Abstract:Microalgae are rich in lipids, starch and other high-value metabolites that can be used in the production of food, feed, chemicals, and energy. However, the trade-off between the growth and product accumulation of microalgae in large-scale culture restricts the commercial application of microalgae. The two-stage culture of microalgae can overcome this problem by separating cell growth from product accumulation. It is one of the key means to promote the commercialization of microalgae, with high productivity, low energy consumption, emission reduction, and a wide application range. This review summarizes the advantages and product types of the existing two-stage culture technology of microalgae, analyzes the limiting factors, and discusses the prospects for the future of this technology. Moreover, this paper points out that the unclear stage transition time and high cost of intermediate harvesting are two bottlenecks that limit the application of this technology. This review provides a theoretical foundation and technical means for the decision-making and implementation of a large-scale production plan for the two-stage culture of microalgae in the future.

Abstract:As the economic level and living standards are rising, the incidence of type 2 diabetes mellitus (T2DM), a nutritional metabolic disease caused by overnutrition, has increased sharply. The elevated blood glucose level and complications seriously affect the quality of life of the patients and bring economic burden to the family. The drug treatment of T2DM has limitations and side effects. Although T2DM is difficult to be cured, some new therapies for regulating blood glucose have emerged with the deepening of research. Probiotics are safe, economical, and effective, and recent studies have shown that probiotics used alone or in combination with other therapies can lower blood glucose level and alleviate complications. Demonstrating a promising application prospect in the prevention and treatment of T2DM and the remodeling of intestinal microbiota, probiotics have become a hot research spot. While probiotics have the potential to overcome T2DM, the mechanism of probiotics in regulating blood glucose remain to be deciphered. This article reviews the role, application, prospect, and challenges of probiotics in blood glucose regulation, aiming to provide a theoretical basis for the development of microecological agents for blood glucose regulation in humans and companion animals.

Abstract:Wastewater treatment plants (WWTPs) are the major sources and sinks of antibiotic resistance genes (ARGs) and antibiotic resistance bacteria (ARB), and bioaerosols are the key carriers for the emissions of ARGs and ARB from WWTPs to the surrounding environment. The systemic review about the pollution characteristics, sources, and potential risks of the antibiotic resistance of bioaerosols from WWTPs remains to be carried out. We reviewed the research status of antibiotic resistance pollution in bioaerosols from WWTPs from the perspectives of sampling and detection methods, escape characteristics, sources, and potential hazard and risk assessment. Inertial sampling and filtration were the commonly used methods for collecting antibiotic resistant bioaerosols from WWTPs. Metagenomic sequencing, assembly, and binning can probe into the composition, mobility, and hosts of ARGs. The ARGs conferring resistance to multidrug, bacitracin, aminoglycoside, tetracycline, beta-lactam, sulfonamide, macrolide-lincosamide-streptogramin, and glycopeptide were widely detected in PM₁₀, PM_2.5, and PM_1.0 from WWTPs. The main emission units of ARGs and ARB loaded by PM₁₀, PM_2.5, and PM_1.0 from WWTPs were screen rooms, biochemical reaction tanks, and sludge treatment units. The existence of pathogenic ARB in size-segregated bioaerosols from WWTPs increased the difficulty of antibiotic treatment, and sewage and sludge contributed to the release of ARGs and ARB. Furthermore, relevant prospects were proposed in terms of research content, research technology, and control strategies, so as to provide references for monitoring and protecting against bioaerosol antibiotic resistance pollution in WWTPs.

Abstract:Fusarium wilt is a refractory soil-borne disease known as "cancer" in cucurbitaceous vegetables. It has become a bottleneck restricting the sustainable development of the cucurbitaceous vegetable industry in China. We briefed the negative impacts of Fusarium wilt on cucurbitaceous vegetables and introduced the damaging mechanism of Fusarium wilt from cell wall-degrading enzymes, toxins, signal transduction, and virulence genes. Furthermore, we innovatively elaborated on the mechanism by which rhizosphere microbiome in defending against Fusarium wilt of cucurbitaceous vegetables from the pathogen, soil, and plant perspectives. We then discussed the key factors associated with the occurrence and inhibition of Fusarium wilt. Finally, we prospected the construction of the core microbiome and the research on the molecular mechanism of rhizosphere microbiome. It is expected that the application of biocontrol microorganisms in the prevention and control of diseases will enter a new era. This work can provide ideas for deciphering the mechanism of improving crop resistance to diseases.

Abstract:The discovery of heterotrophic nitrifying-aerobic denitrifying (HN-AD) bacteria updates the conventional theory of nitrifying. The HN-AD bacteria capable of simultaneous nitrification and denitrification under aerobic conditions have become a research hotspot in recent years. These bacteria play a key role in the marine nitrogen cycle. We introduced the diversity, nitrogen metabolic pathways, and related enzymes of marine HN-AD bacteria and analyzed the effects of environmental factors (salinity, C/N ratio, dissolved oxygen, pH, etc.) on the denitrifying performance of HN-AD bacteria. Furthermore, we summarized the functioning processes and applications of these bacteria and made an outlook on the development directions of this field.

