Microbial deodorization is an effective technology for treating odorous waste gases, in which microbial strains play a decisive role. [Objective] To screen the strains capable of degrading dimethyl disulfide (DMDS) and investigate their degradation efficiency and ability to produce surfactants under various conditions. [Methods] DMDS, a typical sulfur-containing odorous organic compound, was selected as the sole carbon source. A strain R1 capable of simultaneously producing biosurfactants and degrading DMDS was isolated from mangrove sludge. The strain was identified based on the physiological and biochemical characteristics analysis and 16S rRNA gene sequencing. The types of self-produced biosurfactants were determined using infrared spectroscopy and nuclear magnetic resonance spectroscopy analysis. [Results] Based on physiological and biochemical characteristics and 16S rRNA gene sequence, strain R1 was identified as Achromobacter sp. The strain was capable of degrading DMDS, with optimal degradation conditions of an initial DMDS concentration of 12.49 mg/L, a system temperature of 30 ℃, and an inoculum amount of 1.0 g/L, under which the DMDS degradation rate reached 70.74%. Emulsification experiments showed that strain R1 can use DMDS as a carbon source to produce biosurfactants, which were identified as glycolipids through nuclear magnetic resonance and infrared spectroscopy. [Conclusion] The main intermediate product in the biodegradation of DMDS is methyl mercaptan, and the transformation rate of sulfur to SO₄^2- is 65.99%. Strain R1 exhibits impressive performance in degrading DMDS and producing biosurfactants.

[Objective] To systematically investigate the substrate promiscuity and catalytic performance of three UDP-glycosyltransferases: CsUGT75L12 (Camellia sinensis), CiUGT11 (Chrysanthemum indicum), and UGT73B1 (Arabidopsis thaliana). [Methods] The recombinant proteins of plant glycosyltransferases were heterologously expressed in Escherichia coli BL21(DE3) and purified for in vitro enzymatic assays. In vitro enzymatic reactions of the purified recombinant proteins were performed with six flavonoids including flavones (apigenin and acacetin) and flavanones (naringenin, eriodictyol, isosakuranetin, and hesperetin). The enzymatic products were characterized by HPLC and LC-MS and the conversion rates were calculated through comparative HPLC peak area analysis. [Results] CsUGT75L12, CiUGT11, and UGT73B1 exhibited broad substrate promiscuity towards the six tested flavonoids. The primary products were identified as flavonoid-7-O-glucosides. Notably, CiUGT11 and UGT73B1 demonstrated exceptional catalytic efficiency, achieving >96% conversion rates for hesperetin and naringenin. Leveraging this activity, we engineered CiUGT11 and UGT73B1 with high efficiency to produce hesperetin-7-O-glucoside and naringenin-7-O-glucoside through precursor feeding in E. coli. [Conclusion] The three glycosyltransferases display remarkable versatility in flavonoid recognition, with conserved preference for the C7-OH position. CiUGT11 and UGT73B1 show high catalytic efficiency for six flavonoids. These findings provide candidate gene elements for the efficient microbial production of flavonoid glycosides.

[Objective] To clarify phyllosphere microbial responses to the invasion of areca palm velarivirus 1 (APV1), a virus causing yellow leaf disease of areca (Areca catechu), and provide a theoretical basis and technical support for the study of phyllosphere micro-ecology, exploration of excellent biocontrol resources, and green prevention and control of yellow leaf disease of areca. [Methods] We collected healthy leaves, mildly diseased leaves, and severely diseased leaves of areca. The phyllosphere microbial community structure and diversity were compared by high-throughput sequencing and bioinformatics methods. Furthermore, functional differences of phyllosphere microbial communities were analyzed. [Results] The dominant bacterial phyla in the phyllosphere of areca included Actinobacteriota, Proteobacteria, Acidobacteriota, Firmicutes, and Myxococcota, while the dominant fungal phyla were Ascomycota and Basidiomycota. As the disease became increasingly severe, bacterial richness initially increased then decreased while fungal richness initially decreased then increased. However, both bacterial diversity and fungal diversity showed a trend of first increasing and then decreasing. Firmicutes and Basidiomycota served as indicators of mildly diseased areca, with the relative abundance showing consistent trends with alpha diversity. The healthy plants and the diseased plants showed different phyllosphere microbial functions. Specifically, the environmental information processing function was significantly higher in severely diseased areca plants than in healthy ones. Additionally, the relative abundance of symbiotroph fungi in the phyllosphere were significantly higher in severely diseased areca plants than in healthy ones. [Conclusion] The yellow leaf disease significantly alters the phyllosphere microbial community structure and diversity of areca, with greater changes during the early disease stage. This suggests that areca may defend against APV1 infection by recruiting beneficial microorganisms, regulating cellular metabolism and biochemical reactions, and activating autoimmunity.

