Abstract:Bacteriophages, a group of viruses that infect bacteria, have common features with eukaryotic viruses in the biological properties, such as morphology, size, and structural composition. The laboratory operation on bacteriophages is simple and has high safety, which demonstrates great advantages in culture, counting, stability, and susceptibility. Therefore, the research and application of bacteriophages as the indicator viruses for simulating or substituting eukaryotic viruses has attracted wide attention with certain progress achieved. This paper introduces the advantages of bacteriophages as indicator viruses and summarizes the feasibility evidence, cases, and difficult problems of bacteriophages application in the virus removal evaluation, disinfection effect evaluation, research on virus transmission patterns, and environment and water quality monitoring. In addition, considering the shortcomings, this paper puts forward suggestions and prospects for the research and application of bacteriophages as indicator viruses in the future.

Abstract:Legionella pneumophila, the causative agent of the severe pneumonia known as Legionnaires’ disease, uses its IVB secretion system to transport effector proteins into host cells. The effectors interact with host proteins and lipids to form a unique bacterial phagosome, Legionella-containing vacuole (LCV), which is required for the growth of Legionella in host cells. Phosphatidylinositols (PIs), a group of essential lipids for cells, are involved in signal transduction and vesicle transport. The available studies have demonstrated that L. pneumophila uses its effectors to regulate the host PI metabolism and the lipid composition of LCV membrane to promote the LCV maturation. We review the studies about the pathogenesis of L. pneumophila and the modulation of host PI metabolism and the related enzymes by the effectors of L. pneumophila, expecting to provide a reference for further understanding the regulation mechanisms of host lipid metabolism by Legionella.

Abstract:Lytic polysaccharide monooxygenases (LPMOs) are newly discovered copper ion-dependent oxidases, which play an important role in the enzymatic hydrolysis of biomass. Therefore, LPMOs have been described as biomass deconstruction boosters. LPMOs bind to specific substrates, and their catalytic mechanism has not been fully elucidated. Although there are many studies involving LPMOs, few of LPMOs have been applied to industrial biomass conversion, which poses challenges for their expression, regulation, and application. We comprehensively review the recent advances in LPMOs from the aspects of discovery and classification, catalytic mechanism, and relationship between structure and function. Further, we systematically summarize the activity determination and recombinant expression methods of LPMOs. Finally, we introduce the applications of LPMOs in different fields and put forward the future research directions. This review helps deepen the systematic understanding and promote the research and engineering of LPMOs, which will provide reference for the application of LPMOs.

Abstract:Symbiotic microorganisms regulate host chemical communication by affecting the synthesis and perception of insect semiochemicals, which in turn influences insect communication, defense, predation, and dispersal behavior. The effect of microbial symbionts on host chemical communication facilitates the spread of microorganisms, but could be beneficial or detrimental to the host, and provides the impetus for the co-evolution of symbiotic systems. In this paper, we review recent studies on the effects of microbial symbionts on insect chemoreception and their mechanisms, and analyze their evolutionary significance, aiming to provide supplementary information to the theory of insect chemical ecology and provide insight into the development of new pest control strategies.

Abstract:Lycopene, which is rich in tomatoes, has diverse functions and high nutritional value. Thus, it is of great significance to explore the health-enhancing effect of lycopene through intestinal microbiota and its mechanism. In this review, we summarized the physicochemical properties, digestion, absorption, and metabolism of lycopene, and particularly the influence of lycopene on the types, quantity, and metabolites of gut microbiota in the host. Furthermore, we discussed the intervention of gut microbiota in host inflammation, cardiovascular diseases, non-alcoholic fatty liver disease, and cancer development under the regulation of lycopene. This review may provide ideas and directions for the future exploration of tomato nutrition and product development.

Abstract:The type VI secretion system (T6SS), a powerful tool of bacteria, is involved in inter-bacterial competition and affects host life activities by injecting effector proteins into prokaryotic or eukaryotic cells. T6SS is ubiquitous in Gram-negative bacteria, mainly existing in Proteobacteria. Although most studies of T6SS have focused on animal bacteria, its role in plant-associated bacteria cannot be ignored. We introduced the T6SS of plant-associated bacteria in detail and summarized the latest research achievements from four aspects: the discovery of T6SS, the role of T6SS in the competition among plant-associated bacteria, the role of T6SS in the interactions between bacteria and plants, and the role of T6SS in the biocontrol of plant diseases. This review aims to provide guidance for the future research on the biological functions and applications of T6SS in plant-associated bacteria.

