Acarbose, an α-glucosidase inhibitor, regulates the postprandial blood glucose level by competitively inhibiting the activities of sucrase, maltase, and glucamylase in the intestine, serving as an ideal drug ingredient with blood glucose-lowering activity. Acarbose is mainly produced by the fermentation of Actinoplanes sp., and its biosynthetic pathway is mainly divided into four modules: C₇-cyclitol synthesis, deoxyglucosamine synthesis, maltose integration, and extracellular transport of acarbose and its homologues (carbophore cycle). This paper reviewed the advances in the research fields mentioned above, aiming to provide ideas for further exploring the biosynthetic pathways of acarbose, catalytic mechanisms of related enzymes, and molecular modification of fermentation strains.

Microorganisms have survived and evolved in continuously changing and energy-limited environments for billions of years. Compared with those cultured in laboratories with abundant organic substrates, the microorganisms in natural oligotrophic environments exhibit significant differences in physiological states, gene expression, and protein synthesis. Under extreme and low-energy environmental stress, microorganisms utilize a range of substances such as hydrogen, ferrous ions, minerals, and organic remnants as energy or electron sources. They adjust their gene expression, metabolic pathways, and physiological states through various mechanisms to enhance energy utilization efficiency, adapt to nutrient-scarce conditions, sustain metabolic activities and population survival, and drive material transformation and element cycling. Understanding the physiological states of microorganisms in natural environments and their adaptive mechanisms to low-energy supply is crucial for revealing the microbial origins, evolution, growth, metabolism, dormancy, and the minimum energy requirements for life. This review introduces the formation, evolution, and distribution of natural low-energy environments (i.e., environments deficient in electron donors and carbon sources), as well as the physiological states and survival strategies of microorganisms in these variable low-energy environments. The research in this field advances microbial remediation technology development, extreme environment protection, and bio-mining technology development, representing a frontier in geomicrobiology.

[Objective] To study the effect of DNA damage response (DDR) on the replication of porcine epidemic diarrhea virus (PEDV). [Methods] Specific inhibitors were used to detect whether DDR pathway was involved in PEDV replication. The comet assay was employed to observe the DNA damage caused by PEDV infection in Vero cells. The changes in the expression levels of proteins in the DDR pathway and cell cycle of PEDV-infected Vero cells were determined by Western blotting and flow cytometry, respectively. [Results] The ATM inhibitor KU55933 significantly inhibited the replication of PEDV, with the virus titer decreasing from (5.50±0.25) log₁₀ TCID₅₀/mL to (3.15±0.15) log₁₀ TCID₅₀/mL. PEDV infection caused DNA damage in Vero cells during 12–60 h. ATM, ATR, Chk1, Chk2, and p53 were activated by PEDV infection of Vero cells. Especially, p-Chk2 and p-p53 showcased high expression during virus replication. In addition, PEDV infection led to the stagnation of Vero cells in the S phase. During virus replication, the expression of Cyclin B1 was first downregulated and then upregulated significantly. [Conclusion] PEDV perhaps utilized DNA damage pathway hijacks the ATM-Chk2 to manipulate the cell cycle and promote self-replication. The results provided a basis for elucidating the replication and infection mechanisms of PEDV and developing new potential antiviral targets.

Cyclic adenosine monophosphate (cAMP) is a second messenger widely present in eukaryotes. It is synthesized by adenylate cyclase (AC) and regulates downstream protein activity by binding to protein kinase A, thereby regulating fungal growth and development, virulence, cell wall integrity, environmental stress responses, and sexual/asexual reproduction. This article introduces the research progress of the cAMP signaling pathway in phytopathogenic fungi and the cooperation of this pathway with other signaling pathways in regulating cellular processes. At the same time, it elucidates the role of the cAMP signaling pathway in the infection of plant phytopathogenic fungi. This review is expected to provide reference for screening the agents for inhibiting phytopathogenic fungi that target the genes or proteins in the cAMP pathway. Additionally, the cAMP signaling pathway could be targeted to prevent and control the growth, development, and pathogenicity of phytopathogenic fungi in the future.

