Rixin Wang

Marine fauna provides a plentiful repository of peptides and bioactive proteins. Peptides and proteins isolated from marine animals have been studied and applied in the development of food supplements, drugs, and cosmeceutical products because of their special bioactivities, such as anti-inflammatory and antioxidant effects This study focused on exploring the alleviating effects of five major marine animal-derived peptides (Apostichopus japonicus, Acaudina leucoprocta, Melanogrammus aeglefinus, Phascolosoma esculenta and Rhopilema esculentum) on adjuvant-induced arthritis (AIA). The treatment with five marine animals-derived peptides downregulated the expression levels of pro-inflammatory cytokines of IL-1β, IL-17 and TNF-α in the bones of the mice with AIA and alleviated the rough surface of bone tissues significantly. A. japonicus-treatment ameliorates inflammation by restoring NF-κB pathway in AIA mice. High-throughput sequencing of the gut microbiota based on 16S rRNA sequencing revealed that A. japonicus peptide-treated AIA mice showed alterations and imbalance of intestinal flora and an increased abundance of Lactobacillus and Clostridium. Furthermore, metabolomic analysis showed that the level of SCFAs in the feces was enhanced to different degrees in mice treated with five major marine animal-derived peptides. Taken together, we propose that major marine animal-derived peptides can alleviate arthritis by improving the imbalance in the gut flora and increasing SCFA production to varying degrees.

Fructose consumption has risen dramatically in recent decades due to the use of sucrose and high fructose corn syrup in beverages and processed foods, contributing to rising rates of hyperuricemia. The purpose of this experiment was to explore the anti-hyperuricemia effects of an active oligopeptide (GPSGRP) derived from sea cucumber in fructose induced hyperuricemia mouse model, and to clarify the underlying mechanism in sight of gut microbiota and serum metabolites. Peptide GPSGRP treatment rebalanced uric acid metabolism and alleviated inflammatory response in mice. In addition, treatment with GPSGRP decreased the abundance of Bacteroides and Proteobacteria at the phylum level, Muribaculum, Prevotella and Bacteroides at the genus level, and inhibited the related pathways of purine metabolism and glycolysis/gluconeogenesis metabolism. Moreover, serum metabolites, including linoleic acid, indole and its derivatives, arachidonic acid and uridine, as well as related metabolic pathways, such as tricarboxylic acid cycle, ketone production and sugar production, were altered in response to GPSGRP treatment. This study provides a valuable reference for the application and development of marine biological peptides in uric acid management.

Limosilactobacillus reuteri is an indigenous inhabitant of the animal gut known for its probiotic effects on the host. In our previous study, a large number of L. reuteri strains were isolated from the gastrointestinal tract of mice recovering from ulcerative colitis, from which we randomly selected L. reuteri RE225 for whole genome sequencing to explore its probiotic properties. The results of next-generation sequencing and third-generation single molecule sequencing showed that L. reuteri RE225 contained many genes encoding functional proteins associated with adhesion, anti-inflammatory and pathogen inhibition. And compared to other L. reuteri strains in NCBI, L. reuteri RE225 has unique gene families with probiotic functions. In order to further explore the probiotic effect of the L. reuteri RE225, the derived peptides were identified by LC-MS/MS, and the peptides with tumor necrosis factor-α binding ability were screened by reverse molecular docking and microscale thermophoresis. Finally, cell experiments demonstrated the anti-inflammatory ability of the peptides. Western blotting and qPCR analyses confirmed that the selected peptides might alleviate LPS-induced inflammation in NCM460 cells by inhibiting JAK2/STAT3 pathway activation.