Abstract:[Background] Nocardioides sp. InS609-2 is a potential new strain of polar actinomycete isolated from the soil sample collected from Inexpressible Island in Terra Nova Bay of the Ross Sea, Antarctica. Little is known about the full genome sequence, functional genes, metabolite synthesis pathways, and comparative genomics of Nocardioides sp. InS609-2. [Objective] To explore the genes associated with secondary metabolites from the genome sequence of Nocardioides sp. InS609-2. [Methods] The complete genome map of InS609-2 was sequenced on the Illumina HiSeq platform, followed by read assembly, gene prediction, gene annotation, prediction of gene clusters for secondary metabolite biosynthesis, and synteny analysis. [Results] The full length of the genome was 4 524 052 bp, with the G+C content of 69.42%. A total of 4 656 genes, 56 tRNAs, and 6 rRNAs were predicted. Among them, 3 761, 3 052, 1 767, 4 134, and 2 725 genes were annotated in COG, GO, KEGG, NR, and Swiss-Prot, respectively. Meanwhile, 19 gene clusters for secondary metabolite synthesis were predicted. Genome sequencing data was submitted to NCBI, with the GenBank accession number CP060034. The synteny analysis and protein cluster analysis were performed for Nocardioides sp. InS609-2 together with N. dokdonensis CP015079, N. yefusunii CP034929, N. euryhalodurans CP038267, N. seonyuensis CP038436, N. daphniae CP038462, and N. okcheonensis CP087710. The results showed both conserved and unique regions among the seven genomes. The seven genomes shared 44 protein clusters. Finally, the 16S rRNA gene-based phylogenetic analysis, pan genome analysis, core genome analysis, and genome-based phylogenetic analysis were carried out to further mine the genomic information of Nocardioides sp. InS609-2. [Conclusion] This study provides reference information for predicting the gene clusters involved in secondary metabolite biosynthesis of Nocardioides sp. InS609-2 at the genomic level, which is essential for the subsequent studies of InS609-2.

Abstract:[Background] The contamination of arsenic (As), a highly toxic metalloid, in water is aggravating, which threatens human health. The common method used for removing As is adsorption, and it is urgent to develop efficient As removal methods. [Objective] To characterize an iron-oxidizing bacterial strain FX8 isolated from the surface soil of iron ore, so as to use the iron mineral (adsorbent) produced by the strain via oxidizing Fe(II) for removing As. [Methods] The strain was identified based on morphological, physiological, and biochemical characteristics and genome-wide sequencing evidence. The concentrations of total Fe and Fe(II) were determined by phenanthroline spectrophotometry. The iron oxide precipitates were analyzed by X-ray diffraction, X-ray photoelectron spectroscopy, and energy dispersive spectrometer. The concentration of total As was determined by high performance liquid chromatography in combination with hydride generation and atomic fluorescence spectroscopy. [Results] Strain FX8 was Gram-positive and aerobic, with while and round colonies. Its cells were rod-shaped with the size of (0.5-2.5) μm×(0.13-0.25)μm. FX8 was identified as a strain of Arthrobacter. It could oxidize Fe(II) to generate iron oxide precipitates which were an amorphous Fe(III) mineral with poor crystallinity and a large amount of biological impurities. Strain FX8 oxidized Fe(II) by producing extracellular enzymes. The strain cultured with As(III) or As(V) at 28℃ and 150 r/min showed the total Fe removal rates of 100% in 48 h and the corresponding total As removal rates of 99.54% and 99.86%, respectively. When the extracellular enzyme liquid of strain FX8 was added into the As(III) or As(V) system, the total Fe removal rates reached 100% in 2 h, and the corresponding total As removal rates were 99.45% and 100%, respectively. [Conclusion] Strain FX8 is an iron-oxidizing bacterium, and the iron biomineralization with its extracellular enzyme liquid outperforms strain-arsenic coculture in the removal of As. The findings provide new biomaterials and theoretical references for the efficient remediation of As-contaminated water.

Abstract:[Background] Salt marshes in desert steppe are an important part of terrestrial ecosystems, and soil moisture and salinity changes are important factors affecting the soil bacterial community assembly in this ecosystem. [Objective] The soil bacterial community assembly is a continuous ecological process dominated by deterministic and stochastic processes. Revealing the assembly mechanism of soil bacterial communities in salt marshes of desert steppe helps to deepen our understanding about the importance of microorganisms as key ecosystem factors. [Methods] The physicochemical properties were measured for the soil samples collected near the Kushuihu lake (NL) and far from the Kushuihu lake (FL), a typical salt marsh area of the desert steppe in central Ningxia. High-throughput sequencing was performed to analyze the bacterial information. [Results] NL and FL sampling sites presented significant water-salt gradients. The NL soil samples had higher pH, water content, and electrical conductivity than the FL soil samples. Proteobacteria, Actinobacteriota, Firmicutes, Bacteroidota, and Myxococcota were the dominant phyla in the soil samples. As the water-salt gradient increased, the relative abundance of Proteobacteria increased, while that of Actinobacteriota and Firmicutes decreased. Most of the members belong to the phyla had obvious correlations with water-salt changes. In addition, the soil bacterial network in the FL sites had stable network relationship. From the NL to FL sampling sites, the soil bacterial community gradually became being dominated by stochastic factors and was influenced by soil pH, electrical conductivity, and environmental variables. [Conclusion] The changes in soil moisture and salinity in salt marshes of desert steppe altered the soil bacterial community structure. Soil bacterial communities improved the survival under stress by strategies such as niche occupation. The assembly of bacterial communities is a continuum consisting of stochastic and deterministic processes, which are influenced by environmental changes. The results reveal the response characteristics of bacterial community structure and interrelationship to environmental changes in salt marshes of desert steppe and clarify the assembly mechanism and influencing factors of soil bacterial community, providing a theoretical reference for related studies.

