Phenolic acids autotoxic substances secreted by plant roots, such as p-hydroxybenzoic acid (PHBA), are the main factors causing continuous cropping obstacles in plants. [Objective] In order to obtain PHBA degrading bacteria and improve its degradation efficiency. [Methods] A PHBA-degrading strain was isolated by screening medium and inorganic salt medium, and it was identified asMicrobacterium aurantiacum. The initial content of PHBA, culture temperature, pH and nitrogen source were optimized by single factor experiment and response surface methodology. [Results] The highest degradation rate was obtained when the PHBA content was 0.4 g/L, the temperature was 30 ℃, the pH was 8.0, and the nitrogen source was ammonium sulfate. The optimal degradation conditions were temperature 30.2 ℃, pH 8.3, and PHBA concentration 0.18 g/L, and the degradation rate reached 100%. Combined with pot experiments and high performance liquid chromatography, the results showed that the strain could effectively mitigate the PHBA stress effect in cucumber rhizosphere. [Conclusion] The strain ofMicrobacterium aurantiacum screened in this study has a high ability to degrade PHBA, and has the potential value in continuous cropping obstacles.

The proposal of ban on antibiotics in feed is a turning point for the animal husbandry, marking that the feed industry and animal husbandry have entered a new stage of transformation and upgrading. [Objective] To investigate the effects of addingBacillus licheniformis HDTN to feed on the growth performance and intestinal flora of '817' broilers. [Methods] B.licheniformis HDTN powder (7.0×10¹⁰ CFU/g) was added to the feed for '817' broilers. The effects of high-, medium-, and low-dose (1 000, 500, and 250 g/t) bacterial addition on the growth performance, serum biochemical indexes, intestinal morphology, and intestinal flora structure of the '817' broilers during 1–56 days were studied, with the group without bacterial addition as the control. [Results] Compared with the control group, the addition of low-doseB.licheniformis HDTN increased the average body weight by 105.47 g (P < 0.01) and reduced the feed-to-weight ratio by 0.25 (P < 0.05) during days 1–35. The antioxidant indexes in the broiler serum were positively correlated with the dose of HDTN, which reduced oxidative stress in broilers. The content of malondialdehyde was negatively correlated with the dose of HDTN, which suggested that HDTN reduced cellular damage in broilers. The ratio of villus height to crypt depth in the duodenum of the low-dose group was higher than that of the control group (P < 0.01). In addition, compared with the control group, medium-dose (P < 0.01) and low-dose (P < 0.05) groups showed increased relative abundance ofFirmicutes, and the medium-dose group showed increased relative abundance ofBacteroides (P < 0.05). [Conclusion] Addition of low-doseB.licheniformis HDTN for '817' broilers can improve the growth performance, reduce the feed-to-weight ratio, improve the intestinal morphology, and accelerate the assembly of intestinal flora during days 1–35.

[Objective] To construct a recombinant food-and-mouth disease virus (FMDV) strain carrying the genes encoding three topotypes of immunodominant structural proteins of serotype O FMDV by reverse genetic manipulation and evaluate the potential of the recombinant strain serving as a vaccine candidate for porcine food-and-mouth disease (FMD) type O. [Methods] Based on the gene of the recombinant FMDV with the replacement of the VP1 structural protein of O/NXYCh/CHA/2018 epidemic strain, the recombinant full-length plasmid featuring substitution of G-H loop genes of the structural protein VP1 of O/TUR/5/2009 vaccine strain was constructed by gene synthesis. The recombinant virus was rescued after transfection of the linearized recombinant plasmid into BSR/T7 cells expressing T7 RNA polymerase, and then identified by RT-PCR, sequencing, and indirect immunofluorescence. The plaque assay and one-step growth curve building were employed to characterize the recombinant virus. Pigs were vaccinated with the vaccines prepared from the recombinant virus and the parental virus, and then virus neutralization tests were carried out to examine the cross-reactive responses against the epidemic serotype O FMDV isolates of three topotypes. [Results] The recombinant FMDV strain carrying the structural protein genes of three topotypes was successful rescued. The recombinant strain showed similar biological properties to the parental virus. Pigs vaccinated with the vaccines prepared from the recombinant virus and the parental virus produced protective neutralizing antibodies with the mean titer of > 1.65log₁₀ against the viruses of the Middle East-South Asia (ME-SA) and South-East Asia (SEA) topotypes. The pigs did not produce protective neutralizing antibodies against the Cathay topotype (< 1.65log₁₀). The substitution of O/TUR/5/2009 G-H loop gene improved the cross-reactivity against the viruses of ME-SA and SEA topotypes compared with the parental virus (P < 0.05). [Conclusion] This study has guiding significance for the design of FMD vaccines in the future.

