Identification, Screening and Antibacterial Mechanism Analysis of Novel Antimicrobial Peptides from Sturgeon (Acipenser ruthenus) Spermary.

Fish is an important source of antimicrobial peptides. This study aimed to identify and screen antibacterial peptides with excellent antibacterial activity derived from sturgeon spermary peptides (SSPs) and to analyze their antibacterial activity and mechanism. Liquid chromatography-mass spectrometry/mass spectrometry methods were used to analyze and identify peptide sequences, computational prediction tool and molecular docking methods were used for virtual screening of antimicrobial peptides, and finally, candidate peptides were synthesized by solid-phase synthesis method. The results demonstrate that SSPs have excellent inhibitory activity against Escherichia coli with an inhibitory rate of 76.46%. Most parts of the SSPs were derived from the sturgeon (Acipenser ruthenus) histones, and the coverage of histone H2B was the highest (45%). Two novel peptides (NDEELNKLM and RSSKRRQ) were obtained by in silico prediction tools and molecular docking, which may interact with the DNA gyrase and dihydrofolate reductase of E. coli by forming salt bridges and hydrogen bonds. Compared to the individual peptides, the antibacterial effect was significantly improved by mixing the two peptides in equal proportions. Two novel peptides change the permeability of the E. coli cell membranes and may exert antimicrobial activity by inhibiting the metabolic process of the nucleic acids.

Comparative proteomics analysis of spermary and ovary in Hyriopsis schlegelii.

We provide the first large-scale quantitative proteomics analysis in Hyriopsis schlegelii. To investigate the proteins expressed in the gonads, a quantitative proteomics approach has been utilized to analyze differentially expressed proteins between the spermary and ovary. In this study, we identified and quantified 2416 proteins in the gonads of Hyriopsis schlegelii. Of these, 559 proteins showed significantly different expression between the spermary and ovary. Some specific proteins expressed in either the spermary or ovary were identified in Hyriopsis schlegelii. In addition, a series of proteins related to gametogenesis were also identified. Compared with previous reports, many proteins in Hyriopsis schlegelii identified here have different expression patterns between the spermary and ovary. The special hermaphroditism in Hyriopsis schlegelii may contribute to these inconsistent results. The provided proteomics data could be considered as a starting point for subsequent studies focusing on the proteins involved in sexual gland development and maturity.

De novo transcriptome sequencing to identify the sex-determination genes in Hyriopsis schlegelii.

This study presents the first analysis of expressed transcripts in the spermary and ovary of Hyriopsis schlegelii (H. schlegelii). A total of 132,055 unigenes were obtained and 31,781 of these genes were annotated. In addition, 19,511 upregulated and 25,911 downregulated unigenes were identified in the spermary. Ten sex-determination genes were selected and further analyzed by real-time PCR. In addition, mammalian genes reported to govern sex-determination pathways, including Sry, Dmrt1, Dmrt2, Sox9, GATA4, and WT1 in males and Wnt4, Rspo1, Foxl2, and ß-catenin in females, were also identified in H. schlegelii. These results suggest that H. schlegelii and mammals use similar gene regulatory mechanisms to control sex determination. Moreover, genes associated with dosage compensation mechanisms, such as Msl1, Msl2, and Msl3, and hermaphrodite phenotypes, such as Tra-1, Tra-2α, Tra-2ß, Fem1A, Fem1B, and Fem1C, were also identified in H. schlegelii. The identification of these genes indicates that diverse regulatory mechanisms regulate sexual polymorphism in H. schlegelii.

Antimicrobial activities and mechanism of sturgeon spermary protein extracts against Escherichia coli.

This study aimed to evaluate the antimicrobial activities and mechanism of sturgeon spermary protein extracts (SSPE) against Escherichia coli. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined. Cell structural change was analyzed using scanning electron microscopy-energy dispersive X-ray spectrometry and transmission electron microscope. Moreover, pH, zeta potential, membrane potential, intracellular ATP concentrations and the interaction of SSPE with genomic DNA were analyzed. Results showed that molecular weight of SSPE is 13.4 kDa, the content of basic amino acids is the highest, in which arginine accounts for 73.2%. The MIC and MBC of SSPE for E. coli were 0.05 and 5 mg/mL, respectively. After SSPE treatment, cell membrane permeability changes, zeta potential decrease and genomic DNA lysis occurred in E. coli, which indicated it exerted bacteriostatic effects either independently or simultaneously by destroying the cell membrane and genomic DNA. These findings indicated that SSPE has potential to be a natural antiseptic.