[Objective] Cold seeps and hydrothermal fields are typical chemosynthetic ecosystems in the ocean. With distinctive physicochemical properties, they harbor unique microbial communities. Dimethylsulfoniopropionate (DMSP), one of the most abundant organic sulfur-containing compounds on Earth, is synthesized and degraded by a variety of marine bacteria, which plays an important role in driving carbon and sulfur cycles in the ocean. In this study, we isolated and identified DMSP-synthesizing and degrading bacteria from the F-cold seep of the South China Sea and hydrothermal fields of the Okinawa Trough and analyzed their diversity and distribution, aiming to expand the understanding of these bacteria in the ocean. [Methods] Water, sediment, and animal samples were collected at different depths from both the F-cold seep of the South China Sea and the Yaeyama Knoll hydrothermal field of the Okinawa Trough. Three enrichment media (l-methionine addition and high salinity and low nitrogen for DMSP-synthesizing bacteria; DMSP addition for DMSP-degrading bacteria) and the 2216E medium were used for the enrichment and isolation of bacteria. The taxonomic status of strains was determined by 16S rRNA gene sequencing, and the abilities of representative strains to synthesize or degrade DMSP were assessed. [Results] A total of 874 culturable strains were obtained. Gammaproteobacteria emerged as the dominant class in the three media, and Marinobacter was the most abundant genus. The number and diversity of culturable strains obtained from cold seep samples after enrichment were higher than those from the hydrothermal field. The 14 strains of DMSP-synthesizing bacteria from the cold seep belonged to 7 genera, including 5 Thalassospira strains carrying the DMSP synthesis gene mmtN and 2 Pseudooceanicola strains carrying dsyB. A total of 130 DMSP-degrading bacterial strains were obtained from the cold seep, belonging to 39 genera, among which Glutamicibacter was the most abundant genus (24 strains) without known genes associated with DMSP degradation. There was only 1 strain of DMSP-synthetizing bacteria and 18 strains of DMSP-degrading bacteria from the hydrothermal field, both were much fewer than those from the cold seep. The strains with DMSP cleavage pathway accounted for 98.6% of the total DMSP-degrading strains (148), among which 55 strains had strong cleavage activity and were mainly Actinobacteria. Among the 40 strains with strong DMSP-degrading activity, 9 strains contained known cleavage genes and 3 strains contained known demethylation genes. [Conclusion] Abundant DMSP-synthesizing and -degrading bacteria exist in F-cold seep of the South China Sea and hydrothermal fields of the Okinawa Trough, including a variety of bacterial groups carrying potential novel DMSP synthesis/degradation genes. This study provides a basis for further understanding the microbial-driven organosulfur cycling in chemosynthetic ecosystems.

[Objective] Rivers and lakes are important and closely linked aquatic ecosystems, in which microorganisms are important organic components and participate in the transformation of various substances and energy flow. Comparing the bacterial and fungal communities and their co-occurrence networks between rivers and lakes is the key to a deeper understanding of the biogeochemical cycling in aquatic ecosystems of the Qaidam Basin. [Methods] We analyzed the diversity, structures, driving factors, and co-occurrence networks of bacterial and fungal communities in six rivers and four lakes of the Qaidam Basin by next-generation sequencing and statistical analysis methods. [Results] The abundance and diversity of bacteria and fungi in rivers were higher than those in lakes (Wilcoxon, P < 0.01). The most dominant bacterial phylum was Proteobacteria in both rivers and lakes (rivers: 6.0%–63.0%; lakes: 8.0%–61.0%), while the most dominant fungal phylum varied between rivers and lakes, being Ascomycota (0.5%–75.0%) in rivers and unclassified_k_Fungi (3.0%–87.0%) in lakes. The structures of bacterial and fungal communities differed between rivers and lakes (bacteria: R=0.599, P=0.001; fungi: R=0.435, P=0.001). Altitude (Alt), chlorophyll a (Chl-a), and total nitrogen (TN) were significant factors shaping bacterial community structures, while dissolved oxygen (DO), pH, and temperature (Temp) were significant drivers shaping fungal community structures in different aquatic ecosystems. The stability of bacterial and fungal communities varied significantly between habitats. Specifically, bacterial communities were more stable in rivers than in lakes, while fungal communities were more stable in lakes than in rivers. [Conclusion] The bacterial and fungal communities varied between rivers and lakes in the Qaidam Basin, demonstrating spatial heterogeneity. This study can provide data support for the in-depth study of the differences and connections of the microbial community characteristics between rivers and lakes in the Qaidam Basin. Moreover, it lays a theoretical foundation for the protection and management of water resources in this region.

[Objective] To study the plant disease-inhibiting and growth-promoting effects and identify the antimicrobial components of Streptomyces levis L2. [Methods] Morphological features and the phylogenetic tree based on the 16S rRNA gene sequences were employed to identify the strain L2 isolated from the rhizosphere of drought-tolerant Echinochloa crusgalli. The antimicrobial components produced by the strain were identified by chromatography and high-resolution mass spectrometry. The whole genome of the strain was sequenced by Illumina in combination with Nanopore. antiSMASH was employed to search for the biosynthetic gene clusters. [Results] Streptomyces levis L2 and its fermentation broth inhibited the growth of Gram-positive bacteria and phytopathogenic fungi, and the strain produced a large transparent zone on the CAS (chrome azurol sulphonate) plate and could produce indole-3-acetic acid (IAA). The antimicrobial components of the strain showed the m/z of 537.102 0 [M+H]⁺ (calcd for C₂₇H₂₀O₁₂, 537.103 5, 2.2×10^–6) and 523.086 3 [M+H]⁺ (calcd for C₂₆H₁₈O₁₂, 523.087 8, 2.9×10^–6), which were consistent with the exact masses of α-rubromycins, β-rubromycins and γ-rubromycins, with the errors less than parts per 5 million. Their HPLC retention time were in agreement with that of standard rubromycins. The whole genome of L2 had a length of 8.8 Mb and carried 32 biosynthetic gene clusters for secondary metabolites including rubromycins. [Conclusion] S. levis L2 exhibited excellent plant disease-inhibiting and growth-promoting properties, thus could be further developed as biocontrol agents. It produces the antimicrobial components rubromycins and its biosynthetic gene clusters contained 6 more modification genes than the previously published gene clusters for rubromycins and several genes with unknown functions.

