[Objective] To explore the diversity of culturable bacteria in the mudflat sediments of the Pearl River Estuary in Guangdong Province and to mine strain resources capable of degrading microplastics from these sediments. [Methods] Five media were used for microbial isolation, and phylogenetic analysis was performed by MEGA-X software. The polyethylene terephthalate (PET) medium was selected to screen PET microplastic-degrading strains, and then gene function annotation was performed. [Results] A total of 265 bacterial strains belonging to 71 genera, 32 families of 4 phyla were isolated, including 168 (63.40%) strains of Pseudomonadota, 38 (14.34%) strains of Actinomycetota, 31 (11.70%) strains of Bacillota, and 28 (10.56%) strains of Bacteroidota. Based on the homology of 16S ribosomal RNA (16S rRNA) gene sequences, it was hypothesized that 59 of these strains might be potential new species. From the isolated strains, one PET microplastic-degrading strain was screened. [Conclusion] This study successfully obtained unique microbial resources from the tidal flats of Xiangzhou District, Zhuhai City and one strain capable of degrading PET and using PET as the sole carbon source.

[Objective] To investigate the structural characteristics of microbial communities in the soil samples with varying salt types and their associations with salt ions, thus laying a theoretical foundation for the amelioration of saline-alkali soil. [Methods] Soil samples were collected from three regions: Shijiazhuang (LC), Hengshui (SZ), and Cangzhou (HX) at 38°N. The total soluble salt content (TSS), salt ions, enzyme activities, and microbial community structures were measured. Mantel analysis was performed to examine the correlations between soil salt characteristics and microbial community structures. [Results] In the LC, SZ, and HX regions, the levels of soil electric conductivity, TSS, Na⁺, Cl^-, SO₄^2-, and NO₃^- showed a significant increasing trend, while the activities of four soil enzymes (invertase, alkaline phosphate, urease, and catalase) exhibited significant decreases, indicating that nutrient cycling was inhibited in saline-alkali soil. The β diversity of bacteria and fungi exhibited significant differences among the soil samples of three salt types. The α diversity of both bacteria and fungi in SZ showed significant differences from that in LC. In HX, the abundance of halophilic phyla such as Gemmatimonadota and Myxococcota, as well as the taxa with the function of ureolysis, significantly increased, while that of nitrogen-fixing taxa decreased. Mantel analysis indicated that salt ions such as Na⁺ and Cl^- had significantly negative correlations with microbial community composition but positive correlations with halophilic bacteria, such as Gemmatimonadota. [Conclusion] Microbial communities in the soil samples with different salt types exhibited significant differences. Salt ions drove structural changes of microbial communities in soil by inhibiting non-halophilic microorganisms and selectively enriching halophilic species. The alterations in microbial communities and the reduction in soil enzyme activities are key factors contributing to the impairment of nutrient cycling and supply in saline-alkali soil. This study lays a theoretical foundation for the regulation of key microbial populations in the amelioration of saline-alkali soil.

[Objective] The rhizosphere of plants hosts a diverse array of microorganisms that play a crucial role in plant growth and health. This study identified functional bacteria in the rhizosphere soil of an economic bamboo species Indosasa acutiligulata and assessed the effects of synthetic microbial communities (SynComs) on bamboo growth. The results are expected to provide implications for enhancing forest quality and utilizing beneficial microorganisms in bamboo cultivation. [Methods] Rhizosphere soil samples of In. acutiligulata were collected from the Jiuyi Mountain National Nature Reserve. Bacteria were isolated by the dilution culture method, and a phylogenetic tree was established by the maximum-likelihood algorithm based on 16S rRNA gene sequences. Specific media and colorimetric assays were employed to study the functions of strains. The strains with plant growth-promoting effects and no antagonistic effects between each other were combined. The effects of SynComs on the growth of Phyllostachys edulis seedlings were examined by re-inoculation experiments. [Results] Seventy strains of rhizosphere bacteria were isolated, representing 35 genera belonging to 21 families of four phyla. The dominant phylum was Pseudomonadota and the predominant family was Burkholderiaceae. Functional analyses revealed that 30 strains produced indole-3-acetic acid (IAA), while 16 strains produced siderophores. Among those with dual functions, there were four strains capable of solubilizing inorganic phosphorus, four strains capable of mineralizing organic phosphorus, and three strains capable of solubilizing potassium. Strains TR5, TN6, and TN26 exhibited capabilities to produce IAA and siderophores, as well as solubilize inorganic phosphorus and mineralize organic phosphorus. They were identified as Burkholderia pyrrocinia, Burkholderia paludis, and Paraburkholderia kirstenboschensis, respectively, based on physiological and biochemical properties and 16S rRNA gene sequences alignments. Re-inoculation experiments demonstrated that the SynCom FH, comprising strains TR5, TN6, and TN26, significantly enhanced the root, leaf, and rhizoma growth of Ph. edulis seedlings. [Conclusion] The rhizosphere of In. acutiligulata harbors diverse functional microorganisms capable of producing IAA and siderophores, solubilizing phosphorus, and releasing potassium. The re-inoculation experiments confirmed that the SynCom FH promotes the growth of Ph. edulis seedlings.