Abstract:[Background] Qinghai harbors rich wild Morchella resources, whereas studies remain to be carried out for the species identification and characterization. [Objective] To identify a wild Morchella strain collected from Qilian, Qinghai and analyze its biogeography. [Methods] The morphological characteristics were combined with genealogical concordance phylogenetic species recognition and the phylogenetic analyses to identify the Morchella strain. Furthermore, species divergence time was analyzed and the geographic ancestral region was rebuilt. [Results] The strain MQL-1 presented a yellow-brown domed cap and a white hollow stalk, with a spore size of (21.17±4.33) μm×(14.26±3.25) μm and a hyphal diameter of (13.95±3.19) μm. Strain MQL-1 had 99% ITS sequence identity with Esculenta clade of the genus Morchella, and the genealogical concordance phylogenetic species recognition identified MQL-1 as Morchella crassipes. The estimated divergence time and reconstructed geographic ancestral region indicated that M. crassipes MQL-1 diverged from M. crassipes M10 at approximately 12.75 Mya (million years ago), and its most likely reconstructed geographic ancestral region was India (52.49%). [Conclusion] We isolated and identified a wild Morchella strain in Qinghai. This study enriched the information database of Morchella resources in Qinghai, laid a foundation for the follow-up work, and provided new ideas for fungal research.

Abstract:[Background] Bacterial fruit blotch caused by Acidovorax citrulli is a prevalent disease in cucurbitaceous crops, and the type III effectors (T3Es) secreted by the type III system into plants are the major pathogenic factors of A. citrulli. However, the knowledge about the T3Es in A. citrulli is limited. [Objective] To identify a novel T3E, Acidovorax outer protein AI (AopAI), in A. citrulli, and investigate its impact on the bacterial pathogenicity and interference with plant immunity. [Methods] Bioinformatics tools were used to analyze the sequence characteristics of AopAI, and then the AvrBs1 as an avirulent reporter was used to verify the transport function of AopAI. Fluorescence quantitative polymerase chain reaction (PCR) was carried out to determine the expression of aopAI and the effect of AopAI on the expression of marker genes of the PAMP-triggered immunity (PTI) signaling pathway in plants. Furthermore, the gene insertion mutation and functional complementation methods were employed to examine the pathogenicity of the pathogen and the accumulation of hydrogen peroxide and callose in plants. Finally, the transient expression method was used to predict the subcellular localization and the ability of AopAI to inhibit elicitor-induced cell death. [Results] AopAI had a conserved domain of adenosine diphosphate (ADP) ribosyltransferase and no transmembrane helix region or signal peptide. The expression of aopAI was significantly down-regulated in the mutants of hrpX and hrpG (core regulatory genes of T3SS). The co-expression of aopAI and the AvrBs1 functional region (59-445 aa) induced the hypersensitive reaction in the leaves of 'ECW-10R' pepper, which indicated that AopAI was a transporter protein. The aopAI mutant presented declined pathogenicity to cucumber cotyledons, while it increased the accumulation of hydrogen peroxide and callose. After transient expression of AopAI in Nicotiana benthamiana, the protein was localized in the cell membrane and nucleus. Additionally, AopAI inhibited the elicitor NIP-induced leaf cell death and down-regulated the expression of the PTI marker genes GRAS2 and ACRE31. [Conclusion] We identified a typical T3E, AopAI in A. citrulli, which was localized in the nucleus and cell membrane and had an ADP ribosyltransferase domain. AopAI functioned as a virulent protein inhibiting NIP-induced cell death and reduced hydrogen peroxide and callose by inhibiting the ACRE31-regulated immune pathway, thus suppressing the PTI defense mechanism in plants.

