Phytoplankton are key primary producers in marine ecosystems, and their community composition is influenced not only by environmental factors but also by biological factors such as parasitic organisms. However, the relationships between parasitic eukaryotes and phytoplankton in coastal bays remain poorly understood. Objective To investigate the community composition, seasonal succession, and interactions of dominant phytoplankton, including diatoms, dinoflagellates, and their parasitic eukaryotes, Syndiniales, in Sanmen Bay, Zhejiang Province during summer and autumn. Methods Surface water samples were collected from Sanmen Bay in September (summer) and November (autumn) 2019. High-throughput sequencing was performed for the V4 region of the 18S rRNA gene of eukaryotic microbes. Principal coordinate analysis, co-occurrence network analysis, and bipartite network analysis were employed to explore the succession and interactions of diatom, dinoflagellate, and Syndiniales communities. Results Diatom communities exhibited pronounced seasonal variations, with the relative abundance of 36.9% in summer and 5.5% in autumn, being dominated by Cyclotella, Skeletonema, and Thalassiosira. Dinoflagellates showed similar relative abundance in summer (28.0%) and autumn (28.5%), being dominated by Gyrodinium, Heterocapsa, and Gymnodinium. Four Syndiniales groups (group I-IV) were detected in Sanmen Bay, with higher relative abundance in autumn (10.5%) than in summer (7.6%). Among Syndiniales, group I dominated in summer (49.1%), while group Ⅱ dominated in autumn (75.2%). Salinity, nitrate, nitrite, N:P ratio, and Si:N ratio were identified as the main drivers of the dominant phytoplankton and Syndiniales communities. Network analysis indicated that Syndiniales mainly interacted with diatoms and dinoflagellates, with higher interaction frequency in autumn than in summer. Syndiniales were identified as keystone taxa in the interaction network. Conclusion Seasonal succession of diatoms in Sanmen Bay was more pronounced than that of dinoflagellates. Syndiniales groups I and Ⅱ exhibited significant seasonal succession and maintained close interactions with diatoms and dinoflagellates, serving as key taxa in the interaction network. High-throughput sequencing overcame the limitations of microscopy in detecting Syndiniales, providing systematic insights into the community features and potential interactions of dominant phytoplankton and Syndiniales in Sanmen Bay. This study offers important insights into phytoplankton adaptation and interspecies interactions in eutrophic coastal bays.

Alzheimer’s disease (AD) is a complex neurodegenerative disorder characterized by progressive cognitive impairment. In recent years, the “gut-brain axis” has been recognized to play an important role in the pathogenesis of AD, with the gut microbiota-derived metabolites serving as key mediators of gut-brain communication. This review systematically summarizes the alterations and underlying molecular mechanisms of five classes of key metabolites—short-chain fatty acids, bile acids, indole derivatives, trimethylamine N-oxide, and lipopolysaccharides—during the progression of AD. This review not only provides new perspectives for understanding the pathological processes of AD but also lays a theoretical foundation for the development of diagnostic and therapeutic strategies based on microbiota modulation.

Ciliates of the family Balantidiidae widely parasitize the digestive systems of various invertebrates and vertebrates. Among them, Balantioides coli with cosmopolitan distribution is a major zoonotic pathogen. For a long time, due to the similar morphology of trophozoites of Balantidiidae ciliates from various hosts and the influences of various growing stages and host intestinal microenvironments on morphological characteristics, there have been some inconsistencies and confusions in their classification and nomenclature in literature. Recently, significant progress has been achieved in the study of the phylogenetic relationship and genetic diversity of Balantidiidae ciliates, providing new evidences for their taxonomic reconstruction. On the basis of a systematic review of literature and our findings, this article summarizes the taxonomic status and genetic diversity of Balantidiidae ciliates from different hosts in terms of the morphological characteristics, encystation ability, host specificity, and phylogenetic relationships. The existing evidence supports the division of the family Balantidiidae into two genera Balantidium and Balantioides and indicates that the ciliate infecting humans and various mammals should be classified as Balantioides coli. The related findings and understanding help clarify the taxonomy and nomenclature system of Balantidiidae ciliates and provide an important reference for studying the biological characteristics of Balantidiidae ciliates as well as the diagnosis and control of balantiosis in humans and animals.