[Objective] High-temperature stacking fermentation is a key process in the production of Jiang-flavor Baijiu.Kroppenstedtia is a predominant bacterial genus in the stacked fermented grains, and investigating its growth and metabolic characteristics contributes to comprehensively understanding the crucial role of stacking fermentation. [Methods] The tryptic soy broth was used to screenKroppenstedtia strains from the stacked fermented grains, and the taxonomic status of each strain was determined by morphological observation and 16S rRNA gene sequencing. Furthermore, the growth characteristics and volatile compound metabolism of each strain were investigated by solid-state fermentation experiments on sorghum at different temperatures (45 ℃ and 50 ℃) in combination with pure culture. [Results] Three strains ofKroppenstedtia were isolated from the fermented grains of Jiang-flavor Baijiu and identified asK.eburnea. The liquid culture of strainK.eburnea 1613 significantly enhanced the production of pyrazines, which was 2.66 folds of that in the control group. The volatile compounds of sorghum in solid-state fermentation predominantly consisted of alcohols and acids, the total content of which increased over the fermentation time. The fermentation at 50 ℃ promoted the accumulation of alcohols, acids, and pyrazines, and that at 45 ℃ facilitated the accumulation of esters. The primary metabolites produced by the three strains during solid-state fermentation with sorghum as the substrate were phenethyl alcohol and isovaleric acid. The fermentation withK.eburnea 1615 at 50 ℃ for 15 days produced the highest levels of phenethyl alcohol and isovaleric acid, which reached (31.17±0.14) µg/g and (16.75±0.76) µg/g, respectively. The fermentation withK.eburnea 6E22 andK.eburnea 1613 at 50 ℃ yielded the highest levels of 2, 5-dimethyl pyrazine [(1.67±0.14) µg/g] and hexanoic acid [(3.74±0.19) µg/g], respectively, after 15 days. The accumulation of aldehydes and ketones was significant in sorghum fermented at 50 ℃. The partial least squares-discriminant analysis (PLS-DA) revealed significant influences of temperature and time on the volatile compound composition of sorghum fermented by the three strains. [Conclusion] K.eburnea contributes to the production of flavor compounds in fermented grains, particularly the characteristic flavor compounds such as alcohols, acids, and pyrazines of Jiang-flavor Baijiu.

[Objective] To reveal the composition and functions of endophytic bacterial communities in maize under different patterns of tillage combined with straw returning in the Tumochuan Plain, identify the endophytic bacterial resources that promote maize straw degradation under different patterns, and lay a foundation for the selective isolation, cultivation, and functional verification. [Methods] We employed Illumina MiSeq high-throughput sequencing to compare the diversity and community structure of endophytes during the mature stage of maize under different patterns of tillage combined with straw returning in the continuous positioning experiment in the irrigation area of Tumochuan Plain, Inner Mongolia Autonomous Region. [Results] No tillage and deep tillage demonstrated significant effects on the endophytic bacterial diversity of maize. Tillage methods exerted stronger effects on the composition and structure of endophytic bacterial community than straw returning. The structures of endophytic bacterial communities in maize can be classified into two categories: no tillage combined with straw returning and the other seven patterns. The dominant endophytic bacterial genera shared by the nine patterns of tillage combined with straw returning werePseudomonas, unclassified_f__Enterobacteriaceae,Pantoea,Raoultella, andRahnella1. Straw returning increased the abundance ofRaoultella and unclassified_f__Enterobacteriaceae. [Conclusion] Different tillage practices alter the diversity, composition, and structure of endophytic bacterial community in maize. Straw returning can increase the relative abundance ofRaoultella andLactococcus, which have positive effects on the degradation of maize straw.