Abstract:[Background] Soil-borne diseases are a key factor limiting the agriculture sustainable development in the world and become increasingly serious in vegetables and Chinese medicinal herbs in China, leading to critically continuous-cropping obstacles. Biocontrol of soil-borne diseases, without causing safety problems to the environment and agricultural products, is a hot research topic. [Objective] To identify the strain JJYY with a broad antimicrobial spectrum to soil-borne pathogens, evaluate its control effects on major soil-borne diseases, and identify its major antimicrobial metabolic products. [Methods] This strain was identified by a combination of morphological observation with scanning electron microscopy, physiological and biochemical tests, and 16S rRNA gene sequencing. Turbidimetry and mycelial growth inhibition assay were employed to determine the EC₅₀ of this strain against four soil-borne bacterial pathogens and five fungal pathogens, respectively. Pot experiments were carried out to evaluate the control effects of the strain on tomato bacterial wilt and other diseases. Illumina NovaSeq and PacBio Sequel were used for whole genome sequencing of this strain, followed by functional annotation in PGAP. Preparative reversed-phase liquid chromatography (prep-RPLC) and mass spectrometry (MS) were employed to isolate and identify the metabolites of this strain. [Results] The strain JJYY was identified as Bacillus velezensis. The EC₅₀ values of the extract of this strain against four soil-borne bacterial pathogens and five soil-borne fungal pathogens were 0.940-1.092 mg/mL and 2.733-3.678 mg/mL, respectively. The strain showed the highest control effects of 80.00%-87.74% on tomato bacterial wilt, Chrysanthemum morifolium root rot, and capsicum Fusarium wilt, with no significant difference compared with streptomycin or hymexazol (P>0.05). The whole genome of this strain was 3 929 792 bp in length, carrying 3 895 genes. The genome of this strain shared 3 445 and 2 997 homologous genes with B. velezensis JS25R and B. subtilis 168, respectively. Twelve gene clusters were predicted to be associated with the synthesis of secondary metabolites. A total of 9 antimicrobial components were separated from the extract of this strain, of which two were preliminarily identified as macroactin D and 7-O-malonyl-macroactin A. [Conclusion] B. velezensis JJYY demonstrates definite control effects on both soil-borne bacterial and fungal diseases, with the genome distinct from reported B. velezensis strains. It produces diverse known and possible novel antibiotics. Identifying the antimicrobial substances and deciphering the antimicrobial mechanisms of this strain would facilitate the development of novel effective biocontrol agents.

Abstract:[Background] Lactic acid bacteria (LAB) and Bacillus are commonly used probiotics in production, with different growth characteristics. It is essential to understand the biological characteristics of different strains. [Objective] To study the biological characteristics of the strains, develop and utilize the strains in a reasonable way, and ensure the safety of strain application in production. [Methods] After activation, five strains of LAB and three strains of Bacillus were identified. Their morphology was observed, and the growth curve, acid production, and optimal growth conditions of the strains were investigated. Furthermore, the antimicrobial activity, enzyme production, probiotic properties, and safety of the strains were measured. [Results] The strains R1-R5 of LAB were identified as Lactobacillus casei, L. paracasei, L. farcimini, L. futsaii, and L. salivarius, respectively. The strains Y1-Y3 of Bacillus were identified as B. velezensis, B. subtilis, and B. licheniformis, respectively. The eight strains presented different morphological structures but all were rod-shaped and entered the logarithmic growth stage and platform stage after being cultured for 2-10 h and 18-24 h, respectively. After incubation for 24 h, LAB and Bacillus maintained the viable counts at 10⁹ and 10⁸ CFU/mL, respectively, and the optimal growth at 37.0℃. LAB had strong acid-producing ability and antimicrobial activity, and Bacillus had strong enzyme production. All the strains demonstrated strong tolerance in artificial gastric juice, no hemolytic activity, no virulence gene, and moderate sensitivity to antibiotics. Among them, L. salivarius carried tetracycline resistance genes, while it was moderately sensitive to tetracycline. [Conclusion] The eight strains of bacteria have fast growth and reproduction. LAB have strong acid-producing ability and antimicrobial activity, and Bacillus has strong enzyme-producing performance. With good probiotic properties and safety in vitro, the 8 strains can be applied in production.

Abstract:[Background] Bacterial fruit blotch is a prevalent quarantine disease caused by Acidovorax citrulli in cucurbit crops. A. citrulli secretes the key pathogenic factor, known as type III effectors (T3Es), into plant cells via the type III secretion system (T3SS). However, the pathogenesis of T3Es remains elusive. In previous studies, we have identified several candidate T3Es in A. citrulli FC440. [Objective] To reveal the sequence features, transport characteristics, and the role in the pathogenic process of the candidate T3E AopBF1 from A. citrulli FC440 strain, so as to lay a theoretical foundation for dissecting the mechanism of pathogenesis. [Methods] Bioinformatic tools were used to predict and analyze the T3E sequence characteristics of AopBF1. Then, RT-qPCR and an avirulent protein reporter system analysis were conducted to reveal the regulation and transport characteristics of AopBF1. The pathogenicity of aopBF1 mutant (insertion mutation) and overexpressing strain was investigated to unveil the role of AopBF1 in pathogenicity. [Results] AopBF1 had the typical T3E characteristics, possessing a protein kinase domain and no other conserved domain. The expression of AopBF1 was significantly down-regulated in the mutants of the T3SS core regulatory genes hrpX and hrpG. The co-expression of aopBF1 and the AvrBs1 functional region (59-445 aa) in the avrBs1 mutant induced hypersensitive reactions (HRs) in the leaves of ECW-10R pepper containing the Bs1 protein. The pathogenicity of the aopBF1 mutant in cucumber was significantly reduced, while the accumulation of hydrogen peroxide, superoxide anion radical, and callose significantly increased. The overexpression of aopBF1 significantly enhanced the pathogenicity and delayed HRs in Nicotiana benthamiana. The AopBF1 transiently expressed in N. benthamiana was localized in the cytoplasm, nucleus, and cell membrane, and then induced HRs and up-regulated the expression of PTI and hormone pathway-related genes. [Conclusion] AopBF1 is demonstrated to be a T3E with a protein kinase domain in A. citrulli. It can inhibit PTI immune responses such as host reactive oxygen species and callose accumulation to enhance the pathogenicity of A. citrulli and can trigger PTI and hormone-related immune responses in N. benthamiana containing R proteins.

