De novo transcriptome analysis and antimicrobial peptides screening in skin of Paa boulengeri

De Novo Transcriptomic Characterization Enables Novel Microsatellite Identification and Marker Development in Betta splendens

The wild populations of the commercially valuable ornamental fish species, Betta splendens, and its germplasm resources have long been threatened by habitat degradation and contamination with artificially bred fish. Because of the lack of effective marker resources, population genetics research projects are severely hampered. To generate genetic data for developing polymorphic simple sequence repeat (SSR) markers and identifying functional genes, transcriptomic analysis was performed. Illumina paired-end sequencing yielded 105,505,486 clean reads, which were then de novo assembled into 69,836 unigenes. Of these, 35,751 were annotated in the non-redundant, EuKaryotic Orthologous Group, Swiss-Prot, Kyoto Encyclopedia of Genes and Genomes and Gene Ontology databases. A total of 12,751 SSR loci were identified from the transcripts and 7970 primer pairs were designed. One hundred primer pairs were randomly selected for PCR validation and 53 successfully generated target amplification products. Further validation demonstrated that 36% (n = 19) of the 53 amplified loci were polymorphic. These data could not only enrich the genetic information for the identification of functional genes but also effectively facilitate the development of SSR markers. Such knowledge would accelerate further studies on the genetic variation and evolution, comparative genomics, linkage mapping and molecular breeding in B. splendens.

Antibacterial effects of a polypeptide-enriched extract of Rana chensinensis via the regulation of energy metabolism

The improper usage of antibiotics is known to cause widespread antibiotic resistance. In this study, the antibacterial effects of a polypeptide-enriched extract from the skin of the amphibian Rana chensinensis (RCP) were evaluated against the Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa, the Gram-positive bacterium Staphylococcus aureus and the fungus Candida albicans. The mechanisms underlying these effects were also studied, and the minimum inhibitory concentration of RCP was determined for each species. Analyses of the levels of adenosine triphosphates (ATPases), including Na⁺/K⁺-ATPase and Ca²⁺-ATPase, and scanning electron microscopy confirmed that RCP damaged the microbial cell walls and membranes. RCP perturbed microbial metabolism and particularly affected the tricarboxylic acid cycle (TCA), suggesting that this agent downregulated the levels of succinate dehydrogenase, malate dehydrogenase and ATPase activity in cells. Furthermore, RCP caused the leakage of genetic material from all four microbial strains. In conclusion, RCP effectively inhibited the growth of Gram-negative and Gram-positive bacteria and a fungal species by disrupting energy metabolic processes.