Abstract:Innate immunity is the first line of the host against invasion of foreign pathogens, and pattern recognition receptors (PRRs) are key receptors mediating innate immune response. PRRs activate the innate immune response of the host by recognizing pathogen associated molecular patterns (PAMPs). Among them, there is a milestone discovery in the field of DNA recognition and innate immunity in the 21^st century—cyclic GMP-AMP synthase (cGAS), which plays an important role in the host innate immune process. cGAS mediates the activation of stimulator of interferon genes (STING) by recognizing foreign DNA and producing a second messenger 2′,3′-cyclic GMP-AMP (2′,3′-cGAMP), thus promoting the secretion of downstream interferon and other cytokines to play an antiviral role in the host. Recent studies have found that the cGAS/STING pathway plays an important role in the host’s resistance to bacterial infection. Meanwhile, bacteria have also evolved different mechanisms to antagonize the cGAS/STING pathway. This paper mainly reviewed the biological functions of the cGAS/STING pathway and its role in bacterial infection, providing theoretical references for the further development of new antibacterial drugs.

Abstract:[Objective] To promote the production of γ-aminobutyric acid (GABA) by an endophytic yeast Wickerhamomyces rabaulensis JT229 isolated from plants in Tibet. [Methods] The D1/D2 region sequence of 26S rRNA gene was used for strain identification. Glucose and xylose were tested for GABA production. In addition, stress treatments, including high temperature and high concentration of ethanol and acetic acid, were investigated to increase the extracellular production of GABA by the strain. [Results] Wickerhamomyces sp. JT229 was identified as Wickerhamomyces rabaulensis, which produced GABA using glucose and xylose, and the GABA production was enhanced under the moderate stress of high temperature, acetic acid and ethanol. The extracellular production of GABA was 80.07, 67.02 and 104.15 mg/L under the above stress conditions, which were 2.15, 1.85 and 2.87 times those of the control conditions, respectively, and the intracellular accumulation of GABA was also detected. Under the conditions of 5 g/L acetic acid and 37 °C, the intracellular ROS level and cell membrane permeability increased more markedly than those under the control conditions. Compared with the control group, 3 g/L acetic acid lowered the intracellular ROS level while enhanced the cell membrane permeability. Under 37 °C, the content of intracellular GABA dropped. Therefore, we inferred that the increased extracellular production of GABA was resulted from its increased intracellular secretion. [Conclusion] This is the first time that endophytic W. rabaulensis was identified. We revealed that W. rabaulensis strain JT229 isolated from Tibet had the potential to produce GABA, and also demonstrated the enhanced production of GABA under stress treatments. The results facilitated further development and utilization of yeast strains for production of GABA and GABA-containing products.

Abstract:[Objective] To investigate the role of type VI secretion system (T6SS) effector protein Clpv in the pathogenesis of Salmonella typhimurium.[Methods] We cloned the clpv gene from SL1344 genome of S. typhimurium and compared it with the clpv genes of other Gram-negative bacteria (Pseudomonas taiwanensis, Raoultella planticola, Listonella anguillarum, Pantoea ananatis, Actinomyces viscosus, and Escherichia coli). The clpv gene was cloned into pEGFP-N1 vector to construct the recombinant plasmid pEGFP-Clpv. The protein expression, localization, and the induced M1 and M2 polarization of mouse macrophages were detected by Western blotting, q-PCR, fluorescence microscopy, and flow cytometry. [Results] The clpv gene was 2 637 bp, showing the highest homology to clpv of P. taiwanensis. Western blotting, q-PCR, and immunofluorescence showed that the recombinant protein was about 120 kDa and apparent green fluorescence in cells was found. The protein was located primarily in cell membrane. The results of q-PCR and flow cytometry indicated that Clpv enhanced M1 polarization (P<0.01) but weakened M2 polarization of mouse macrophages (P<0.01). [Conclusion] The T6SS effector protein Clpv of S. typhimurium was cloned and expressed, and its intracellular localization and effect on macrophage polarization were clarified.