Abstract:[Background] The special habitat of the Qinghai-Xizang Plateau harbors the microbial resources with strong tolerance to stress. [Objective] To explore the wheat (Triticum aestivum) growth-promoting effect of Bacillus in the special habitats of Qinghai-Xizang Plateau. [Methods] The 16S rRNA gene and gyrB of the strain WL911 isolated from the rhizosphere of Tamarix ramosissima in Haixi Mongolian and Tibetan autonomous prefecture, Qinghai province were identified. The tolerance of the strain to low temperature was examined. The growth-promoting effect of the WL911 suspension (concentration of 1×10⁷cfu/mL) on the seedlings of the wheat cultivar ‘Qingmai 7’ at 4℃ was determined. Illumina HiSeq×10 was used for the whole genome sequencing of the strain, which was followed by functional gene annotation and analysis. [Results] The strain WL911 was identified as Bacillus velezensis and could tolerate the low temperature of 4℃. It had a significant growth-promoting effect on the growth of ‘Qingmai 7’ seedlings. At 26℃, the strain increased the plant height, root length, and fresh weight of the seedlings by 12.22%, 50.12%, and 70.99%, respectively. At 4℃, the strain increased the chlorophyll content by 19.72% and decreased the accumulation of H₂O₂ and malondialdehyde by 23.50% and 40.68%, respectively, while increasing the biomass of the seedlings. At the same time, it increased the activities of superoxide dismutase, peroxidase, and catalase by 45.82%, 17.35%, and 14.18%, respectively. The genome size of WL911 was 3 915 549 bp, with the G+C content of 46.47%. The functional genes annotated by gene ontology accounted for 75.74% of the total genes. Specifically, the strain carried growth-promoting genes such as glnB, yclQ, and fetB, which participated in the synthesis of growth hormone and nutrients; it carried mnhA, mnhE, pheT, pheS and proV involved in Na⁺ efflux, proline synthesis, and phenolic compound; and it carried a key gene cspA encoding the cold shock proteins CspC, CspB, and CspD. [Conclusion] B. velezensis WL911 (GenBank accession number:OP874802) serves as a strain for the research and development of high-quality biological fertilizers.

Abstract:[Background] Effective microorganisms (EM) have been widely used in the farming in China, while the available information is limited regarding the impacts of EM biofertilizer on the growth and rhizosphere bacterial community structure of pigment pepper. [Objective] To clarify the growth-promoting effect of EM biofertilizer on pigment pepper in Xinjiang of China and uncover the influence of the biofertilizer on rhizosphere bacterial community structure. [Methods] The EM biofertilizer was inoculated into the roots of pigment pepper plants through irrigation. We determined the growth indexes, soil nutrient levels, and enzyme activities at the harvest stage to assess the impacts of EM biofertilizer on the pepper growth and soil quality. High-throughput sequencing of 16S rRNA was employed to investigate the impacts of EM biofertilizer on the composition and structure of rhizosphere bacterial community. [Results] Compared with the control group, the application of EM biofertilizer increased the plant height, fresh weight, single fruit weight, and number of fruits per plant by 23.89%, 85.41%, 42.31%, and 46.04%, respectively. Moreover, it increased the available nitrogen, the available phosphorus, and the activities of urease, sucrase, and peroxidase in the soil by 5.83%, 13.39%, 11.47%, 9.42%, and 21.43%, respectively. The application of EM biofertilizer significantly altered the alpha and beta diversity of bacteria in the rhizosphere soil and increased the relative abundance of beneficial bacteria including Proteobacteria, Acidobacteria, Gemmatimonadetes, Actinobacteria, and Firmicutes. Especially, the relative abundance of Xanthomonadaceae belonging to Proteobacteria was increased by 119.32%. At the genus level, the application of EM biofertilizer increased the relative abundance of Luteitalea, Luteimonas, Sphingobacterium, and Halomonas. Among them, the relative abundance of Luteimonas was increased by 244.17%, whereas that of Flavobacterium was lower than that in the control group. The microbial taxa showing positive correlations with soil physicochemical indices presented significantly increased relative abundance after the application of EM biofertilizer. [Conclusion] The application of EM biofertilizer regulates the rhizosphere microbial community structure by changing soil nutrient levels and enzyme activities, which further enriched beneficial bacteria with strong survival ability in saline-alkali land and promoted the growth of pigment pepper.

Abstract:[Background] The thioredoxin reductase (TRR), one of the key components in the thioredoxin system, plays a key role in the oxidative stress response, homeostasis, and infection of pathogens.[Objective] To examine the role of TRR in the infection of Streptococcus suis type 2 (SS2), a zoonotic pathogen. [Methods] The trr-deleted mutant (Δtrr) and complementation strain (cΔtrr) of SS2 were constructed by homologous recombination on the basis of the wild-type (WT) strain HA9801. The Gram staining, plate counting, and cell and mouse infection assays were employed to examine the morphological characteristics, stress resistance, and infection process of the strains. [Results] The deletion of trr showed no effect on the morphological or growth characteristics of SS2, while it enhanced the tolerance to heat, oxidative, and acid stress conditions compared with WT. Δtrr presented reduced adhesion on murine epithelial cells and invasion capacity in cerebrovascular endothelial cells. It was easily to be phagocytosed and presented lower pathogenicity in RAW264.7 cells and mice. [Conclusion] TRR is involved in the stress responses, adhesion, and invasion and serves as a novel virulence factor for SS2.