Objective To achieve high-level expression and purification of the recombinant 9 kDa and 15 kDa chicken NK-lysin proteins (designated as cNKL9 and cNKL15) and evaluate their in vitro antibacterial and immunomodulatory activities. Methods The target genes—cNKL9 and cNKL15—were individually cloned into the pPIC9K vector to construct recombinant expression plasmids for heterologous expression in Pichia pastoris. After confirming the correct expression of the recombinant proteins via SDS-PAGE and Western blotting, we used nickel affinity chromatography to obtain highly purified recombinant cNKL9 and cNKL15 proteins. The in vitro antibacterial activitiesof recombinant proteins against Salmonella typhimurium and Escherichia coli O157:H7 were assessed by colony forming unit (CFU) assays. We measured the mRNA levels by RT-qPCR and analyzed the transcriptional changes of relevant cytokines after applying the recombinant proteins to the chicken macrophage cell line HD11. High-level expression of the recombinant proteins was achieved in a 15 L fermenter for scale-up culture via optimization of the high-density fermentation process. Results The P. pastoris expression plasmids pPIC9K-cNKL9 andpPIC9K-cNKL15 were successfully constructed. SDS-PAGE and Western blotting results revealed specific bands of recombinant cNKL9 and cNKL15 proteins in the culture supernatant, confirming the successful secretory expression of the target proteins. Antibacterial activity assay demonstrated that the recombinant cNKL9 protein exhibited significant inhibitory activities against both S. typhimurium and E. coli O157:H7, whereas the recombinant cNKL15 protein showed no obvious inhibitory effects on either pathogenic strain. RT-qPCR analysis showed that the recombinant cNKL15 protein significantly upregulated the transcription levels of cytokines such as CCL4 and CCL20 in HD11 cells, while the recombinant cNKL9 protein did not exhibit immunomodulatory activity. Furthermore, in the 15 L fermenter, the heterologous expression yields of cNKL9 and cNKL15 reached 0.64 g/L and 0.53 g/L, respectively. Conclusion For the first time, we achieved high-level expression of recombinant cNKL9 and cNKL15 proteins in the P. pastoris system. Specifically, cNKL9 exhibited inhibitory activities against S. typhimurium and E. coli O157:H7, while cNKL15 exerted immunomodulatory effects by upregulating the mRNA levels of cytokines in the chicken macrophage cell line HD11. These findings provide experimental evidence for the development of cNKL9 and cNKL15 as antibacterial or immunomodulatory agents, indicating their considerable application potential.

Objective Bacillomycin L, a cyclic lipopeptide antibiotic produced by Bacillus velezensis Bs916, has been demonstrated to possess strong antifungal activity. However, its low yield has become a critical bottleneck limiting its large-scale application. This study aims to identify the negative transcriptional regulators involved in bacillomycin L biosynthesis and, based on this, adopt a dual strategy combining genetic engineering and fermentation process optimization to promote its large-scale production. Methods Homologous recombination was employed to construct single (ΔresD, ΔabrB) and double (ΔresDΔabrB) knockout strains. The regulatory characteristics were elucidated by HPLC, inhibition zone measurement, and RT-qPCR. Furthermore, EMSA and DNase I footprinting assays were conducted to investigate the binding activity and identify the specific binding sites of these transcription factors with the flanking sequences of the transcription initiation site of the Bac gene cluster. Finally, fermentation process optimization was performed in a bioreactor to further enhance the production of bacillomycin L. Results HPLC results demonstrated that the bacillomycin L yields of all the mutant strains cultured in the LB media significantly increased by 5.8, 11.3, and 12.0 folds compared with that of the wild-type strain. The antagonistic activities of the mutants against plant pathogenic fungi exhibited corresponding increases. RT-qPCR results further confirmed that both ResD and AbrB acted as negative regulators of bacillomycin L biosynthesis. EMSA experiments revealed that both ResD and AbrB possessed strong binding activities with their target sequences. DNase I footprinting assays further elucidated that AbrB exhibited a propensity for binding to A+T-rich gene fragments and displayed extensive DNA-binding capabilities, directly interacting with the promoter region, 5′ UTR, and coding regions of the Bac gene cluster. Unfortunately, the specific binding site of ResD remained to be identified. Under fermentation conditions, the genetically engineered strain ΔresDΔabrB achieved gram-per-liter level production of bacillomycin L in an optimized glucose-mineral salts medium. This result greatly promoted the large-scale production of bacillomycin L. Conclusion Adopting a dual strategy that combines genetic engineering with fermentation process optimization effectively breaks the bottleneck of low yields for Bacillus-derived antimicrobial peptides. This study provides a reference for the mass production of other microbial secondary metabolites.