Abstract:[Objective] Extracellular polysaccharides, indispensable components of biofilm, play a role in bacterial pathogenicity and antibiotic resistance. Targeted elimination of the core extracellular polysaccharides of biofilm by enzyme preparations can fundamentally destroy the core skeleton of the biofilm and help overcome the harm caused by biofilm. [Methods] On the basis of the rich gene sequence information in the NCBI database, we screened the hydrolases targeting the extracellular polysaccharides Pel, Psl, algin, Poly-β(1,6)-N-acetyl-d-glucosamine (PNAG), and cellulose in the biofilm. Further, we employed the bioinformatics tools such as phyre2 and SWISS-MODEL to analyze the physical and chemical properties, genetic evolution, functional domains, and three-dimensional structures of these hydrolases. [Results] A total of 153 hydrolases targeting extracellular polysaccharides in biofilm were screened out and their sequence information was obtained. Among them, 30, 25, 33, 30, and 35 hydrolases targeted Pel, Psl, algin, PANG, and cellulose, respectively, which belonged to the glycoside-hydrolase family GH114, Glyco_hydro superfamily, AlgLyase superfamily, glycoside-hydrolase family GH13, and glycosyl hydrolase family GH8.[Conclusion] These hydrolases have the potential to cleavage the core extracellular polysaccharides in biofilm and need to be further developed and applied. This study provides the most comprehensive sequence and biological information of hydrolases targeting core extracellular polysaccharides in biofilms so far, laying a solid data foundation for precise prevention and targeted control of biofilms.

Abstract:[Objective] The DNA-binding protein HU is a histone-like protein involved in the recombination and repair of bacterial DNA and plays a regulatory role in the transcription of bacteria, whereas the role of this protein in the physiological activities of bacteria remains unknown. In order to learn more about the HU protein, we investigated the physiological function of HupB. [Methods] We constructed a hupB-deleted strain of Aeromonas hydrophila by using homologous recombination technology and then determined the physiological phenotype of the strain. [Results] The deletion of hupB gene significantly enhanced the hemolysis, extracellular protease activity, and motility, while it significantly reduced the biofilm formation. The biofilm formation was restored in ΔhupB::hupB. Further, label-free quantitative proteomics analysis was performed to study the differentially expressed proteins between the wild type and ΔhupB, which revealed 235 up-regulated proteins and 224 down-regulated proteins in ΔhupB. The bioinformatics analysis showed that the differentially expressed proteins were involved in a variety of biological processes such as protein translation, biofilm formation, and signal transduction. [Conclusion] The HupB protein can remarkably affect the biofilm formation of A. hydrophila. The results provide a theoretical basis for better understanding the regulatory role of HupB in the physiological activities of A. hydrophila.

Abstract:With the popularity of plastics in the human society, more and more waste plastics and their precursors are left in the environment. In view of the slow degradation of the plastics in the natural environment, it is in urgent need to develop an effective degradation pathway. [Objective] To investigate the responses of the gut microbiota and metabolic pathways in Tenebrio molitor larvae to the feeding of polystyrene, and find an effective way to biodegrade and utilize polystyrene through food intake. [Methods] The larvae were fed with polystyrene as the only food source, and the survival rate and body weight of the larvae were recorded. The changes in the structure of gut microbiota were analyzed by 16S rRNA gene sequencing of the gut contents. Kyoto encyclopedia of genes and genomes (KEGG) enrichment was performed to predict the relevant functional genes. [Results] The survival rate and body weight of the T. molitor larvae fed with polystyrene decreased, and polystyrene plastic was significantly reduced. The abundance and diversity of gut microbiota significantly decreased in the T. molitor larvae fed with polystyrene. The dominant phyla in the gut were Proteobacteria, Tenericutes, and Firmicutes, and the dominant genera were Spiroplasma, Enterobacillus, and Escherichia-Shigella. KEGG analysis predicted a total of 18 genes involved in aromatic and alkane degradation. The abundance of the pathways associated with polystyrene degradation by the gut microbiota of T. molitor larvae feeding on polystyrene increased and the expression of related genes was up-regulated. [Conclusion] Polystyrene can provide certain material and energy for the growth and development of T. molitor larvae and enable them to complete a generation. After the larvae feed on a single food source for a long time, their gut microbiota structure will undergo targeted changes. KEGG prediction can identify the genes associated with polystyrene metabolism, which provides a valuable basis for the subsequent research.