Abstract:[Background] Silkworm (Bombyx mori) midgut polyhedrosis is a highly infectious and harmful viral disease caused by B. mori cytoplasmic polyhedrosis virus (BmCPV). Which virus has strong resistance, a wide host range, and is difficult to control and prevent. [Objective] To investigate the occurrence of silkworm midgut polyhedrosis in the sericultural region of Guangxi and study the pathogenicity, morphological characteristics, and molecular information of BmCPV, so as to provide a basis for the effective control of silkworm midgut polyhedrosis. [Methods] The anatomical and microscopic examinations of the diseased silkworm were combined to reveal the incidence of silkworm midgut polyhedrosis, and the median infectious concentration (IC₅₀) of BmCPV on silkworm was investigated via biological tests. The external morphology of BmCPVwas observed by optical microscopy and scanning electron microscopy, and the internal structure by transmission electron microscopy. PCR amplification and sequencing were employed to identify the BmCPV. [Results] Silkworm midgut polyhedrosis was prevalent in the sericultural region of Guangxi, with the incidence rate of 6.06% and 13.02% in Jinchengjiang and Donglan, respectively, and the highest incidence of 30.41%. Two BmCPV strains, BmCPV-J and BmCPV-D, were isolated from the diseased silkworm in the two sericultural regions, with the IC₅₀ of 4.88×10³ PIBs/mL and 1.63×10⁴ PIBs/mL, respectively, which indicated strong pathogenicity. BmCPV-J and BmCPV-D were hexagonal polyhedra with the diameters of 1.0-3.4 μm, differences in size between polyhedra, the spherical virion diameters of 30-50 nm, and spiny protuberances. PCR was conducted with the primers designed based on the RNA replicase gene of BmCPV. The fragment of BmCPV-J was identical with that of BmCPV reference strain, while that of BmCPV-D had two base differences. [Conclusion] Silkworm midgut polyhedrosis is a serious disease in the sericultural region of Guangxi, and its pathogen has strong infectivity and wide distribution. BmCPV-J and BmCPV-D with typical characteristics of CPV which belong to BmCPV. The results provide an important basis for the effective control of silkworm midgut polyhedrosis.

Abstract:[Background] Stellaria dichotoma var. lanceolata has an important medicinal value, and its quality can be evaluated based on the total sterols and total flavonoids. [Objective] To explore the endophytic microbial community characteristics in the root of S. dichotoma var. lanceolata growing in different habitats and the relationship of the microbial community structure with the main components and yield of the medicinal herb. [Methods] We employed the high-throughput sequencing and conventional determination methods of medicinal materials to analyze the characteristics of the endophytic microbial community in the roots of S. dichotoma var. lanceolata in different habitats of semi-fixed aeolian sandy soil (SFA), lithosol (LI), and loessal (LO). [Results] The dominant endophytic bacteria were Actinobacteriota and Proteobacteria, and the dominant fungi were Ascomycota and Basidiomycota. The dominant endophytic microbial genera varied depending on the habitats. The content of total sterols and total flavonoids was higher in the LI habitat, while the dry weight per plant and the dry weight-to-fresh weight ratio were higher in the SFA habitat. Spearman correlation analysis suggested that there were rich endophytes represented by metagenome_g__norank_f__67-14 (endophytic bacteria) and unclassified_p__Ascomycota (endophytic fungi) showing significantly positive correlations with the main medicinal components and yield of S. dichotoma var. lanceolata. [Conclusion] The endophytic microbial taxa associating with the key active components of S. dichotoma var. lanceolata have a broad research value in species identification and extraction, strain culture, and secondary metabolite analysis. This study provides a theoretical reference for the development of high-quality medicinal materials in the suitable producing areas of S. dichotoma var. lanceolata.

Abstract:[Background] Bacillus rugosus A78.1 isolated from the fibrous roots of healthy Glycyrrhiza uralensis Fisch. has high β-glucosidase activity. [Objective] To investigate the genetic information of the isolate for enzyme production and provide data support for the further research and industrial application of the strain. [Methods] A β-glucosidase-producing Bacillus strain was screened by the medium supplemented with esculin. Nanopore PromethION and Illumina NovaSeq were used for genome sequencing and assembly, and the potential β-glucosidase genes of the strain were predicted by gene prediction and functional annotation. In addition, the effects of carbon source, nitrogen source, inoculum amount, temperature, and initial pH on the enzyme-producing activity of the strain were investigated with β-glucosidase activity as an indicator. [Results] A strain capable of producing β-glucosidase was isolated from the fibrous roots of G. uralensis. It was identified as a strain of Bacillus by morphological observation, physiological and biochemical tests and named B. rugosus A78.1. The genome of this strain was 4 146 938 bp in length, with the G+C content of 43.86%, encoding 4 255 genes. In the genome, 192 carbohydrate-active enzyme genes were annotated, including 10 β-glucosidase genes belonging to the GH1 and GH3 families. A total of 2 896, 4 019, and 3 657 genes were annotated in GO (gene ontology), KEGG (Kyoto encyclopedia of genes and genomes), and COG (clusters of orthologous groups of proteins), respectively. The genome sequencing data were submitted to NCBI and obtained the GenBank accession No. CP096590. For the production of β-glucosidase, the strain should be fermented with 0.5% glucose as the carbon source, 1.0% yeast extract as the nitrogen source at 37℃ and pH 6.0 with the inoculum amount of 3%. Under these conditions, the activity of β-glucosidase produced by this strain reached (5.640±0.085) U/mL. [Conclusion] We confirmed the excellent β-glucosidase-producing ability of B. rugosus A78.1 and the potential of this strain in carbohydrate metabolism by whole genome sequencing and fermentation condition optimization for enzyme production. The findings provide a basis for the research and application of this strain in biochemical and food fields such as cellulose degradation and glycoside hydrolysis.