Vitamin B₁₂ (VB₁₂) is an essential nutrient and growth cofactor for the majority of organisms. It exerts influence not only on the structure of microbial communities and marine primary productivity but also on the global biogeochemical cycles, thus justifying its designation as a "hard currency" in marine ecosystems. Ammonia-oxidizing archaea (AOA), initially isolated from the ocean in 2005, are distinguished by their chemolithoautotrophic characteristics. Genomic, metabolomic, and culture studies have demonstrated that AOA are among the few microbial groups capable of synthesizing VB₁₂ in the ocean. This capability is crucial for maintaining microbial community stability and biogeochemical functions. This review summarizes the measurement methods and distribution characteristics of VB₁₂ in the ocean and the pathways through which AOA produce VB₁₂. It discusses the importance of AOA in marine VB₁₂ supply and outlines the future research directions for VB₁₂ production by AOA.

[Objective] To study the therapeutic effect of Bifidobacterium adolescentis strains with strong antioxidant capacity on a mouse model of ulcerative colitis (UC). [Methods] The B. adolescentis strains with strong antioxidant capacity were screened based on 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging rate, reducing capacity, and hydrogen peroxide tolerance. Subsequently, we established a mouse model of dextran sulfate sodium (DSS)-induced colitis to investigate the alleviating effects of the B. adolescentis strains with strong antioxidant capacity on UC. [Results] Among the 26 strains of B. adolescentis, TH02767, TH03658, and TH03664 demonstrated strong antioxidant capacity. Only TH02767 showed an alleviating effect on UC in terms of disease activity index and spleen index in the mouse model (P < 0.05). Moreover, the intervention with TH02767 lowered the levels of tumor necrosis factor-α, interleukin-6, interleukin-1β, and myeloperoxidase (P < 0.05), while enhancing the production of interleukin-10 (P < 0.05) in the colon. In addition, TH02767 modulated gut microbiota in the mice by reducing the relative abundance of Deferribacterota and increasing the relative abundance of Bacteroidetes. At the genus level, it increased the relative abundance of Muribaculum and Muribaculaceae (P < 0.05). [Conclusion] B. adolescentis TH02767 screened out in this study for its robust antioxidant capacity not only ameliorates the clinical symptoms associated with DSS-induced colitis in mice but also significantly reduces the levels of pro-inflammatory cytokines and modulates the gut microbiota.

[Objective] To explore the effects of rice-crab co-culture on physicochemical indicators and microbial community structure of soil in the Yellow River irrigation area of Ningxia and thus provide a theoretical basis for promoting rice-crab farming in the Yellow River irrigation area in northwest China. [Methods] The physicochemical indicators of soil were measured, and high-throughput sequencing of 16S rRNA gene amplicons was employed to reveal the microbial community structure in the fields with only rice planting (CK) and rice-crab co-culture (EG) by introduction of crabs into the ditches around rice plots. [Results] EG had higher soil pH, total nitrogen (TN), and soil organic matter (SOM) and lower total salt content than CK from April to August. The TN, available phosphorus (AP), and SOM in EG were significantly higher than those in CK in June and July. In terms of microbial community structure characteristics, EG significantly altered the bacterial community structure in soil, increasing the bacterial diversity and abundance in April, and August. EG had higher cumulative relative abundance of the top 20 bacterial phyla than CK from April to August. The dominant phylum of both CK and EG from April to August was Proteobacteria. At the genus level, EG increased the relative abundance of Pseudomonas and decreased the relative abundance of Thiobacillus and Methanosaeta. The comparison showed that EG had stronger effect on the bacterial community structure than the sampling month. Correlation analysis shows that TN is the main factor affecting the relative abundance of soil bacteria, and it is significant (P < 0.05). [Conclusion] Compared with traditional rice monoculture (CK), sampling rice crab intercropping (EG) enhances soil fertility, increases the relative abundance of Proteobacteria and Pseudomonas in the soil, and helps improve soil fertility and nutrient cycling efficiency, as well as clean up pollutants in soil and water bodies.