[Objective] To provide a theoretical basis for developing microbiome-based ecological control strategies against citrus Huanglongbing (HLB), a devastating bacterial disease seriously threatening the global citrus industry. [Methods] Rhizosphere soil samples from both HLB-infected and healthy citrus trees in Yizhang County, Hunan Province, were investigated. Using 16S rRNA gene and ITS region amplicon sequencing, we systematically analyzed the impact mechanism of HLB on the rhizosphere micro-ecosystem. [Results] The results showed that HLB infection significantly reduced the organic matter (6.65 g/kg) and available phosphorus (7.25 mg/kg) content of the rhizosphere soil compared with that of the healthy plants, and triggered a significant decrease in the alpha diversity of bacterial communities and a significant increase in the alpha diversity of fungal communities (P<0.05). Beta diversity analysis showed that HLB significantly altered the structure of the microbial communities. Specifically, the relative abundance of pro-biotic bacteria such as Pseudomonadota and Gemmatimonadota decreased, while oligotrophic Acidobacteriota and Chloroflexota were significantly enriched. In fungal communities, the abundance of saprophytic fungi in the phyla Ascomycota and Basidiomycota increased by 5.32% and 7.38%, respectively, while the phylas Rozellomycota and Mortierellomycota decreased by 12.30% and 3.23%, respectively. HLB disrupted the rhizosphere microbial balance by inhibiting Rozellomycota, leading to excessive proliferation of saprophytic fungi and weakening the system’s disease resistance. Analysis at the order level further revealed that beneficial bacterial groups such as Burkholderiales and Hyphomicrobiales were significantly depleted, whereas stress-adaptive groups like Ktedonobacterales showed significant proliferation. PICRUSt2 analysis revealed that HLB disturbed the structure of the citrus rhizosphere bacterial community via metabolic pathways and genetic information processing. HLB also utilized saprophytic and ectomycorrhizal fungi to maintain soil health. [Conclusion] This study revealed that HLB affects soil microecological balance by remodeling the structure and function of citrus rhizosphere microorganisms, and the results may provide a theoretical basis for the development of ecological prevention and control strategies for HLB based on microbiome regulation.

[Objective] To investigate the antifungal activity of Kobusin against Trichophyton interdigitale and its underlying mechanisms. [Methods] The minimal inhibitory concentration (MIC) of Kobusin was determined by the broth microdilution assay. The inhibitory effect of Kobusin on spore germination was observed microscopically, while that on hyphal radial growth was assessed on the agar plates containing Kobusin. Scanning electron microscopy (SEM) was employed to examine the morphological alterations in hyphae. Fluorescence microscopy and nucleic acid and protein leakage assays were employed to evaluated cell membrane integrity. Malvern Zetasizer was used to measure the changes in Zeta potential. A microplate reader was used to measure transmembrane potential, alkaline phosphatase (AKP) activity, malondialdehyde (MDA) content, reactive oxygen species (ROS) accumulation, superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities, mitochondrial membrane potential (MMP), ATP levels, as well as succinate dehydrogenase (SDH) and malate dehydrogenase (MDH) activities. [Results] Kobusin exhibited a MIC of 39 μg/mL against T. interdigitale, significantly inhibiting spore germination and hyphal growth. SEM revealed severe ultrastructural damage to hyphae. Fluorescence microscopy confirmed compromised membrane integrity, evidenced by increased nucleic acid and protein leakage and disrupted Zeta/transmembrane potentials. Meanwhile, Kobusin significantly increased the MDA content and ROS accumulation, inhibited the activities of AKP, SOD, CAT, and POD, markedly reduced MMP, decreased ATP synthesis, and weakened the activities of SDH and MDH. [Conclusion] Kobusin exerts antifungal effects by inhibiting spore germination and hyphal growth, disrupting cell membrane and cell wall integrity, interfering with membrane potential stability, inducing oxidative stress damage, and impairing mitochondrial energy metabolism.