Objective To investigate whether cinnamaldehyde affects the acquisition of exogenous plasmids via conjugative transfer in Vibrio harveyi and to elucidate the potential mechanism. Methods V. harveyi 345 was used as the recipient strain, and an Escherichia coli strain harboring the shuttle plasmid pMMB207 served as the donor. The efficiency of exogenous plasmid acquisition by V. harveyivia conjugative transfer was analyzed before and after cinnamaldehyde treatments at three different stages: Treatment 1 (cinnamaldehyde added during the early logarithmic phase of V. harveyi), Treatment 2 (cinnamaldehyde added during the plate-mating process), and Treatment 3 (cinnamaldehyde added during both stages). Changes in biofilm-forming ability of V. harveyi before and after cinnamaldehyde treatments were assessed. Furthermore, qPCR was used to monitor the changes in the expression of quorum sensing (QS)-related genes under Treatment 1 and Treatment 2. Results Cinnamaldehyde at 0.5, 1, 2, 4, and 8 µg/mL reduced the conjugative transfer efficiency by 59%, 98%, 87%, 85%, and 83% under Treatment 1 and by 51%, 85%, 36%, 93%, and 49% under Treatment 2, respectively. Under Treatment 3, cinnamaldehyde at 1, 2, and 8 µg/mL decreased the conjugative transfer efficiency by 71%, 14%, and 75%, respectively. Cinnamaldehyde treatments did not significantly alter biofilm formation. Under Treatment 1, cinnamaldehyde led to no significant changes in the expression of QS-related genes (P>0.05). Under Treatment 2, after 4 h of conjugation, the treatment with 8 µg/mL cinnamaldehyde downregulated the expression of luxM, luxN, luxS, and luxP by 1.47 to 2.94 folds (P<0.05). Meanwhile, treatments with 0.5-8 µg/mL cinnamaldehyde downregulated luxR expression by 1.16 to 3.19 folds (P<0.05). Conclusion Cinnamaldehyde suppresses conjugative plasmid transfer, most likely by attenuating quorum sensing (QS). This study elucidates the role of cinnamaldehyde as a natural compound in regulating bacterial gene transfer and the potential spread of antibiotic resistance, providing a reference for the development of novel antibacterial adjuvants.

Objective To elucidate the tolerance mechanisms of Penicillium oxalicum Z2 to flavonoids present in licorice residues and to analyze its transcriptional responses under gradient stress concentrations, thereby providing a theoretical basis for breeding resistant strains and improving fermentation efficiency. Methods P. oxalicum Z2 was treated with different concentrations of licorice flavonoids (0, 0.25, 0.50, 1.00, and 2.00 mg/mL). Physiological indicators were systematically measured. Transcriptome sequencing was conducted to identify differentially expressed genes and enriched KEGG/GO pathways, revealing the molecular adaptation mechanisms of P. oxalicum Z2 under flavonoid stress. Results As the flavonoid concentration increased, P. oxalicum Z2 maintained high biomass and cellulase activity. Under the highest flavonoid concentration (2.00 mg/mL), its biomass reached 4.840 g/L, and the activities of endoglucanase, β-glucosidase, filter paper enzyme, and xylanase reached 74.78, 3.24, 6.99, and 562.5 U/mL, respectively, which were more than ten folds of those in the conventional P. oxalicum strain. Transcriptome analysis showed that the number of differentially expressed genes increased in a concentration-dependent manner, from 818 in the Low group to 3 945 in the Super group. Under low stress (≤1.00 mg/mL), the strain reprogrammed carbohydrate metabolism and ABC transporter pathways to adjust carbon utilization and sustain essential cellular activities. Under high stress (2.00 mg/mL), it further activated the ribosome and oxidative phosphorylation pathways, with 65 genes upregulated in the ribosome pathway. Conclusion This study identified key genes (e.g., EF-Tu, SecY,and FtsY) and core pathways (e.g., oxidative phosphorylation and ABC transporter), demonstrating that P. oxalicum Z2 employed tiered responses to licorice flavonoid stress. Specifically, the strain remodels sugar metabolism and transmembrane transport under low flavonoid stress to maintain survival and activates ribosome and energy metabolism compensation mechanisms under high flavonoid stress.