Abstract:[Background] Antimicrobial resistance poses a huge threat to global health and economic development. Tigecycline is one of the important drugs for treating severe infections caused by multidrug-resistant Enterobacteriaceae. However, the mobile resistance gene tet(X3), which could mediate high-level tigecycline resistance, was discovered in 2019. Outer membrane vesicles have been recognized as a new route for horizontal gene transfer, while little is known about the role of outer membrane vesicles in the disseminating of tet(X3). [Objective] To investigate the effects of different antimicrobials on the production and characteristics of outer membrane vesicles of tet(X3)-positive tigecycline-resistant Acinetobacter baumannii strain 34AB. [Methods] The antimicrobial susceptibility was determined by the broth micro-dilution method. The bacterial outer membrane vesicles were extracted by ultracentrifugation. The protein concentration of the outer membrane vesicles was determined by the BCA method, and the size and potential tested by Zeta-sizer nano-ZS. The copy number of tet(X3) within the outer membrane vesicles was determined by RT-qPCR. [Results] Compared with the control group without antibiotic treatment [(0.64±0.04) mg/mL], antimicrobials at 1/2 MIC or 1/4 MIC increased the production of outer membrane vesicles, with the effects of ceftazidime [1/2 MIC, (2.83±0.57) mg/mL; 1/4 MIC, (2.38±0.29) mg/mL] and meropenem [1/2 MIC, (2.19±0.11) mg/mL; 1/4 MIC, (1.96±0.37) mg/mL] being the most significant (P<0.01). Meanwhile, the antimicrobial treatments decreased the size and potential of outer membrane vesicles and increased the copy number of tet(X3) (2.80×10⁴-2.63×10⁷copies/μL). [Conclusion] The clinical application of antimicrobials may increase the production and the antimicrobial resistance gene abundance of outer membrane vesicles, thereby increasing the risk of them as vectors for disseminating of antimicrobial resistance genes.

Abstract:[Background] Influenza A virus (IAV) can activate multiple programmed cell death pathways, which play important roles in the host defense system. Ferroptosis is a novel non-apoptotic type of cell death and mainly mediated by iron-dependent lipid peroxidation. [Objective] To explore the mechanism of IAV-induced ferroptosis via the HIF-1α/iNOS/VEGF signaling pathway. [Methods] Mouse lung epithelial (MLE-12) cells were infected with IAV to establish a cell injury model, and the virus titer and inflammatory cytokine secretion were examined. The fluorescence probe and colorimetric methods were used to measure the levels of reactive oxygen species (ROS), superoxide dismutase (SOD), total iron ions, and ferrous ions. Transmission electron microscopy was employed to observe the cell ultrastructure. The mRNA and protein levels of cell ferroptosis markers were determined. Bioinformatics tools were used to predict the potential mechanism of IAV-induced ferroptosis. Laser confocal microscopy was employed to observe the effect of IAV on the expression of hypoxia-inducible factor-1α (HIF-1α) in cells, and the mRNA and protein levels of the proteins involved in the HIF-1α/iNOS/VEGF signaling pathway were determined. A HIF-1α knockdown model was established to explore the role of the HIF-1α/iNOS/VEGF signaling pathway in IAV-induced cell ferroptosis. [Results] The ferroptosis inhibitor reduced the virus titer and inflammatory cytokine secretion of IAV-infected cells. Moreover, in lowered the levels of ROS, total iron ions, and ferrous ion, increased the SOD activity, repaired mitochondrial damage, and reversed the mRNA and protein levels of ferroptosis markers. Bioinformatics predicted that the HIF-1α/iNOS/VEGF signaling pathway was closely associated with IAV-induced ferroptosis. IAV infection promoted the activation and nuclear translocation of HIF-1α in cells and up-regulated the mRNA and protein levels of HIF-1α, vascular endothelial growth factor (VEGF), and inducible nitric oxide synthase (iNOS). [Conclusion] IAV infection can induce cell ferroptosis by activating the HIF-1α/iNOS/VEGF signaling pathway.