[Objective] The conversion of upland to paddy fields and increased fertilizer application have significantly altered soil properties. However, the dynamic evolutionary characteristics and response mechanisms of microbial communities during habitat evolution different years after conversion remain unclear. [Methods] Soil samples were collected from the paddy fields converted from upland fields for different years (0, 3, 8, 15, 20, and 30). Soil physicochemical analysis, real-time quantitative PCR, and high-throughput sequencing were employed to investigate the dynamic changes in soil chemical and biological properties, microbial community composition and asynchrony characteristics, and the interrelationships among these indicators during the habitat evolution following conversion. [Results] As the years after conversion increased, soil organic carbon, total nitrogen, total phosphorus, ammonium nitrogen, and microbial biomass carbon content gradually increased (by 3 to 4 folds), while pH (decreased by up to 0.80) and nitrate content gradually decreased. However, soil potassium content, microbial abundance, and microbial diversity showed no consistent trends. Microbial community analysis revealed that as the years after conversion increased, stress-tolerant genera (Balneola, Flavobacterium, Myxococcus, and Nitrospira) presented enhanced asynchrony and divergence. This optimized interspecies interactions and functional division, thereby improving ecosystem stability. Conversely, increased convergence in genera such as Liberibacter and Variovorax weakened soil functions such as plant growth promotion and pathogen suppression. Correlation analysis indicated that soil pH, organic carbon, and total nitrogen acted as key environmental drivers. Through synergistic and antagonistic interactions, they governed microbial community succession and exerted decisive influences on changes in community asynchrony. [Conclusion] As the years after upland-to-paddy conversion increased, the microbial community asynchrony became enhanced, which improved system stability and reduced carbon losses while compromising soil capacities of plant growth promotion and disease suppression. In the future, strategies such as water management, organic amendment regulation, precision fertilization, and application of synthetic microbial consortia could be employed to directionally enhance microbial divergence and improve ecosystem functional stability.

[Objective] Transcription is the first step in gene expression, and the mRNA abundance to a certain extent determines the final protein expression abundance. Recent studies have found that different ribosome-binding sites (RBSs) located in the 5′ untranslated region (5′-UTR) can affect the mRNA abundance of the downstream gene. From the perspective of regulatory factors in the mRNA degradation process, the effect may be attributed to the binding strength between the Shine-Dalgarno (SD) sequence and the ribosome and the local secondary structure of the 5′-UTR. [Methods] We constructed a 5′-UTR mutant library with a size of 528. High-throughput sequencing was employed to efficiently collect the information on the mRNA abundance of downstream egfp corresponding to various 5′-UTR variants. The effectiveness was verified by RT-qPCR. [Results] The association between abundance of each mRNA mutant and its corresponding 5′-UTR sequence was analyzed. The results showed that the SD sequence with moderate to strong binding strength to the ribosome was most conducive to maintaining high mRNA abundance. Too high or low binding strength will lead to a reduction in the mRNA abundance. The completely conserved core SD sequence (GGAGG) was the key to ensuring high binding strength, and the decline in conservation would cause a significant decrease in the mRNA abundance. When the SD sequence was similar among different 5′-UTR variants, i.e.,the binding strength of the SD sequence to the ribosome was comparable, the local secondary structure of the 5′-UTR was instable and the abundance of corresponding mRNA was high. [Conclusion] This study delves into the regulatory effects of 5′-UTR sequence features 5′-UTR on the mRNA abundance and establishes a qualitative model of their interrelationships, providing a reference for the rational design of regulatory elements in metabolic engineering and gene circuits.

Streptomyces can produce various active secondary metabolites, which can be widely used in medical, industrial, agricultural, and other fields. The secondary metabolite synthesis in Streptomyces is regulated by pathway-specific, pleiotropic, and global regulatory genes. The two-component system, as the main signal transduction system in prokaryotes, participates in various physiological and biochemical reactions of Streptomyces and can globally regulate secondary metabolites. The deletion or overexpression of specific two-component system genes can significantly affect the biosynthesis of secondary metabolites. Identifying the functions of two-component systems and elucidating their regulatory mechanisms can contribute to enhancing the production efficiency of secondary metabolites by genetic engineering. This paper reviews the research trends of two-component systems in various Streptomyces species such as Streptomyces albidoflavus in recent years and particularly summarizes and elaborates on the regulatory mechanisms of their secondary metabolite synthesis.

[Objective] To screening stress-tolerant and high-yielding rhizobia with growth-promoting effects on Sesbaniacannabina and provide rhizobia resources for efficient cultivation of S. cannabina in saline-alkali soil. [Methods] The culture method was used to isolate endophytic rhizobia from S. cannabina ‘Zhongkejing 1’. Based on 16S rRNA gene and whole genome sequencing, the strains were identified, and their stress tolerance and plant growth-promoting characteristics were evaluated. Their growth-promoting effects on the original host variety and other materials of S. cannabina were verified. [Results] The rhizobia isolated from the root nodule samples of S. cannabina ‘Zhongkejing 1’ were identified as a species belonging to Rhizobium. Based on the ANI and dDDH values of the whole genome sequence, the strain was identified as a new species of Rhizobium and named Rhizobium sesbaniae ZK1^T. R. sesbaniae ZK1^T can tolerate a NaCl concentration of 2.0% and survive within the range of pH 4.0-10.0, and it had the ability to dissolve organophosphorus compounds. Pot experiments were conducted to evaluate the effects of R. sesbaniae ZK1^T on the growth and nodulation of different materials of S. cannabina. The results revealed that R. sesbaniae ZK1^T promoted the growth and nodulation of these materials, while it had a more efficient symbiotic relationship with the host variety. [Conclusion] The isolated new species R. sesbaniae ZK1^T plays a role in promoting the growth and nodulation of S. cannabina and can tolerate severe acid, alkali, and salt stress. The findings have important theoretical significance and a practical value for the efficient improvement of plant-microorganism interactions in marginal land.