To provide valuable information on the current status of research and the hot topics in the field of lactic acid bacteria (LAB) in Baijiu brewing, this study conducted a literature review and screening of relevant publications from 2006 to 2025, based on the China National Knowledge Infrastructure (CNKI) and the Web of Science (WOS) core collection with “Baijiu” and “lactic acid bacteria” as search terms. We employed bibliometrics to analyze the annual number of publications, authors, research institutions, and keyword co-occurrence and bursts of 284 Chinese publications and 324 English publications in this field, and visualized the results in a knowledge map. The results showed that the annual number of publications on LAB in Baijiu brewing exhibited an upward trend overall, with the number of English publications significantly surpassing that of Chinese publications after 2020. Chinese scholars constituted the research mainstream, and XU Yan, ZHANG Suyi, SUN Baoguo and other scholars were major contributors to this research field. Universities such as Jiangnan University, Sichuan University, and Sichuan University of Science and Engineering formed the core research forces, exhibiting a distinct pattern of production-education-research collaboration. Research hotspots gradually shifted from the early isolation and identification of LAB to the in-depth analysis of community structure, dynamic succession, metabolism, and flavor substance formation mechanisms, driven by multi-omics technologies. Future research can focus on the multi-omics mechanisms of LAB, breeding of functional strains, intelligent regulation of synthetic microbial communities, and technological transformation for green brewing to boost the high-quality development of the Baijiu industry. As the first systematic bibliometric and visual analysis of this specific field, this study provides a reference for scholars to grasp the development trends and optimize academic layout, while also offering informational support to promote the scientific and intelligent upgrading of the Baijiu brewing industry.

Objective To investigate the effects of ferric uptake regulator (Fur) on iron homeostasis, oxidative stress response, and virulence in Vibrio parahaemolyticus. Methods BLASTp and multiple sequence alignment analyses were employed to analyze the conservation of Fur proteins in several Gram-negative bacteria. A fur gene deletion mutant (Δfur) and a complementation strain (CΔfur) were constructed. The growth of the wild-type (WT), Δfur, and CΔfur was compared under normal (iron-replete), iron-excess, iron-restricted, and oxidative stress conditions. Inductively coupled plasma mass spectrometry was employed to measure intracellular metal content in each strain. A zebrafish survival assay and a competition infection assay were performed to assess the impact of Fur on the virulence of V. parahaemolyticus. RNA sequencing was conducted to identify the genes regulated by Fur. Results The Fur proteins were highly conserved among several Gram-negative bacteria. The deletion of fur attenuated the growth of V. parahaemolyticus under normal (iron-replete) and iron-excess conditions, and reduced its sensitivity to iron restriction. The intracellular iron content in Δfur was significantly lower than that in the WT and CΔfur strains. Fur regulated the oxidative stress response in V. parahaemolyticus. Fur played no significant role in the virulence of V. parahaemolyticus in the zebrafish model. The expression of multiple genes related to iron uptake, iron storage, and type Ⅲ secretion system 1 (T3SS1) was significantly upregulated, whereas genes encoding iron-containing proteins and type Ⅵ secretion system 2 (T6SS2) components were significantly downregulated in Δfur. Conclusion Fur regulates iron homeostasis and oxidative stress response in V. parahaemolyticus, but does not affect its virulence in zebrafish.

Neurodegenerative diseases, a group of highly prevalent central nervous system disorders, are closely linked to gut microbiota dysbiosis and impaired gut-brain axis function. The emerging gut-brain axis theory offers a novel perspective to explain how microbes exert remote, cross-organ regulation over the central nervous system. Recent studies have indicated that butyrate-producing bacteria, a core functional component of the gut microbiota, exhibit dynamic changes temporally and spatially correlated with the onset and progression of these diseases. These bacteria are thought to modulate the central nervous system microenvironment and disease pathology via the gut-brain axis. This article systematically reviews the bidirectional signaling mechanisms between the gut microbiota and the brain, analyzing the complex, multidimensional relationship between butyrate-producing bacteria and neurodegenerative diseases. This analysis encompasses population heterogeneity in patients with diverse clinical features and the dynamic evolution of these bacterial communities across different disease stages. We summarize the key mechanisms by which butyrate-producing bacteria regulate disease progression, including barrier protection, immunomodulation, metabolic regulation, and epigenetic modification. Furthermore, we explore their clinical potential as predictive biomarkers and therapeutic targets. We propose that future research should prioritize the development of targeted intervention strategies for gut-derived butyrate-producing bacteria. This review aims to provide a theoretical foundation and novel insights to advance both the fundamental investigation and clinical translation of these bacteria in the context of neurodegenerative diseases.