A new strain of Bacillus velezensis NDB was isolated from Xiangshan Harbor and antibacterial test revealed antibacterial activity of this strain against 12 major pathogenic bacteria. The whole genome of the bacterium was sequenced and found to consist of a 4,214,838 bp circular chromosome and a 7410 bp circular plasmid. Furthermore, it was predicted by AntiSMASH and BAGEL4 to have 12 clusters of secondary metabolism genes for the synthesis of the inhibitors, fengycin, bacillomycin, macrolactin H, bacillaene, and difficidin, and there were also five clusters encoding potentially novel antimicrobial substances, as well as three bacteriocin biosynthesis gene clusters of amylocyclicin, ComX1, and LCI. qRT-PCR revealed significant up-regulation of antimicrobial secondary metabolite synthesis genes after 24 h of antagonism with pathogenic bacteria. Furthermore, MALDI-TOF mass spectrometry revealed that it can secrete surfactin non-ribosomal peptide synthase and polyketide synthase to exert antibacterial effects. GC-MS was used to analyze methanol extract of B. velezensis NDB, a total of 68 compounds were identified and these metabolites include 16 amino acids, 17 acids, 3 amines, 11 sugars, 11 alcohols, 1 ester, and 9 other compounds which can inhibit pathogenic bacteria by initiating the antibiotic secretion pathway. A comparative genomic analysis of gene families showed that the specificity of B. velezensis NDB was mainly reflected in environmental adaptability. Overall, this research on B. velezensis NDB provides the basis for elucidating its biocontrol effect and promotes its future application as a probiotic.

Background: Generally, enterococci bacteria cause nosocomial infections and are major indicators of bacterial contamination in marine bathing beach. However, a method for the rapid and simultaneous detection of multiple pathogenic enterococci has not been developed on account of the wide variety of pathogenic enterococci and their existence in complex matrices.Methods: Immunoinformatics tools were used to design a multi-epitope antigen for the detection of various pathogenic enterococci by using the sequence of dltD gene on enterococci lipoteichoic acid (LTA) surface, which is associated with toxicological effects. The multi-epitopes included enterococci such as Enterococcus faecalis, E. gallinarum, E. raffinosus, E. durans, E. faecium, E. hirae, E. thailandicus, E. casseliflavus, E. avium, E. mundtii, E. lactis, E. solitarius, E. pseudoavium, and E. malodoratum. Microscale thermophoresis (MST) and western blot were carried out to detect the affinity between multi-epitope antigens and antibodies and between multi-epitope antibodies and bacteria. Furthermore, the detection of pathogenic enterococci was carried out by using immunomagnetic beads (IMBs) and immune chromatographic test strip (ICTS).Results: The multi-epitope antibody had a satisfactory affinity to the antigen and enterococci. IMBs and ICTS were detected with a minimum of 101 CFU/mL and showed incompatibility for Vibrio parahemolyticus, V. vulnifcus, V. harveyi, V. anguillarum, and Edwardsiella tarda.Implication: The present study demonstrated that the multi-epitope antigens exhibited excellent specificity and sensitivity, making them highly suitable for efficient on-site screening of enterococci bacteria in marine bathing beaches.

Many studies have focused on the influence of dietary supplements on gut microbiota composition, but limited research have reported their effects on specific bacterial species in the gut. Lactiplantibacillus plantarum is one of the most widely studied probiotics, with a wide range of sources and good environmental adaptability. In this study, in order to elucidate the adaptation strategies of L. plantarum to the gut of mice supplemented with carbohydrates, peptides and minerals, whole genome resequencing and intracellular metabolites detection were performed, and high-frequency mutant genes and differential metabolites were screened. The results suggested different types of dietary supplements do have different effects on L. plantarum from the gut of mice. Additionally, KEGG annotation unveiled that the effects of these dietary supplements on the gene level of L. plantarum primarily pertained to environmental information processing, while the differential metabolites were predominantly associated with metabolism. This study provided new perspectives on the adaptive mechanism of L. plantarum in response to the host’s gut environment, suggesting that the diversity of the genome and metabolome of L. plantarum was correlated with dietary supplements. Furthermore, this study offered useful guidance in the effective utilization of dietary supplements.