[Objective] To establish a theoretical foundation for the application and development of chitinases, this study isolated and screened chitin-degrading bacteria from the intestines of amphibians, optimized their fermentation conditions, characterized their enzymatic properties, and analyzed their whole genomes. [Methods] A strain capable of producing chitinase was isolated from the intestinal contents of Rana kukunoris and identified based on morphological characteristics and molecular biological evidence. The enzyme production conditions of the strain were optimized by single factor and response surface methodology (RSM) experiments, and the enzymatic properties were studied. Whole genome sequencing was carried out for identification of the chitinase gene family. [Results] The chitin-degrading strain JD-3 was identified as Carnobacteriummaltaromaticum. This strain achieved the highest enzyme activity of 12 mU/mL after fermentation with the inoculum amount of 4% at 31.4 ℃ and initial pH 4.9 for 2.47 d. The optimal reaction conditions of the enzyme were 20 ℃ and pH 3.0, and the enzyme maintained good stability at room temperature and under acidic conditions. The genome of JD-3 was 4 195 636 bp long, containing 6 circular contigs, 63 tRNA genes, 19 rRNA genes, and 3 864 protein coding sequences. Two chitinase genes belonging to the glycoside hydrolase family 18 (GH18) were identified and phylogenetically classified into two distinct categories. [Conclusion] We isolated an acid-tolerant chitin-degrading bacterium, C. maltaromaticum JD-3, from the intestines of plateau amphibians. The findings provide new insights into the development and utilization of microbial resources in the digestive systems of animals.

[Objective] To identify the active components in Glycyrrhiza uralensis Fisch. that inhibit methicillin-resistant Staphylococcus epidermidis (MRSE) infections and explore their potential antibacterial mechanisms. [Methods] The half-dilution method was employed to assess the inhibitory activities of pharmacological components from G. uralensis against MRSE. The anti-MRSE phenotype of this medicinal herb was evaluated by microbial adhesion to hydrocarbons, crystal violet staining, scanning electron microscopy, and integrated cell imaging. Additionally, metabolomic analysis was conducted via gas chromatography-mass spectrometry (GC-MS), and the activity of intracellular oxidative dehydrogenase was measured by a commercially available reagent kit. The propidium iodide and laurdan dyes were utilized to assess the membrane damage and fluidity of cells. The challenge test was conducted with the larvae of Galleria mellonella to determine the antibacterial activities of tested pharmacological components in vivo. [Results] Licochalcone A, licochalcone C, and glabridin from G. uralensis demonstrated significantly inhibitory activities against MRSE. Among these compounds, licochalcone A exhibited the strongest inhibitory effect on MRSE, with a minimum inhibitory concentration (MIC) of 6.0 μg/mL and a minimum bactericidal concentration (MBC) of 12.0 μg/mL. The metabolomic analysis indicated that licochalcone A primarily influenced the metabolic pathways, secondary metabolite biosynthesis, and ATP-binding cassette (ABC) transport systems of MRSE. This compound impeded the biosynthesis of ornithine, lysine, and niacin, leading to the accumulation of 1,3-dipalmitin in the cells. Phenotypic experiments corroborated that licochalcone A downregulated the tricarboxylic acid (TCA) cycle flux and reduced the intracellular ATP level in MRSE. Furthermore, it inhibited the biofilm formation and intracellular protein expression, thereby preventing MRSE from adhering to HaCaT cells. Additionally, licochalcone A disrupted the structural integrity of the MRSE cell membrane, resulting in cell collapse, deformation, and even rupture and increased the survival rate of G. mellonella larvae following MRSE infection. [Conclusion] Exposure to licochalcone A alters the metabolism of sugars, lipids, and amino acids in MRSE cells, thereby influencing the biofilm formation, biosynthesis of secondary metabolites such as proteins, and the remodeling of cell membranes. Consequently, this alteration results in an antimicrobial phenotype characterized by decreased ATP production, impaired transporter function, and reduced adhesion and infection of MRSE.