L-asparaginase, a key enzyme in amino acid metabolism, is widely used in the food and pharmaceutical industries. The gut microbiota and its product L-asparaginase are closely associated with host health and diseases. [Objective] This study aims to acquire a novel L-asparaginase gene from gut microbiota and explore its enzymatic characteristics and potential applications. [Methods] An L-asparaginase gene was cloned from the metagenome of the fecal microbiota ofNomascus concolor and heterologously expressed inEscherichia coli BL21(DE3). The enzymatic properties of the expressed protein were determined. Furthermore, the potential applications of this protein were explored, including processing potato chips and treating cancer cells. [Results] The cloned L-asparaginase gene,NCasn5, was 996 bp. It encoded the recombinant enzyme NCasn5 with a molecular weight of 37.296 kDa, optimal activity at pH 8.0 and 60 ℃,K_m of (3.33±0.21) mmol/L,V_max of (836.30±13.91) µmol/(min·mg), and a serum half-life of about 69 hin vitro at 37 ℃. NCasn5 reduced the acrylamide content in potato chips by 69.35% and inhibited the growth of human liver cancer cells (QGY-7703) and human melanoma cells (A-375). [Conclusion] We obtained a novel L-asparaginase demonstrating good thermal stability and a prolonged serum half-life. This enzyme lacks the glutaminase activity and reduces acrylamide levels in potato chips. Moreover, it can induce apoptosis in the cancer cell lines QGY-7703 and A-375. These findings suggest the potential applicability of L-asparaginase in both food processing and pharmaceutical industries.

[Objective] To develop a stable and controllable method for isolating and cultivating the eukaryotic microorganismEntodiniumcaudatum from the rumen of ruminants, which would lay a foundation for the germplasm banking and provide sufficient experimental materials for researching the physiological function of rumen ciliates. [Methods] First, a rumen cannula was used to collect rumen fluid from cows in Wuhan, andE.caudatum was gradually enriched and isolated from the rumen fluid by micro-strainer filtration through different sizes of nylon mesh. Subsequently, the enrichedE.caudatum was cultured in anaerobic culture bottles loaded with the modified SP medium. After purification, a single culture of the strain was established. The species was identified by morphological observation and the phylogenetic analysis based on the 18S rRNA gene. Finally, the generation time of theE.caudatum was calculated based on the half-transfer cultivation method. [Results] A single culture ofE.caudatum was isolated from the rumen fluid of Holstein cows. The modified SP medium used in this study was composed of SP salt solution, supernatant of the rumen fluid without protozoa, cysteine hydrochloride, antibiotics, starch, and grass powder. In the modified SP medium, the obtained culture grew and proliferated steadily, reaching the highest density of 37 000 cells/mL on day 16 from the initial inoculation density of 320 cells/mL. Morphological features and molecular data indicated that the culture obtained in this study wasE.caudatum, namedE.caudatum strain WH. The generation time ofE.caudatum strain WH was 19.0 h. [Conclusion] This study has successfully developed aninvitro cultivation method forE.caudatum strain WH, a prevalent eukaryotic microorganism from the rumen of ruminants. This work lays a technical and theoretical basis for the germplasm banking and in-depth research on the physiological functions of rumen ciliates.

Arbuscular mycorrhizal fungi play important roles in ecosystems and plant growth. The physiological and ecological roles of arbuscular mycorrhizal fungi, especially in promoting plant growth, have attracted much attention. The colonization characteristics of arbuscular mycorrhizal fungi, as vital indicators of the symbiotic relationship between arbuscular mycorrhizal fungi and plants, are key parameters to evaluate the ecological adaptability of plants. However, systematic and comprehensive studies remain to be carried out regarding the colonization characteristics of arbuscular mycorrhizal fungi in the plants growing in China. [Objective] This study explored the colonization parameters of arbuscular mycorrhizal fungi in the plants growing in China, as well as their distribution in different ecosystems and climate regions, aiming to provide fundamental data to advance the research on mycorrhizae. [Methods] A database of arbuscular mycorrhizal fungi colonizing plants growing in China was established with the data from FungalRoot and 605 Chinese papers. Furthermore, the database was supplemented with 47 700 data sets including mycorrhizal colonization characteristics, ecosystem types, climate regions, plant types, and plant growth years. The analysis in this study was then performed based on this database. [Results] In China, 69.7% and 30.3% plants exhibited the arbuscular mycorrhizal fungal colonization rates ranging from 0 to 55% and from 55% to 100%, respectively. The majority of plants showed the arbuscular mycorrhizal fungal colonization intensity, hyphal abundance, vesicular abundance, and arbuscular abundance below 40.0%. Among the symbiotic forms of arbuscular mycorrhizal fungi, type A was the most prevalent, existing in 56.3% plants. Arbuscular mycorrhizal fungi demonstrated similar colonization rates in farmland, desert, and grassland ecosystems (51.8%, 51.6%, and 51.8%, respectively) and a low colonization rate (40.4%) in forest ecosystems. The plants in desert ecosystems showcased the highest arbuscular mycorrhizal fungal colonization intensity, hyphal abundance, vesicular abundance, and arbuscular abundance, which reached 46.0%, 47.1%, 37.2%, and 31.2%, respectively. In different climate regions, the colonization level followed the trend of warm temperate zone (53.3%) > tropical zone (50.0%) > temperate zone (45.2%) > subtropical zone (42.2%). The colonization level was higher in herbaceous plants than in woody plants, and higher in perennial plants than in annual plants. Among woody plants, shrubs had the highest colonization rate at 46.3%, followed by trees and vines, both at 43.9%. Herbaceous plants had higher colonization intensity (30.2%) and hyphal abundance (32.5%) than woody plants, while woody plants had higher vesicular abundance (19.5%) and arbuscular abundance (23.4%). Among the plants colonized by arbuscular mycorrhizal fungi, angiosperms accounted for the majority (90.2%, belonging to 110 families), while ferns, gymnosperms, and lycophytes were less common. [Conclusion] In China, arbuscular mycorrhizal fungi showed the colonization rate below 55% and colonization indicators below 40.0% in most plants. Different ecosystems, climate regions, plant types, and plant growth years affected the colonization status to different degrees.

