perform important roles in swamp eel’s nutrient metabolism, immune modulation, and host-microbe interactions. This study should provide insights into the gut microbiome of the swamp eel.

Monopterus albus is a special economic aquatic animal in China. Most of cultured M. albus are wild species captured from different areas, and this makes the wild resources of M. albus are under great threat. Microsatellite markers can help us understand the genetic resources of M. albus in different areas. In this study, using RAD-seq (restriction site associated DNA sequencing) protocol, a total of 9,897 microsatellites were identified in the genome with average frequency of 195 microsatellites per megabase of genomic sequences. Among these SSRs, the dinucleotide repeat motif was the most abundant type representing 61.77 % of the total microsatellite loci, followed by pentanucleotides (13.91 %), trinucleotides (12.08 %), tetranucleotides (9.30 %) and hexanucleotides (2.94 %). A total of 100 SSR primers were designed for PCR amplification. The polymorphism analysis showed that 28 primer pairs could successfully amplify the polymorphic fragments and the number of alleles per polymorphic locus ranged from 2 to 13, with an average of 5.70 alleles/locus. The values of observed and expected heterozygosity’s ranged from 0.0333 to 0.8000 and 0.0333 to 0.8887, respectively. This microsatellite locus will be useful to understand the structure, genetic diversity, and genetic difference of this species.

Strain ZZ035 was isolated from a folk medicinal soil in China. Polyphasic taxonomy procedure indicated that this strain belonged to the genus Streptomyces and was closest to S. cinnamonensis with high similarities (99.2%) of 16S rDNA sequence. 1 was isolated from the broth of this strain and identified as 5-amonimethyl-2-iminoimidazolidine-4-carboxylic acid. Its chemical structure was established by its spectroscopic data, and 1H and 13C signals were assigned by its 1H, 13C, Dept and HSQC spectra. Considering that 1 was a γ-aminobutric acid (GABA) derivative, its inhibitory activity against GABA-aminotransferase (GABA-AT) was assayed, and the result showed that 1 can inhibit GABA-AT activity with the 50% inhibitory concentration of approximately 60 μM. As 1 was a 2,3-disubstituted GABA derivative not published before, the approximate GABA-AT inhibitory activity of 1 compared to positive control vigabatrin showed that 1 were worthy of further research and developing.