Ultraviolet B (UVB)-induced cell death causes skin photoaging. In this study, we investigated the protective effect of Melanogrammus aeglefinus skin oligopeptide (MSOP) in UVB-irradiated human keratinocytes. The method of preparing MSOP was optimized, and three peptides with high abundance, VADML (Val-Ala-Asp-Met-Leu), IARF (Ile-Ala-Arg-Phe) and SSPSF (Ser-Ser-Pro-Ser-Phe), were identified. Discovery Studio predicted that these peptides interacted with Keap1 and contributed to antioxidant activity. Therefore, a UVB-induced cell model was used to explore the beneficial effects of MSOP in vitro. The activities of superoxide dismutase and glutathione peroxidase were increased in the MSOP-treated groups, while the malondialdehyde content was decreased. In addition, 23 differentially expressed proteins were identified through quantitative proteomics analysis; among them, the upregulation of Nrf2 and downregulation of Keap1, which are involved in the Keap1/Nrf2/ARE signaling pathway, contributed to the antioxidant process. Based on this study, MSOP might be an alternative agent for protecting the skin against UVB exposure.

Archaea play a significant role in regulating the biogeochemical processes of marine ecosystems. In this study, the high-throughput sequencing was used to explore the archaeal communities in the seawater from the hypoxic and non-hypoxic zones of the Changjiang Estuary. Thaumarchaeota dominated the archaeal communities in the hypoxic zones (bottom water), and Euryarchaeota were mainly distributed in the non-hypoxic zones (surface water). However, the diversity and richness of the archaeal communities showed no obvious difference in the hypoxic and non-hypoxic zones. Moreover, Thaumarchaeota and Nitrosopumilales were positively correlated with salinity, but negatively correlated with dissolved oxygen (DO) and temperature. Temperature, phosphorus, and dissolved oxygen had significant correlations with archaeal richness, while ammonia nitrogen was correlated with archaeal diversity. The networks of archaeal communities possessed a high proportion of positive interspecific interaction and revealed that the Marine Group II species may play distinct roles in both hypoxic and non-hypoxic zones. The current work assessed the influence of dissolved oxygen on the archaeal community patterns and network interaction, thereby illumining the community structure shift of archaea caused by the hypoxia phenomenon in the Changjiang Estuary, which laid a foundation for the future studies on the ecological functions of archaea in estuary ecosystems.

Staphylococcus aureus (S. aureus) has a strong tolerance to high salt stress. It is a major reason as to why the contamination of S. aureus in salted food cannot be eradicated. To elucidate its response and survival mechanisms, changes in the morphology, biofilm formation, virulence, transcriptome, and metabolome of S. aureus were investigated. IsaA positively regulates and participates in the formation of biofilm. Virulence was downregulated to reduce the depletion of nonessential cellular functions. Inositol phosphate metabolism was downregulated to reduce the conversion of functional molecules. The MtsABC transport system was downregulated to reduce ion transport and signaling. Aminoacyl-tRNA biosynthesis was upregulated to improve cellular homeostasis. The betaine biosynthesis pathway was upregulated to protect the active structure of proteins and nucleic acids. Within a 10% NaCl concentration, the L-proline content was upregulated to increase osmotic stability. In addition, 20 hub genes were identified through an interaction analysis. The findings provide theoretical support for the prevention and control of salt-tolerant bacteria in salted foods.

Staphylococcus aureus possesses an extraordinary ability to deal with a wide range of osmotic pressure. This study performed transcriptomic and metabolomic analyses on the potential mechanism of gradient salinity stress adaptation in S. aureus ZS01. The results revealed that CPS biosynthetic protein genes were candidate target genes for directly regulating the phenotypic changes of biofilm. Inositol phosphate metabolism was downregulated to reduce the conversion of functional molecules. The gluconeogenesis pathway and histidine synthesis were downregulated to reduce the production of endogenous glucose. The pyruvate metabolism pathway was upregulated to promote the accumulation of succinate. TCA cycle metabolism pathway was downregulated to reduce unnecessary energy loss. l-Proline was accumulated to regulate osmotic pressure. Therefore, these self-protection mechanisms can protect cells from hypertonic environments and help them focus on survival. In addition, we identified ten hub genes. The findings will aid in the prevention and treatment strategies of S. aureus infections.