The lined seahorse (Hippocampus erectus) is a major cultured seahorse species with significant economic value in China. Bacterial diseases frequently occur in intensive aquaculture environments, among which skin ulceration is one of the most detrimental diseases affecting H. erectus farming. Skin ulceration is mainly caused by Vibrio spp., while the pathogen complexity and diversity remain unclear. [Objective] This study identified dominant bacterial strains from ulcerative lesions of H. erectus in Zhangzhou, Fujian and characterized their pathogenicity, antibiotic resistance profiles, and virulence traits, aiming to provide a scientific basis for disease prevention and control. [Methods] Bacteria were isolated from ulcerated and internal tissue samples of diseased seahorses. Species identification was performed via morphological observation, physiological-biochemical tests, 16S rRNA gene phylogenetic analysis, and reinfection of seahorses. The isolates were cultured for the measurement of hemolytic activity, caseinase production, and salinity tolerance. Ten virulence genes were detected by PCR. The susceptibility of the isolates to 30 antibiotics was tested via the disk diffusion method. Artificial infection was performed with zebrafish as a model to determine the median lethal dose (LD₅₀). [Results] Fifteen dominant strains were isolated from various tissue samples of diseased seahorses. Among them, three strains (HCE003, HCE070, and HCE098) exhibited β-hemolysis and high overall antibiotic resistance rates (50.0%-56.7%). HCE003 carried vvh, pPHDD1, and hlyAch, while both HCE070 and HCE098 carried hlyA, trh, hlyAch, and vhh. HCE003, HCE070, and HCE098 were preliminarily identified as highly pathogenic strains and were further characterized as Citrobacter freundii, Shewanella algae, and Vibrio rotiferianus, respectively. The three strains were capable of growing normally at the salinity of 15‰. Artificial challenge tests demonstrated that they could induce skin ulceration in H. erectus upon reinfection. The median lethal doses of HCE003, HCE070, and HCE098 in zebrafish were 1.71×10⁵ CFU/mL, 3.68×10⁵ CFU/mL, and 2.51×10⁶ CFU/mL, respectively. [Conclusion] This study is the first to report the isolation of multidrug-resistant and highly virulent C. freundii and S. algae from H. erectus with skin ulceration, indicating that non-Vibrio pathogens can also contribute to skin ulceration in seahorses. These findings provide scientific support for the development of targeted disease management strategies and therapeutic agents in seahorse aquaculture.

[Objective] To explore the changes and differences of gut microbiota of worker bee larvae of Apis cerana cerana and Apis mellifera ligustica after infection with Chinese sacbrood virus (CSBV) and evaluate the antiviral activity of Bacillus subtilis against CSBV. [Methods] Two-day-old larvae of A. c. cerana and A. m. ligustica were collected from colonies and artificially reared in an incubator (34 ℃, RH 85%). The 3-day-old larvae were inoculated with CSBV and samples were collected when the larvae were 4 and 7 days old for 16S rRNA gene sequencing. In addition, the 3-day-old larvae of A. c. cerana were fed with different concentrations of B. subtilis suspensions during CSBV inoculation. When the larvae were 7 days old, the antioxidant capacity indicators malondialdehyde (MDA) content and superoxide dismutase (SOD) activity were determined. Additionally, the relative expression levels of four antimicrobial peptide genes (Abaecin, Apidaecin, Hymenoptaecin, and Defensin) and the CSBV gene were determined by real-time fluorescence quantitative PCR. [Results] The number of gut microorganisms in bee larvae significantly decreased after CSBV infection. The abundance of Bacillus in the gut of 7-day-old A. c. cerana larvae significantly decreased. The gut of A. m. ligustica larvae showed significantly decreased abundance of Streptomyces and significantly increased abundance of Brevundimonas. At 4 days old, CSBV-infected A. c. cerana larvae had significantly higher abundance of Melissococcus in the gut than the infected A. m. ligustica larvae. At 7 days old, CSBV-infected A. c. cerana larvae had significantly lower Chao1 index than the control group and the infected A. m. ligustica larvae, which indicated that the gut microbiota diversity of A. c. cerana larvae was more susceptible to CSBV. The SOD activity of 7-day-old A. c. cerana larvae fed with 1×10⁴ CFU/kg B. subtilis significantly increased, while other doses of B. subtilis had no significant effect on the SOD activity in the larvae. All doses of B. subtilis significantly reduced the MDA content in bees. The relative expression levels of CSBV in the three treatment groups of 1×10⁴, 1×10⁶, and 1×10⁸ CFU/kg were significantly down-regulated. Moreover, the expression level of CSBV in the 1×10⁶ CFU/kg group was the lowest and significantly lower than that in the 1×10⁸ CFU/kg group. However, there were no significant differences in the expression levels of the four antimicrobial peptide genes among different treatment groups. [Conclusion] CSBV infection has a more significant impact on the gut microbiota diversity of A. c. cerana larvae. B. subtilis has a certain inhibitory effect on CSBV.