Innate immunity constitutes the first line of immune defense. As a part of the body's innate immunity, the antimicrobial peptide LL-37 plays a crucial role in maintaining homeostasis, with two primary functions: direct antimicrobial activity and immunomodulation. Currently, research on LL-37 mainly focuses on its function, while its induced expression in vivo has rarely been studied. However, understanding the induced expression of LL-37 is essential for delving into the body's immune defense mechanisms. Therefore, this paper briefly reviewed the research progress on the synthesis and functions of LL-37, the factors inducing its secretion, and the regulatory pathways involved in its induced expression. The aim is to offer new insights into the regulatory pathways and immune defense functions of LL-37 in the human body.

[Objective] To study the transcriptome regulation mechanism of Fusarium graminearum under different pH stress conditions, analyze the changes in gene expression levels, explore the metabolic pathways involved in the responses of F. graminearum cells to acidic or alkaline conditions, and reveal how F. graminearum regulates intracellular metabolism and synthesis to adapt to the changes in extracellular pH. [Methods] F. graminearum was cultured in the PDB media with initial pH 4.5, 6.5, and 8.0 for 48 h, and the total RNA of the strains was extracted to construct the cDNA library. Transcriptome sequencing and bioinformatics analysis were used to identify the differentially expressed genes (DEGs), and the metabolic pathways involved were analyzed. The expression levels of target genes were determined by RT-qPCR. [Results] Under acidic conditions, a total of 4 283 DEGs were identified, including 2 032 genes with up-regulated expression and 2 251 genes with down-regulated expression. Under alkaline conditions, a total of 498 DEGs were identified, including 269 genes with up-regulated expression and 229 genes with down-regulated expression. Gene ontology (GO) enrichment analysis revealed 211 GO terms for the up-regulated genes and 72 GO terms for the down-regulated genes under acidic conditions. Under alkaline conditions, GO analysis yielded 33 GO terms for the up-regulated genes and 40 GO terms for the down-regulated genes. The results of Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis showed 22 up-regulated pathways and 32 down-regulated pathways under acidic conditions as well as 8 up-regulated pathways and 13 down-regulated pathways under alkaline conditions. The expression of the genes associated with membrane transporters and hydrolysis of carbohydrates was up-regulated, and that of the genes related to protein metabolism was down-regulated, which assisted F. graminearum cells to adapt to changes in the external environment. At the same time, F. graminearum maintained the internal environment balance by reducing secondary metabolism and amino acid metabolism under acidic and alkaline conditions, respectively, to resist extracellular pH stress. [Conclusion] In the acidic environment, F. graminearum adapts to the changes in the extracellular environment by promoting the production of ribonucleoprotein complexes and secondary metabolism. In an alkaline environment, F. graminearum senses and responds to external stresses via amino acid metabolism. The analysis of the metabolic pathways of F. graminearum cells provides gene expression data for studying the responses of F. graminearum to different pH environments. The findings of this study are helpful to understand the pathogenic mechanism of F. graminearum.