Abstract:[Objective] Ultraviolet B (UVB) irradiation is one of the main environmental causes of skin photoaging and hyperpigmentation. Lactobacillus plantarum is a well-studied species of probiotics that can benefit human health. The present study investigated the anti-photoaging and anti-melanogenesis effects of heat-inactivated L. plantarum (LP) ATCC 8014 on the skin cells (normal human dermal fibroblast (NHDF) cells and B16F10 murine melanoma cells) exposed to UVB irradiation. [Methods] The viability, DNA damage, and reactive oxygen species (ROS) levels of NHDF and B16F10 cells were determined by methyl thiazolyl tetrazolium (MTT) assay, terminal-deoxynucleoitidyl transferase dUTP nick end labeling (TUNEL) assay, and 2′,7′-dichlorofluorescin diacetate (DCFH-DA), respectively. The level of collagen I in NHDF cells was determined by enzyme-linked immunosorbent assay (ELISA). The melanin production and tyrosinase activity in B16F10 cells were measured by NaOH lysis method and L-DOPA oxidation method, respectively. qRT-PCR and Western blotting were employed to measure the expression levels of genes and proteins associated with photoaging and melanin production. [Results] (1) LP inhibited UVB-induced cytotoxicity by reducing the ROS-mediated DNA damage in NHDF and B16F10 cells; (2) LP down-regulated the mRNA levels of matrix metalloproteinase (MMP)-1, MMP-3, and MMP-9 (rather than MMP-2), relating to inhibit the extracellular signal-regulated kinase (ERK), p38 (rather than JNK)/c-Fos (rather than c-Jun) signaling pathway. It up-regulated the protein level of procollagen type-1 alpha 1 (COL1A1), thereby increasing the content of type I collagen; (3) LP as an autophagy inducer (up-regulating the protein levels of LC3-II and Beclin 1 and increasing the LC3-II/LC3-I ratio) inhibited the activities and/or expression of tyrosinase, tyrosinase-related protein (TYRP)-1, and TYRP-2 by inhibiting the PKA/CREB/MITF signaling pathway, thereby decreasing the melanin content. [Conclusion] LP has potential anti-photoaging and anti-melanogenesis effects on the skin cells exposed to UVB.

Abstract:[Objective] To investigate the effect of the bio-organic fertilizer on heart rot and rhizosphere bacteria of pineapple. [Methods] Through high-throughput sequencing, we explored the bacterial diversity and community in rhizosphere of pineapple applied with different fertilizers. [Results] Compared with conventional fertilizer treatment (CK) and common organic fertilizer treatment (YJ), bio-organic fertilizer treatments of KN (sheep manure+peat soil+Bacillus subtilis) and KY (sheep manure+coconut chaff+B. subtilis) significantly reduced the incidence of heart rot in pineapple, especially KN. The α diversity of soil in KN and KY was higher than that of CK and YJ and a significantly different bacterial community structure emerged in the two bio-organic fertilizer treatments. Compared with CK, KN significantly increased the abundance of Bacteroidetes and Firmicutes, while the abundance of Acidobacteria, Chloroflexi, Gemmatimonadetes, and Nitrospirae in KY was significantly raised. At the genus level, the abundance of both Paraburkholderia and Flavobacterium in the bio-organic fertilizer treatments was significantly elevated. Variance partitioning analysis suggested that soil chemical properties (36.29%) had the greatest influence on the bacterial community, particularly soil available potassium and organic matter. In addition, the incidence (22.53%) and partial productivity of fertilizer (16.42%) were also the key influencing factors.[Conclusion] The application of bio-organic fertilizers (KN, KY) can change bacterial community structure in rhizosphere of pineapple and decrease the incidence of heart rot, which are important for the rhizosphere ecosystem stability and health of pineapple.