[Objective] To establish a dual detection method for contaminations by six foodborne pathogens (Cronobacter, Escherichia coli O157:H7, Bacillus cereus, Staphylococcus aureus, Salmonella, and Listeria monocytogenes) in formula milk powder in a rapid manner. [Methods] Enzymatic recombinase amplification (ERA) is a novel isothermal amplification technology that exponentially amplifies trace amounts of DNA or RNA in 10-30 min at 25-42 ℃. The primers and probe of ERA for the detection of Cronobacter were designed. Meanwhile, the ERA primers and probes suitable for the detection of E. coli O157:H7, B. cereus, S. aureus, Salmonella, and L. monocytogenes were screened. Further, through pairwise combination and cross-reactivity analysis, as well as method optimization, the dual ERA detection system was established. The limit of detection and accuracy of the method were determined by application of this method in the detection of simulated contaminations and actual samples. [Results] Three groups of dual ERA systems were established, achieving the detection of six pathogens in 16 min 10 s. The established method showed the sensitivity of 1 ng/μL in the DNA detection of the combinations of Cronobacter with E. coli O157:H7, B. cereus, and S. aureus, while it showed the sensitivity of 10^-1 ng/μL in the DNA detection of Salmonella and L. monocytogenes. The results of the simulation contaminations showed that the limit of detection of the method was 1 CFU/mL. The dual ERA method established in this study was then adopted to detect 37 commercially available formula milk powder samples near the expiration date. The detection rates of B. cereus and L. monocytogenes were 37.84% and 21.62%, respectively. The results were consistent with those of the real-time PCR (industry standard method), confirming the accuracy of the dual ERA method established in this study. [Conclusion] The dual ERA method established in this study exhibits high specificity and high sensitivity. Moreover, it takes merely approximately 25 min from DNA extraction to obtaining the detection results, and it is capable of simultaneously detecting six pathogens, demonstrating high efficiency. This method is of importance for the rapid screening of foodborne pathogens.

Honeybees (Apis mellifera) are important pollinators worldwide and models for the research on development and behaviors, showcasing great economic, environmental, and scientific benefits. As the symbiont of honeybees, the gut microbiota is transmitted through social behavioral interactions and plays a crucial role in the development and health of honeybees. It not only helps honeybees digest and absorb nutrients but also helps resist pathogen invasion and enhance immunity. Recently, honeybees have emerged as the models for studying gut microbiota. Researchers not only analyzed the composition and function of the gut microbiota in honeybees but also explored the diversity and functions of strains. This paper reviews the temporospatial dynamics of the gut microbiota in honeybees, the factors affecting the gut microbiota, the influences of the gut microbiota on the biological characteristics and health of honeybees, and the functional applications of the gut microbiota, providing references for the research and application of the gut microbiota in honeybees.

The SaeRS system has been extensively and intensively studied for its involvement in the regulation of virulence factor expression and biofilm formation in the Gram-positive pathogen Staphylococcusaureus, mediating severe pathogenicity. The activation of the system depends on the recognition of external signals by the sensor histidine kinase SaeS and the phosphorylation status of the response regulator SaeR. With the help of auxiliary proteins SaeP and SaeQ, S. aureus is prompted to express a variety of virulence factors, coordinate its biofilm formation, and even evade the host immune response. In addition, other regulatory systems and modulators of S. aureus can synergize with the SaeRS system to participate in the regulation of virulence factor expression, enhancing bacterial pathogenicity. This paper reviews the SaeRS system and its interactions with other regulatory systems and factors to regulate the expression of virulence factors and biofilm formation. It summarizes targeted drugs against the SaeRS system and analyzes specific examples of anti-SaeRS system drugs to provide clues for the screening and design of new targeted drugs. This review is expected to provide a theoretical basis for the research on the specific regulatory mechanisms of the SaeRS system and the treatment of S. aureus-associated infections.

