Zearalenone (ZEN) is a secondary metabolite produced by the filamentous fungi of Fusarium, causing serious harm to human and animal health. [Objective] To identify a ZEN-degrading strain and investigate its growth and degradation characteristics under different conditions. [Methods] A bacterial strain that can efficiently degrade ZEN was screened out with ZEN as the only carbon source from soil samples of a field with continuous maize cropping in Anhui Province, China. The strain was identified by morphological observation, biochemical tests, and phylogenetic analysis based on 16S rRNA gene sequences. The effects of temperature, pH, and incubation time on the growth rate and ZEN degradation efficiency of the strain were studied. Furthermore, the efficiency of different active components of the strain on ZEN degradation was measured, and the locations of the active components were determined. [Results] A total of 21 ZEN-degrading strains were isolated from the soil samples, among which strain DC-R2 showed the strongest degradation effect and it was identified as Gordonia sp. BHI medium was the optimal medium for the growth of this strain. The optimal culture conditions of the strain for ZEN degradation were 37 ℃ and pH 8.0, under which 100% ZEN (5 μg/mL) was degraded within 6 h. Intracellular enzymes were the main contributors in DC-R2 to ZEN degradation. [Conclusion] We isolated a strain Gordonia sp. DC-R2 capable of efficiently degrading ZEN. The intracellular enzyme present in this strain is the key to the degradation of ZEN. This provides a foundation for the purification of the key degrading enzyme in subsequent work and the potential application.

Heavy metal pollution has attracted increasing attention because of its toxicity, environmental persistence, bioaccumulation, and potential contribution to antibiotic resistance. The accurate, rapid, efficient, and sensitive detection of heavy metals in the environment is of great significance for environmental protection and human health. A whole-cell microbial biosensor (WCMB), integrating a biorecognition module and a signal processing module, provides a new strategy for heavy metal monitoring. Great progress has been achieved in the transcription factor-based WCMBs for the monitoring of heavy metals in recent years. This paper introduced the basic composition and design principles of WCMBs, summarized the construction and application of WCMBs for heavy metal detection that were developed in recent years, analyzed the optimization strategies of WCMBs by synthetic biology, and finally prospected the future research directions of WCMBs. This paper is expected to be an important reference for the effective prevention and control of heavy metal pollution in the environment.

[Objective] To develop a safe, effective, and identifiable new vaccine. [Methods] The gene deletion strain S2Δbp26 was constructed by homologous recombination with S2 as the parental strain. The stability, safety, and efficacy of S2Δbp26 were then evaluated. [Results] The phenotype and genotype of S2Δbp26 did not change after 20 successive passages invitro. The experiments in mice and guinea pigs showed that there was no difference in biosafety between S2Δbp26 and S2. The bacterial load was less than 2×10⁵ CFU per gram of spleen in guinea pigs inoculated with S2Δbp26 at different passages and S2, which suggested that the virulence of the mutant strain was attenuated. The mice inoculated with S2ΔBP26 had a shorter 50% recovery time than those inoculated with S2. Meanwhile, the mice immunized with S2Δbp26 could successfully resist the challenge with M28 wild-type strain at a dose of 2×10⁵ CFU/mouse. [Conclusion] S2Δbp26 was successfully constructed, with excellent safety and immunoprotective capacity, which provided technical reserves for the development of identifiable vaccines for brucellosis.

In the special environment of plateau, adaptive responses and pathological changes occur in the skin of organisms, which include skin barrier dysfunction, skin vasoconstriction disorder, abnormal thickening of the stratum corneum, and fibrous pigment deposition, leading to a high incidence of skin diseases in plateau areas. In the plateau environment, the composition and diversity of skin microbiota change, which may be related to the occurrence and development of skin diseases. This paper reviews the effects of plateau environments on the skin, common skin diseases in plateau environments, and the effects of skin microbiota on skin diseases and discusses the mechanisms by which skin microbiota influences skin diseases in plateau environments.