Abstract:[Objective] To establish a high-throughput multi-target technique based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for the detection of porcine pseudorabies virus (PRV), porcine circovirus types 2 (PCV-2) and 3 (PCV-3), African swine fever virus (ASFV), and porcine bocavirus group 1 (PBoV-G1), group 2 (PBoV-G2) and group 3 (PBoV-G3). [Methods] The primers for different pathogens and corresponding single-base extension probes were designed based on the conserved sequences in the genes of the seven pathogens. After the optimization of primer concentrations and reaction conditions, the specificity, sensitivity, and repeatability of the method were analyzed. Finally, this MALDI-TOF MS method was used to detect the pathogens in clinical samples and porcine products. [Results] The established method only produced target peaks in the detection of specific virus-positive samples, and there was no cross-reaction with other pathogens, which indicated that the method had good specificity for the detection of the seven target viruses. The repeatability test results showed that the positive coincidence rate of each virus in high, medium, and low concentrations was ≥98.0% within batches and ≥98.3% between batches, indicating that the method had high repeatability. The low limits of detection of the established method for the seven pathogens in the system were within the range of 8.65-26.27 copies/μL, which was comparable to that of the real-time fluorescence quantitative PCR (RT-qPCR). The established MALDI-TOF MS method was used to detect 100 tissue, feed, and pork samples, in which 39 samples were detected with two or more mixed infections, including five samples simultaneously positive for five pathogens. In addition, eight samples of artificial contamination with recombinant adenovirus carrying ASFV-p72 gene were tested, which showed ASFV-positive results. The coincidence rates of the results obtained by MALDI-TOF MS and RT-qPCR for the detection of different pathogens were as high as 94.4%-100%. [Conclusion] The method established based on MALDI-TOF MS for the detection of multiple porcine respiratory DNA viruses in this study provides a sensitive, specific, high-throughput and multi-target detection technique for rapid surveillance and differential diagnosis of porcine diseases, facilitating the import and export animal quarantine.

Abstract:[Objective] Gut fungal microorganisms play multiple roles in the life history of their hosts as indispensable part of gut microbiota. Although stag beetles are common saprophytic insects, little is known about their gut fungal community. In this study, we compared the structure and diversity of gut fungi at different developmental stages of the rainbow stag beetle, Phalacrognathus muelleri, aiming to reveal the characteristics of the fungi at different developmental stages of this insect. [Methods] We employed high-throughput sequencing (Illumina MiSeq) to study the gut fungal community structure in the newborn larvae, mature larvae, and adults of P. muelleri. Further, we analyzed alpha and beta diversity and carried out functional prediction for the fungi. [Results] The predominant fungal genera in the gut of P. muelleri were Candida, Phialocephala, Penicillium, and Lecythophora. The composition and diversity of the gut fungal community were significantly different between the larvae and adults, which may be associated with their different diets. The functional prediction showed that endosymbiotic fungi in the larval gut had higher diversity and relative abundance, suggesting that the larvae might depend more on the beneficial fungal taxa in the gut to obtain nutrients. The results of the abundance-based β-null deviation showed that the adult gut exerted a stronger filtering effect to select specific fungal taxa. Thus, the adults might build a more stable co-occurrence network of gut fungal community which supported them to adapt to the environmental fluctuations. [Conclusion] Different groups of functional fungi are involved in the food degradation of P. muelleri at different developmental stages. The larvae may depend more on gut fungi, and the adult gut has strong filtering effect to select specific groups of fungi and maintain the stability of the gut fungal community. Our study enhances our understanding of the gut microbiota of stag beetles, which can aid in the conservation and utilization of these saprophytic beetles as an important functional group in ecosystems.

Abstract:[Objective] To investigate the effects of nine polysaccharides on the proliferation and enzyme production characteristics of Bacillus coagulans. [Methods] B. coagulans was co-fermented with inulin polysaccharide, Eleutherococcus senticosus polysaccharide, chitosan oligosaccharide, Saposhnikovia divaricata polysaccharide, xylo-oligosaccharide, Astragalus polysaccharide, d-mannose, Atractylodes macrocephala Koidz polysaccharide, and Yu Ping Feng polysaccharide as the only carbon source in the medium, respectively. The optimal polysaccharides were screened based on the strain growth, enzyme activities, and in vitro anaerobic fermentation performance. [Results] B. coagulans could well utilize the polysaccharides of Astragalus, S. divaricata, A. macrocephala, and Yu Ping Feng. The significant differences in pH and protease activity (P<0.05) after fermentation were found between 4% A. macrocephala polysaccharide and 4% S. divaricata polysaccharide. After in vitro fermentation, the lactic acid content and total protease activity increased, which were the highest in the 4% A. macrocephala polysaccharide group (P<0.05). The results of 16S rRNA gene sequencing of intestinal contents fermentation liquid showed that B. coagulans fermented with Astragalus polysaccharide, S. divaricata polysaccharide, and d-mannose significantly reduced the relative abundance of pathogenic bacteria such as Aeromonas, α-Proteobacteria, Streptococcus, and Shigella and improved that of Lactobacillus, Firmicutes, Lactococcus lactis, and Acidobacteria compared with the control group. [Conclusion] B. coagulans fermented with 4% A. macrocephala polysaccharide has good enzyme production and probiotic properties, which has a good potential for application in aquatic feed.