[Objective] To explore the potential mechanism by which Prevotella copri promotes atherosclerosis (AS) from the perspective of host-gut microbiota-metabolism. [Methods] ApoE^-/- mice were randomized into four groups (n=8): control group (Chow group, fed with a normal diet), model group (AS group, fed with a high-fat diet), low-concentration P. copri group (P. copri-low group, administrated with P. copri at 10⁹ CFU/mL by oral gavage daily from the first day of feeding with the high-fat diet), and high-concentration P. copri group (P. copri-high group, administrated with P. copri at 10¹¹ CFU/mL by oral gavage daily from the first day of feeding with the high-fat diet). The body weight was measured and recorded weekly to evaluate the weight gain trend. After 5 weeks, oil red O staining was employed to evaluate the aortic plaque area, and enzyme-linked immunosorbent assay (ELISA) was employed to measure lipid levels, on the basis of which the impact of P. copri on AS progression was assessed. Additionally, qPCR was used to detect the abundance of P. copri in the gut, and untargeted metabolomics was employed to analyze the metabolite changes in the feces of mice. [Results] Compared with the Chow group, the AS group showed increases in the body weight, aortic plaque area, and plasma levels of low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC), and triglycerides (TG) and a decline in the high-density lipoprotein cholesterol (HDL-C) level. The abundance of P. copri in the gut showed no significant difference between the P. copri-low group and the P. copri-high group, indicating that P. copri successfully colonized the gut in both groups. Based on this, the P. copri-low group was selected as the standard concentration group (P. copri group) for further analysis. Compared with the AS group, P. copri colonization in the gut significantly increased the body weight and aortic plaque area and exacerbated dyslipidemia. Metabolomic analysis revealed that P. copri transplantation led to significant increases in the content of several metabolites, including Cer(d18:1/18:1(9Z)), N-palmitoylsphingosine, genistein, adenine, and linoleic acid. KEGG pathway enrichment analysis further indicated that P. copri might contribute to the development and progression of AS through key pathways such as the regulation of ABC transporters, bile acid metabolism, and neuroactive ligand-receptor interactions. [Conclusion] P. copri may exacerbate inflammation and lipid metabolism imbalance by regulating sphingolipid signaling, purine metabolism, and linoleic acid metabolism, thereby promoting the progression of AS.

[Objective] Biofilm formation and adhesion are important indicators for evaluating the beneficial effects of probiotics. However, the relationship of specific genes with the biofilm formation and adhesion of Lactiplantibacillus remains unclear. The rbk gene encodes ribokinase, which is involved in ribose metabolism and may be related to biofilm formation and adhesion. This study aims to analyze the effects of rbk overexpression on the biofilm formation and adhesion of Lactiplantibacillus paraplantrum LR-1, explore the role of this gene in the regulation of quorum sensing (QS) and expression of related genes, and reveal the influencing mechanism of rbk overexpression in bacteria from a metabolic profile perspective. [Methods] L. paraplantarum LR-1 was selected as the target strain, and the shuttle vector pMG76e was used to construct the recombinant strain rbk-pMG76e-LR-1. The overexpression of rbk was confirmed by qRT-PCR and the enzyme activity assay. Crystal violet staining, cell adhesion assay, and qRT-PCR were employed to evaluate the effects of rbk overexpression on biofilm formation, adhesion, and expression of tuf, luxS, and rpoN. Furthermore, untargeted metabolomics analysis was conducted to assess the effect of rbk overexpression on the metabolic profile. Finally, the effect on the biofilm formation and adhesion of LR-1 was verified by exogenous addition of metabolites. [Results] The overexpression of rbk increased the biofilm formation of LR-1 and the adhesion to HT-29 cells by 1.55-2.34 folds and 3.58 folds, respectively. Moreover, the overexpression of rbk up-regulated the expression levels of tuf, luxS, and rpoN by 70.30, 96.94, and 45.61 folds, respectively. The untargeted metabolomics analysis revealed that rbk overexpression led to changes in the abundance of 145 metabolites. Finally, the exogenous addition of l-proline, rhamnose, and nicotinamide adenine dinucleotide (NADH) increased the biofilm formation of LR-1 by 1.27, 1.39, and 1.25 folds and the adhesion by 1.40, 1.41, and 1.52 folds, respectively. [Conclusion] This study demonstrates that rbk can serve as a key target for enhancing the biofilm formation and adhesion of Lactiplantibacillus.