Cotton Verticillium wilt is the most serious disease affecting cotton cultivation, which could cause a significant decrease in cotton yield or even complete crop failure. Cotton Verticillium wilt is caused by the filamentous fungus Verticillium dahliae. The traditional chemical control affects public health and brings about environmental pollution, and the continuous usage has induced the drug resistance of Verticillium dahliae. Therefore, it is urgent to develop environmental friendly and sustainable development control strategies against cotton Verticillium wilt. Biological control has become a good choice to prevent cotton Verticillium wilt. Based on the analysis of the recent research progress, this review discussed the screening, mechanism of action and field application of biocontrol microbial strains against cotton Verticillium wilt, and summarized the research progress of biocontrol microorganisms inhibiting the growth of pathogen through various mechanisms such as competition, antibiotic action, and inducing plant defense response. Although the application prospects of biocontrol microorganisms are expected, they still face challenges such as environmental adaptability, stability, and usage costs of these biocontrol microorganisms. To further improve the practicality of biocontrol microbial strains in agricultural production, future research should focus on genetic improvement of biocontrol microorganisms, development, and application of the microbial agents and so on.

[Objective] The biological regulatory mechanisms of soil microorganisms in response to single heavy metals or organic pollutants have been extensively studied, while the biological mechanisms of microbial responses to combined pollution remain unclear. This study aims to reveal the biological mechanisms of Enterococcus faecalis HHT-1 in response to single and combined stress of cadmium (Cd) and aniline (AN) by transcriptomics. [Methods] Transcriptomics was employed to explore the transcriptional regulation of HHT-1 under single (Cd: 150 mg/L; AN: 2 g/L) and combined stress (150 mg/L Cd and 2 g/L AN) at half inhibitory concentrations (IC₅₀). [Results] Under single Cd stress, HHT-1 upregulated the expression of genes encoding metal-binding proteins and transporters to promote the sequestration or efflux of Cd²⁺. High concentrations of Cd induced oxidative stress in cells, and HHT-1 upregulated the expression of ribosome-related genes and nucleotide-related genes to repair the protein damage and DNA damage caused by oxidative stress, and cleared intracellular reactive oxygen species (ROS) by producing catalase. Moreover, Cd stress upregulated the expression of genes related to virulence and antibiotic resistance in HHT-1. Under the single stress of AN, HHT-1 activated the expression of AN-degrading enzyme genes to reduce its toxicity and upregulated the expression of genes encoding efflux pumps to excrete AN from the cell. AN also caused intracellular oxidative stress, and HHT-1 cleared the ROS by upregulating the expression of glutathione synthase genes. Under the combined stress of Cd and AN, HHT-1 exhibited a complex array of adaptive mechanisms. Initially, HHT-1 upregulated the expression of genes encoding metal transporters and efflux pumps to transport Cd and AN out of the cell, thereby mitigating their toxic effects on the cell. At the same time, HHT-1 cleared intracellular ROS via the dual pathway of catalase and glutathione. In addition, HHT-1 upregulates the expression of virulence and antibiotic resistance genes under combined stress, which may enhance its pathogenicity and resistance. It is worth noting that HHT-1 did not significantly upregulate the expression of AN-degrading enzyme-related genes under the combined stress. [Conclusion] The transcriptional regulation mechanism of E. faecalis HHT-1 in response to the combined stress of Cd and AN is a combination of the transcriptional regulation mechanisms observed under single Cd stress and single AN stress, and it is more similar to the mechanism observed under single Cd stress. HHT-1 mainly responds to the combined stress of Cd and AN by enhancing cell wall synthesis, Cd²⁺ efflux, DNA repair, and ROS scavenging. Genes associated with efflux pumps and glutathione under AN stress continue to be expressed under the combined stress. Both single Cd stress and combined stress of Cd and AN may increase the potential pathogenicity and drug resistance of HHT-1.