Abstract:[Objective] Pacific white shrimp (Litopenaeus vannamei) raised in high-nitrite environment tend to have different growth rates and body weights between individuals at the end of the culture period. This study aims to investigate the association between growth variance with intestinal microbiota structure of shrimps raised in a high-nitrite environment. [Methods] Intestinal contents and seawater samples were collected from rapidly growing, normally growing, and slowly growing shrimps raised in a high-nitrite pond for 16S rRNA gene sequencing and linear discriminant analysis effect size (LEfSe). [Results] The intestinal microbial diversity of the slowly growing shrimps was different from that of rapidly and normally growing shrimps. The principal coordinate analysis showed that the intestinal microbiota structure of the normally growing shrimps was more similar to that of the rapidly growing shrimps than to that of the slowly growing shrimps. The results of LEfSe revealed that Flammeovirgaceae, Flavobacteriaceae, and Planctomycetaceae had high abundance in the shrimps with rapid growth, while Desulfovibrionaceae, Shewanellaceae, and Vibrionaceae were significantly enriched in the shrimps with slow growth. [Conclusion] The difference in nitrogen metabolism capacity of intestinal microorganisms leads to the growth variance among shrimps in the high-nitrite environment. The findings provide new knowledge for the industrial farming of shrimps.

Abstract:[Objective] This study explored the characteristics, network complexity and stability of the bacterial community harboring the alkaline phosphatase gene (phoD) and the phosphatase activity in rhizosphere and bulk soils under long-term gradient phosphorus (P) fertilization, aiming to reveal the microbial mechanism of P fertilization and rhizosphere effect in regulating soil organic P mineralization. [Methods] The calcareous soil of wheat-maize rotation system with long-term gradient P application in North China Plain was selected for the rhizobox experiments. We designed three P fertilization levels: 0, 50, and 200 kg P/hm² (P0, P50, and P200, respectively). The rhizosphere and bulk soils were collected 30 days after the sowing of maize seeds. High-throughput sequencing was carried out to analyze the phoD-harboring bacterial community, which helped reveal the effects of P gradient fertilization and rhizosphere effect on the community and network characteristics of phoD-harboring bacteria and their relationship with phosphatase activity. [Results] With the increase in P application, available P (AP) and alkaline phosphatase (ALP) activity increased significantly, which were significantly positively correlated with each other. Under P0 and P200 treatments, the abundance of phoD in the rhizosphere soil was significantly higher than that in the bulk soil. Under P50 treatment, the alpha diversity of the phoD-harboring bacterial community in the rhizosphere soil was significantly higher than that in the bulk soil. The redundancy analysis (RDA) showed that AP, organic P (Po), and total P (Pt) were the main factors affecting the phoD-harboring bacterial community. Compared with P0 treatment, P50 and P200 reduced the total nodes and edges and increased the robustness of the bacterial network in rhizosphere soil, while they increased the total nodes and edges and decreased the robustness of the bacterial network in the bulk soil. The Mantel test showed that the dominant taxa of phoD-harboring bacteria were significantly correlated with AP, acid phosphatase (ACP), cohesion, and network robustness in rhizosphere soil, while the correlations were not significant in the bulk soil. [Conclusion] P gradient fertilization and rhizosphere effect co-affected the abundance of phoD, alpha diversity, community structure, dominant taxa, network complexity, and stability of phoD-harboring bacteria, which further affected phosphatase activity and consequently regulated the mineralization of organic P.