Peptidoglycan as a key component of the bacterial cell wall is essential for maintaining bacterial morphology and osmotic stability. During normal bacterial growth, peptidoglycan is continuously remodeled through synthesis and hydrolysis, achieving a dynamic equilibrium. Peptidoglycan hydrolases play a central role in regulating peptidoglycan homeostasis, and the hydrolysis products (peptidoglycan fragments) are recycled for biosynthesis via the peptidoglycan recycling pathway. Growing evidence indicates that peptidoglycan fragments function as important signaling molecules to regulate critical physiological processes such as antibiotic resistance, endospore germination, and interspecies interactions, greatly expanding our understanding of bacterial physiological regulation. This review summarizes the major classes of bacterial peptidoglycan hydrolases and highlights recent advances in the role of peptidoglycan fragments as signaling molecules in regulating cellular processes, providing a theoretical foundation for further exploration of the multifaceted physiological functions of bacterial peptidoglycan.

[Objective] The human intestinal tract is rich in microbial resources, which play a significant role in the host’s digestion, absorption, growth, development, etc. Currently, culturomics is widely used in the isolation of beneficial intestinal microorganisms. However, different culture media have preferences, and a single medium is difficult to comprehensively isolate the culturable microorganisms in the intestinal tract. [Methods] We used six reported culture media [brain heart infusion (BHI), Wilkins_Chalgren anaerobe broth (WCBM), (Man-Rogosa-Sharpe) MRS, reinforced clostridial medium (RCM), mucin medium (MM) and modified mucin medium (MMM)] to isolate the microorganisms in the feces of 58 volunteers, with the aim of clarifying the diversity of culturable microorganisms in the intestinal tract and obtaining potential beneficial bacterial strains in the intestinal tract. [Results] A total of 1 052 bacterial strains were isolated from 58 samples, and they were identified as 101 species belonging to 39 genera of 5 phyla. The BHI medium isolated the most bacterial species (50, 49.50%), while the MMM medium isolated the fewest bacterial species (24, 23.76%). Except the MM medium, each of other media could isolate unique genera, and BHI and MMM isolated the most unique genera (5 each). Among the isolated strains, 466 strains were reported to have probiotic effects, including Bacteroides fragilis, Lactiplantibacillus plantarum, Pediococcus acidilactici, and Bifidobacterium bifidum. BHI and MRS media could isolate more beneficial microbial species (10/16, 62.50%). [Conclusion] We explored the diversity of beneficial bacteria in the human intestinal tract from the perspective of pure culture by using multiple culture media, providing rich strain resources for the development of intestinal beneficial microorganisms.

Hyperuricemia is a pathological phenomenon in which the metabolism of uric acid in the human body is disrupted and blood uric acid levels remain above normal. In recent years, gut microbiota has become a research hotspot for various metabolic diseases, serving as a potential new target for the prevention and treatment of hyperuricemia. This article reviews the metabolic pathways and physiological effects of uric acid in the human body and elucidates the regulatory mechanisms of gut microbiota on hyperuricemia. Such mechanisms include inhibiting uric acid synthesis by the breakdown and internalization of purines, degrading uric acid and promoting uric acid excretion, repairing intestinal barriers, influencing intestinal metabolites, and regulating intestinal immunity. In addition, this article summarizes the potential applications of optimizing dietary structure, taking probiotics and prebiotics, and fecal microbiota transplantation in the treatment of hyperuricemia, providing new ideas and references for the prevention and treatment of hyperuricemia.