[Objective] To study the probiotic properties and safety of Limosilactobacillus reuteri CHF7-2 isolated from Chahua chicken, providing a theoretical basis for the development of this strain as a microecological feed additive. [Methods] In vitro assays were conducted to evaluate the adhension, enzyme production, antibacterial activity, and antioxidant activity of strain CHF7-2. PacBio Sequel II and Illumina NovaSeq 6000 were used for whole genome sequencing of strain CHF7-2. Bioinformatics tools and databases were then used for genome annotation to explore the probiotic mechanisms and safety of this strain at the molecular level. [Results] Strain CHF7-2 possessed significant probiotic properties and safety. It exhibited high surface hydrophobicity, self-coagulation, and antioxidant activity. The strain inhibited the growth of Escherichia coli K88, Staphylococcus aureus ATCC 49521, Salmonella gallinarum CICC 21510, and Salmonella choleraesuis CVCC 3383. Strain CHF7-2 produced protease and lipase, and it was safe for use in feed since it did not exhibit hemolytic activity. Whole genome sequencing revealed that the genome size of CHF7-2 was 2 116 761 bp, with the G+C content of 38.8%, encoding 2 067 genes. Additionally, the genome carried the biosynthetic gene cluster of the class III bacteriocin EnlA and multiple genes involved in the acid tolerance, bile salt tolerance, heat stress tolerance, cold stress tolerance, adhesion, antioxidation, and organic acid synthesis, with no virulence or antibiotic resistance genes detected. [Conclusion] L. reuteri CHF7-2 is a potential probiotic strain and a promising candidate for use as a microecological feed additive.

[Objective] To evaluate the colonization ability and biocontrol effects of Streptomyces sp. ZH-356 with antagonistic effects on plant pathogenic fungi and reveal the biocontrol mechanism of Streptomyces sp. ZH-356 by omics analysis. [Methods] The colonization of Streptomyces sp. ZH-356 in plants was detected by the GFP fluorescent labeling method. The biocontrol effects and potential of Streptomyces sp. ZH-356 on plant fungal diseases were evaluated based on the biocontrol effects of the inoculant in different dosage forms (seed coating agent, wettable powder, gum inoculant, and bone glue inoculant). The whole genome information of Streptomyces sp. ZH-356 was analyzed by third-generation sequencing, and its gene functions were annotated. The comparative transcriptome analysis was performed to screen the differentially expressed genes during the antagonizing process of Streptomyces sp. ZH-356 against plant pathogenic fungi, and thus the genes involved in the synthesis of antagonistic substances were predicted. [Results] Streptomyces sp. ZH-356 stably colonized the roots and stems of tomato and wheat plants. Different dosage forms of inoculants prepared based on Streptomyces sp. ZH-356 demonstrated strong control effects on tomato early blight and apple valsa canker. Among them, the seed coating agent prepared with Streptomyces sp. ZH-356 did not affect the germination rate of tomato seeds after treatment while protecting tomato seedlings from the infection of Alternaria solani. The wettable powder prepared with Streptomyces sp. ZH-356 showed both prevention and treatment effects on tomato early blight, with the prevention effect stronger than the treatment effect. The liquid inoculants prepared from Streptomyces sp. ZH-356 had control effects on apple Valsa canker, regardless of whether the diseased bark was scraped or not, while the control effect was better when the diseased bark was scraped and better than that of thiophanate-methyl. The whole genome sequencing results showed that Streptomyces sp. ZH-356 contained only one linear chromosome with a size of 9 435 898 bp and the average G+C content of 70.82%. A total of 8 432 coding genes, 69 tRNA genes, and 18 rRNA genes were predicted. Species annotation results showed that Streptomyces sp. ZH-356 did not belong to any Streptomyces species whose genome has been sequenced. Genome-wide analysis showed that there were 32 biosynthetic gene clusters (BGCs) for secondary metabolites in ZH-356. Transcriptomic analysis showed that the expression of the NRPS/T1PKS gene cluster ZH_356_GM000343-ZH_356_GM000422 was significantly up-regulated in the process of antagonizing plant pathogenic fungi, suggesting that it may be a BGC mediating the biosynthesis of active substances against plant pathogenic fungi in Streptomyces sp. ZH-356. Moreover, ZH_356_GM000409 may be the core biosynthetic gene of the active substances. [Conclusion] Streptomyces sp. ZH-356 can colonize plants, and the biocontrol agents prepared based on this strain demonstrate good control effects on plant fungal diseases. The active substances for the antagonistic effects may be synthesized by the gene cluster ZH_356_GM000343-ZH_356_GM000422. The above work lays a foundation for the industrial application of strain ZH-356 and the research on the mechanism of antagonizing plant pathogenic fungi.