Abstract:[Objective] A potential new actinomycete strain Agromyces sp. CS16 was isolated from the surface soil of the mangrove in Futian, Shenzhen. We studied the capacity and application of the strain in the removal of heavy metals from water, aiming to provide technical support for the bioremediation of heavy metal-polluted water. [Methods] The capacity of strain CS16 in removing Cd²⁺, Ni²⁺, Cu²⁺, and Zn²⁺, and the extracellular and intracellular removal rates of the metal ions were determined. Moreover, the whole genome sequencing was performed to identify the genes associated with the heavy metal tolerance in strain CS16. Furthermore, CS16 was embedded with sodium alginate and polyvinyl alcohol, and the capacities of CS16 to remove heavy metals after embedding were also determined.[Results] Agromyces sp. CS16 presented great metal removal capacity. For Cd²⁺, the strain showed the maximum removal capacity of 32.95 mg/g and the maximum removal rate of 83.71% with the initial Cd²⁺ concentration of 10 μg/mL. For Ni²⁺, Agromyces sp. CS16 presented the maximum removal capacity of 25.09 mg/g with the initial Ni²⁺ concentration of 75 μg/mL, and it presented the maximum removal rate of 70.27% with the initial Ni²⁺ concentration of 10 μg/mL. For Cu²⁺, CS16 had the maximum removal capacity of 30.69 mg/g with the initial Cu²⁺ concentration of 150 μg/mL and the maximun removal rate of 80.11% with the initial Cu²⁺ concentration of 30 μg/mL. For Zn²⁺, the strain had the maximum removal capacity of 39.29 mg/g with the initial Zn²⁺ concentration of 125 μg/mL and the maximun removal rate of 88.91% with the initial Zn²⁺ concentration of 25 μg/mL. A total of 3 744 genes were predicted in the whole genome of strain CS16, of which 37 genes were deduced to be associated with the resistance to Cd²⁺, Ni²⁺, Cu²⁺, and Zn²⁺. CS16 mainly removed heavy metals in water by adsorbing heavy metal ions on cell walls. The embedding with sodium alginate (SA) and polyvinyl alcohol (PVA) decreased the removal capacity of CS16 for Cd²⁺ and improved the removal capacities for Ni²⁺, Cu²⁺, and Zn²⁺. [Conclusion] Agromyces sp. CS16 is a new strain isolated from mangrove surface sediments, with great capacity in removing Cd²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ from water. We explored the metal removal mechanisms of the strain at both cellular and genetic levels. CS16 was embedded with sodium alginate and polyvinyl alcohol and the embedding product presented better removal capacity for Ni²⁺, Cu²⁺, and Zn²⁺. In summary, CS16 is an efficient microbial agent in bioremediation of heavy metal-polluted water. Moreover, the findings of this study provide a theoretical basis for deciphering the mechanism of removing heavy metal ions from water by microorganisms.

Abstract:[Objective] The dynamic changes of bacteria in the fermentation process of Pixian broad-bean paste were explored from the species, abundance, and number of bacteria. [Methods] The 16S rRNA gene sequencing was carried out to analyze the bacterial species and abundance at four fermentation stages of Pixian broad-bean paste, and qPCR was employed to determine the total number of bacteria at different fermentation stages. [Results] The bacteria in Pixian broad-bean paste showed a dynamically stable community at the initial fermentation process, high richness during the whole fermentation period, and increased diversity over fermentation time (Shannon index increased from 1.25 to 3.50). The number and diversity of bacteria were associated with the fermentation environment at the early fermentation stage, and the bacterial diversity varied at different fermentation stages. Pantoea was the dominant genus during the fermentation of dry pepper, accounting for 20%. During the fermentation of broad bean, Staphylococcus had the highest relative abundance, which reached 38%. The dominant genus was Lactobacillus at the fermentation stages of red oil broad bean and Pixian broad-bean paste, with the relative abundance of 27% and 62%, respectively. [Conclusion] The relatively abundant bacteria at the early fermentation stage might have a significant impact on the quality and yield of Pixian broad-bean paste.