As a subterranean, soil-dwelling insect, Odontotermes formosanus is susceptible to infection by diverse soil-borne pathogenic fungi. Its symbiotic actinobacteria produce bioactive compounds to combat these pathogens, thereby maintaining a stable symbiotic system of O. formosanus with Termitomyces spp. [Objective] To screen and characterize antifungal metabolites from symbiotic actinobacteria of O. formosanus and to elucidate their defensive role in the termite-fungus symbiotic system. [Methods] Actinobacteria were isolated from O. formosanus-associated samples via diverse culture media. Antifungal strains were screened via dual-culture confrontation assays. The active strain OFGS46 was selected for whole-genome sequencing. Biosynthetic gene clusters (BGCs) were predicted by antiSMASH, and secondary metabolites were analyzed by HPLC-MS. [Results] Twenty-three actinobacteria strains were isolated. Strain OFGS46 exhibited inhibition rates of (62.05±0.98)% against Xylaria sp. and (79.99±0.58)% against Talaromyces sp. Whole-genome sequencing on the Illumina NovaSeq platform yielded approximately 1 Gb of high-quality data. De novo assembly generated a draft genome of 8 470 479 bp. CheckM evaluation demonstrated high assembly quality with 99.91% completeness and 4.63% contamination. HPLC-MS results revealed that strain OFGS46 was capable of producing multiple bioactive secondary metabolites, including enduracidin A, WS9326A, kitacinnamycin A, WAP-8294A2, skyllamycin A, cahuitamycin A, pentamycin, scabichelin, coprisamide C, and frankobactin A1. [Conclusion] This study systematically reveals that the symbiotic actinobacterium OFGS46 from O. formosanus suppresses nest pathogens through the production of diverse antimicrobial compounds. These findings not only elucidate, from a perspective of chemical ecology, the role of symbiotic bacteria in host immune defenses through suppressing multiple pathogenic fungi, but also provide a scientific basis for developing novel antimicrobial resources derived from the termite symbiotic system.

Interferon gamma-inducible protein 16 (IFI16), a pivotal member of the pyrin and hematopoietic expression, interferon-inducible nature, and nuclear localization (HIN) domain-containing protein (PYHIN) family, possesses a unique molecular structure that enables it to recognize diverse nucleic acid molecules within cells. As a key immunoregulatory factor, IFI16 participates in the transduction of innate immune signaling through multiple pathways and plays a significant role in host antiviral defense. This review systematically summarized the molecular characteristics of IFI16 and its regulatory mechanisms in innate immunity and viral infection, aiming to provide a theoretical basis for the development of therapeutic targets and antiviral drugs.

Soil-borne diseases are currently the most significant type of plant disease restricting crop production and threatening food safety. The rhizosphere microbiome, often regarded as the “second genome of plants”, has shown considerable potential in controlling soil-borne crop diseases. The use of rhizosphere microbes to control soil-borne diseases offers many advantages, such as being environmentally friendly, efficient, and broadly applicable, which makes it a hot topic in rhizosphere microbe research. In this review, we first introduced rhizosphere microbes and their potential for controlling soil-borne crop diseases. Subsequently, by integrating the latest research advances, we systematically summarized seven mechanisms of microbial control against soil-borne diseases and categorized them into three pathways: (1) direct interactions between microbes and pathogens; (2) direct and indirect interactions between microbes and plants; (3) indirect interactions among microbes. Furthermore, we reviewed the current applications of the rhizosphere microbes in controlling soil-borne crop diseases. Finally, we analyzed the key research challenges in using rhizosphere microbes for soil-borne disease control and discussed potential solutions, aiming to provide references for advancing the green control of soil-borne diseases.