[Objective] To identify mazEF family type II toxin-antitoxin systems of Leuconostocpseudomesenteroides L64 and to elucidate the molecular roles of the mazEF systems in the host exposed to environmental acid stress. [Methods] Putative MazF toxins were induced alone or co-expressed with their cognate antitoxins in Escherichiacoli. The toxic effect of MazF on bacterial growth and the antitoxic effects of cognate antitoxins were examined. The lacZ reporter system and electrophoretic mobility shift assay (EMSA) were used to decipher the auto-regulation mechanism of the mazEF system invivo and invitro. The putative target genes regulated by MazE were predicted and validated through invivo and invitro experiments. [Results] Among the three putative mazEF systems in L. pseudomesenteroides L64, mazEF1-Leup (OYT_01690-OYT_01685) encoded a functional type II toxin-antitoxin system. MazE1-Leup (OYT_01685) inhibited mazEF1-Leup transcription by binding to the palindromic sequence (TAACAaaatgTGTTA) in the promoter. In addition, MazE1-Leup inhibited transcription of the dlt-acpS-alr operon by binding to the similar palindromic sequence (TAACAtattgaaatatatgTGTTA) in the promoter of dlt-acpS-alr. [Conclusion] mazEF1-Leup (OYT_01690-OYT_01685) encodes a functional mazEF family type II toxin-antitoxin system. Beyond regulating its own operon, MazE1-Leup regulates the transcription of dlt-acpS-alr and finally assists L. pseudomesenteroides L64 in response to low acid stress.

[Objective] To investigate the effects of Weizmannia coagulans BC-G44 on the intestinal microbiota structure, barrier function, and inflammatory response in the colon of the rat model of antibiotic-associated diarrhea (AAD). [Methods] A total of 30 five-week-old Sprague-Dawley (SD) rats with similar body weights were randomized into five groups (n=6): control (Con), model (Mod), low-dose W. coagulans BC-G44 (LBC-G44), medium-dose W. coagulans BC-G44 (MBC-G44), and high-dose W. coagulans BC-G44 (HBC-G44). The experiment encompassed a modeling period (7 days) and a recovery period (12 days). During the modeling period, rats in the Con group were administrated with normal saline at 2 mL/d by gavage, while those in the Mod, LBC-G44, MBC-G44, and HBC-G44 groups were administrated with a mixture containing clindamycin, ampicillin, and streptomycin (2 mL/d) by gavage to induce AAD. During the recovery period, the Con and Mod groups continued to receive normal saline, while the LBC-G44, MBC-G44, and HBC-G44 groups received W. coagulans BC-G44 suspensions at 10⁷, 10⁸, and 10⁹ CFU/d, respectively. On day 19, colonic tissue samples were collected for histological examination, and the concentrations of cytokines, and the expression levels of barrier proteins and inflammation-related genes in the colonic mucosa were measured. Furthermore, the microbiota composition and metabolites in the colonic chyme were analyzed. [Results] On day 7 of modeling, rats in the Mod, LBC-G44, MBC-G44, and HBC-G44 groups exhibited diarrhea, weight losses, and reduced food intake compared with those in the Con group (P<0.05). On day 19, compared with the Mod group, the MBC-G44 and HBC-G44 groups showed increases in the colonic mucosa thickness and goblet cell number (P<0.05). The HBC-G44 group showed increased relative abundance of Bacteroides and concentrations of lactate in the colonic chyme (P<0.05), elevated levels of d-lactic acid (d-LA) and diamine oxidase (DAO) in the colonic mucosa, and up-regulated relative mRNA levels of Claudin-1, Occludin, and MUC2 in the colonic mucosa (P<0.05). Meanwhile, compared with the Mod group, the MBC-G44 and HBC-G44 groups showed down-regulated relative mRNA levels of Toll-like receptor 4 gene (TLR4) and nuclear factor-kappa B gene (NF-κB) (P<0.05), and reduced concentrations of tumor necrosis factor (TNF)-α and interleukin (IL)-1β (P<0.05) in the colonic mucosa. [Conclusion] W. coagulans BC-G44 can ameliorate antibiotic-induced colonic injury, regulate the colonic microbiota composition and metabolites, enhance intestinal barrier function, and reduce intestinal inflammatory responses in rats, thus alleviating the symptoms of AAD.