Saline-alkali stress is one of the main abiotic constraints limiting plant growth and development. Endophytic bacteria can enhance the stress tolerance of host plants by increasing osmotic adjustment substances and boosting antioxidant enzyme activities. [Objective] To isolate and identify saline-alkali tolerant endophytic bacteria from the roots of alfalfa grown in saline-alkali soil and evaluate them regarding the saline-alkali tolerance, plant growth-promoting traits, effects on alfalfa growth under saline-alkali stress, and colonization. [Methods] Saline-alkali tolerant endophytes were isolated by the tissue homogenization method from alfalfa roots. Strains were identified by morphological observation, 16S rRNA gene-based phylogenetic analysis, and physiological and biochemical assays. Multiple plant growth-promoting traits were assayed in vitro. A greenhouse pot experiment was conducted to assess the effect of the selected strain on alfalfa growth under saline-alkali conditions. Colonization of strain Z-1 in alfalfa roots was visualized by green fluorescent protein tagging and laser scanning confocal microscopy. [Results] Pseudomonas moraviensis Z-1 was successfully isolated from the roots of alfalfa growing in saline-alkali soil. The endophytic bacterial strain tolerated 4% NaCl and pH 9.0 and displayed the ability to produce 1-aminocyclopropane-l-carboxylate deaminase, siderophores, indole-3-acetic acid, and soluble phosphorus. Under saline-alkali conditions, inoculation with Z-1 significantly increased the dry weights of the aboveground parts, root vigor, and soluble protein content of alfalfa. Moreover, the strain significantly increased catalase, peroxidase, and superoxide dismutase activities and decreased the hydrogen peroxide, superoxide anion, and malondialdehyde content (P<0.05). Confocal microscopy confirmed successful colonization of Z-1 in alfalfa roots at 7.57×10⁴ CFU/g. [Conclusion] The saline-alkali tolerant endophytic bacterium Z-1 plays a vital role in promoting alfalfa growth and enhancing its tolerance to saline-alkali stress. It represents a promising candidate for developing microbial preparations to ameliorate saline-alkali soil.

[Objective] Both no-tillage with straw mulching and combined application of organic and inorganic fertilizers can effectively enhance soil fertility. However, the mechanisms by which they influence microbial carbon and nitrogen turnover remain unclear. [Methods] Soil samples included conventional tillage (CK) as the control, along with two management treatments: soils under combined application of organic and inorganic fertilizers (CM) and no-tillage with straw mulching (CT). By employing DNA-stable isotope probing (DNA-SIP) with ¹³C-glucose in a laboratory microcosm incubation experiment, we investigated the responses of microbial activities in black soil to exogenous glucose and urea addition. Key processes examined included respiration, mineralization, dissimilatory decomposition (measured by ¹³C-CO₂), assimilatory formation of stable organic carbon (measured by ¹³C-SOC), priming effects, N₂O emissions, carbon neutrality, and active microorganisms. [Results] In the control treatment with water addition, soil microbial respiration and mineralization intensity followed the order of CK<CM<CT, which showed the maximum CO₂ emission rates of 0.413, 0.589, and 0.615 µmol/(g⋅d), respectively. Exogenous carbon and nitrogen addition induced positive priming effect, with the intensity ranking as simultaneous carbon and nitrogen addition (Glu+N)>carbon-only addition (Glu)>nitrogen-only addition (N). However, the priming effect did not continuously enhance with the increase in the total amount of exogenous organic matter. Dissimilatory decomposition enhanced as the amount of exogenous addition increased, with cumulative ¹³C-CO₂ emissions following the trend of CK (97.0 nmol/g)>CM (90.4 nmol/g)>CT (81.9 nmol/g). The content of stable ¹³C-SOC produced by microbial assimilation in CT was 296.4 nmol/g, higher than that in CM (263.5 nmol/g). The carbon use efficiency of soil in the three groups was approximately 80%, and about 30% of N₂O emissions were offset by the formation of ¹³C-SOC. Carbon neutrality analysis revealed that the net CO₂ emissions from CK and CT soil samples were 50% higher than those from the CM soil sample. Additionally, under the addition of exogenous carbon and nitrogen, the active ammonia-oxidizing microorganisms during microbial proliferation were primarily ammonia-oxidizing bacteria, specifically Nitrosospira. [Conclusion] CT demonstrates higher respiration, mineralization, and carbon sequestration capabilities and lower dissimilatory decomposition capability in enhancing soil fertility than CM, while it results in higher net CO₂ emissions.