Abstract:[Background] The oral microbiota changes have significant correlations with oral diseases and systemic diseases in pregnant women. [Objective] To compare the oral microbiota structure of females in different pregnancy states and explore the correlation between the structure difference and different pregnancy states. [Methods] Eighteen pregnant women and nine non-pregnant women were selected for the study and assigned into three groups (n=9):gestational diabetes mellitus (GDM, mean age of (28.9±3.6) years, mean pregnancy of (30.1±3.2) weeks), non-diabetic pregnant women (PW, mean age of (27.9±3.0) years, mean pregnancy of (28.6±4.7) weeks) and non-pregnant women (NPW, mean age of (27.7±2.1) years). Oral saliva (S) and supragingival dental plaque (D) samples were collected. The Illumina Novaseq platform was used to sequence the V3-V4 variable region of bacterial 16S rRNA. SILVA was used for the taxonomical annotation of the characteristic sequences, and QIIME was employed to perform the bioinformatics analysis. [Results] The D-GDM samples had higher detection rate of Capnocytophage and lower detection rate of Selenomonas than the D-PW samples. The S-GDM samples had higher detection rate of anaerobic bacteria such as Aeromonas and Bacteroides than the S-PW samples and lower detection rate of Veillonella than the S-PW samples. The D-PW samples had higher detection rates of Leptotrichia, Prevotella, and Selenomonas and lower detection rates of Aeromonas, Actinobacillus, Capnocytophage, Neisseria, Lautropia, and Streptococcus than the D-NPW samples. The S-PW samples had lower detection rate of Veillonella, Prevotella, Streptococcus, and Porphyromonas than the S-NPW samples. The D-GDM samples had high detection rate of Tannerella and Leptotrichia and lower detection rate of Roseburia than the D-NPW samples. The S-GDM samples had high detection rates of Treponema and Campylobacter and lower detection rate of Streptococcus than the S-NPW samples. At the species level, the S-GDM samples had higher detection rate of Fusobacterium nucleatum, similar detection rates of Porphyromonas gingivalis and Tannerella forsythia, and lower detection rate of Prevotella nigrescens than the S-PW samples. The S-PW samples had high detection rates of P. gingivalis, P. nigrescens, and T. forsythia than the S-NPW samples.[Conclusion] GDM will increase the detection rate of anaerobic bacteria in the oral cavity, and the correlations between GDM and periodontitis-causing bacteria such as P. gingivalis, T. forsythia, and P. nigrescens are uncertain.

Abstract:[Background] Pyroptosis is a form of programmed cell death. Gasdermin (GSDM) can be cleaved by cysteinyl aspartate-specific caspase (protease) in archaea and bacteria, which results in cell disruption, similar to the effects of pyroptosis in eukaryotes.[Objective] Cell disruption is a crucial step in synthetic biology, metabolic engineering, and biomanufacturing. Utilizing pyroptosis as a cell disruption method can simplify the operation and improve the production efficiency compared with the conventional methods.[Methods] Protease and GSDM from different sources were co-expressed in Escherichia coli BW25113. The GSDM with obvious pyroptosis effect from Runella sp. was selected for protein truncation, so that it could directly activate pyroptosis effect after inducing the expression of truncated protein (GSDMJD). After overexpression of GSDMJD and optimization, an E. coli strain with controllable pyroptosis effect was obtained. Furthermore, sucrose phosphorylase was used to verify the effects of this system and ultrasonic disruption on enzyme activity. [Results] The regulation of pyroptosis was successfully implemented in E. coli. After the strain was induced to express the pyroptosis-related protein for 2 h, the cells were disrupted and released the contents. The above system and ultrasonic method were applied to the preparation of crude liquid of sucrose phosphorylase. The relative activity of crude enzyme liquid prepared by the pyroptosis method was significantly higher than that of crude enzyme liquid prepared by the ultrasonic method. In the case of OD₆₀₀ 2.0, the crude enzyme liquid prepared by the pyroptosis method had the highest enzyme activity, which increased by 60% compared with that of the crude enzyme liquid prepared by the ultrasonic method. [Conclusion] Pyroptosis serves as a simple, fast, and environmentally friendly method for microbial cell disruption, laying a foundation for the development of synthetic biology and metabolic engineering.

Abstract:[Background] Microbiota is closely related to the occurrence and development of lung cancer, and the field of study has become a hotspot. [Objective] This study seeks to conduct a comprehensive bibliometric analysis of the literature elucidating the associations between microbiota and lung cancer. Its aims include unveiling the present research status, identifying future trends, and offering a compass for subsequent investigations. [Methods] Literature data were sourced from the Web of Science Core Collection (WOSCC), China National Knowledge Infrastructure (CNKI), Wanfang Data, and VIP database for Chinese technical periodicals (VIP) databases. Furthermore, we used CiteSpace and VOSviewer to visualize the annual publications, countries/regions, and keywords. [Results] A total of 143 Chinese-language publications and 278 English-language publications were included. Notably, China stood out as the most prolific contributor. Keywords analysis showed that lung cancer, gut microbiota, and immunotherapy were research hotspots in this field. [Conclusion] In the past two decades, the vital role of microbiota in the etiology, diagnosis, and treatment of lung cancer has been recognized. Through the comparison of these databases, we found that the hot topics in this field are essentially the same in domestic and foreign. However, this field remains in the early stage, characterized by relatively immature studies and a lack of extensive, close international collaboration. Future studies on the frontier hotspots in this sector need to be strengthened much more. The findings of this study are helpful for researchers to better understand the frontier hotspots and development trends in this area, and provide a reference for the in-depth exploration of future research.