Abstract:[Objective] Polyethylene terephthalate (PET) plastics are usually discarded as waste, which seriously harms the ecological health. Considering the lack of thermophilic PET-degrading bacteria, this study aims to obtain a thermophilic PET-degrading bacterium and decipher its degradation mechanism. [Methods] We collected waste PET bottles from hot springs in Tengchong City, Yunnan Province and then extracted the biofilms from their surfaces to investigate the microbial diversity. We screened the thermophilic bacteria that could grow with PET as a nutrient source and identified them based on 16S rRNA gene sequences. According to the colonization ability and growth curve, we screened out a strain with strong degrading ability and determined the optimal pH, temperature, and NaCl concentration for its growth. Further, we investigated the degrading effects of the strain on PET and its intermediates, (bis(hydroxyethyl) terephthalate (BHET) and mono(2-hydroxyethyl) terephthalate (MHET), by measuring the product yield and degradation rate. In addition, we evaluated the interaction between the degrading bacterium and PET by observing morphology of the PET surface and determining the viable count and esterase activity. [Results] The microbial diversity was low in the biofilms of waste PET bottles. We isolated 5 thermophilic bacterial strains that could grow with PET as a nutrient source from the biofilms. Strain JQ3 using PET as the sole carbon source showed the best growth, which was identified as Bacillus thermoamylovorans. Its optimal growth conditions were pH 7.0, 50, and 0.5% NaCl. Strain JQ3 degraded PET at a rate of 0.043 mg PET/d, and the yield of terephthalic acid (TPA) peaked at 45.2 mmol/L on the 7th day. Moreover, strain JQ3 exhibited significant degradation effects on PET intermediates, degrading 85.9% of BHET within 6 h and 50.1% of MHET within 60 h. Strain JQ3 formed biofilm on the PET surface by colonization, which caused cracking and peeling of the PET surface. [Conclusion] The thermophilic PET-degrading strain B. thermoamylovorans JQ3 can degrade PET and its intermediates at high temperature (60), which provides a new strategy for PET degradation.

Abstract:[Objective] This study analyzed the fungal community composition and the pathogenic fungal network characteristics in the fields with different tillage measures, aiming to provide a scientific basis for understanding the role of microorganisms in maintaining and improving agroecosystem stability. [Methods] We employed high-throughput sequencing to investigate the composition and diversity of fungal communities and the network of fungal pathogens in the rhizosphere and bulk soils under the moldboard plow tillage (MP) and conservation tillage (reduced tillage: RT; no-tillage: NT). [Results] Compared with NT, MP and RT significantly increased the total carbon (TC), total nitrogen (TN), and available potassium (AK) in both the rhizosphere and bulk soils. The rhizosphere effect on the changes of fungal communities was greater than the effect of tillage measure. The Shannon index of the fungi in the rhizosphere soil under RT treatment was higher than that under MP and NT treatments. NT and RT decreased the relative abundance of Fusarium and Alternaria in the rhizosphere soils. In addition, RT reduced the network complexity of pathogenic fungi, weakened the interactions between the pathogenic fungi and their associated taxa, and enhanced the network stability. [Conclusion] These findings indicate RT as an optimal practice can increase soil nutrients, stabilize microbial network structure, and alleviate the potential transmission of pathogens, which provides a new perspective for tillage application in Northeast China.

Abstract:[Objective] Propsilocerus akamusi is one of the most important insects in aquatic ecosystem, and its gut microbiota is closely related to individual growth and development, environmental adaptation, and other physiological processes. This study aimed to investigate the potential effects of antibiotic treatment on the structure and the function of gut microbiota in P. akamusi larvae. [Methods] The microbes in the gut content of P. akamusi larvae treated by rifampin were analyzed and compared by using the 16S rRNA amplicon sequencing, and the functional prediction of gut microbial genes was conducted by using Tax4Fun method. [Results] Rifampin altered the structure and the diversity of gut microbiota in P. akamusi larvae. After rifampin treatment, the relative abundance of the bacterial phylum Bacteroidota (P<0.05) and Deferribacterota (P<0.001) was up-regulated, while that of Proteobacteria and Firmicutes was down-regulated. At the genus level, treatment with rifampin resulted in a significant decrease in the relative abundance of Yersinia,Pseudomonas, and Desulfovibrio (P<0.05). At the same time, the co-occurrence network showed that the stability of the microbiota coupled with the correlation between bacterial species were significantly weakened after rifampin treatment. Additionally, the Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis predicted that genes in the gut microbiota of P. akamusi larvae were mostly involved in the genetic information processing, metabolism, and human disease. Rifampin significantly increased the expression level of genes involved in drug resistance, while decreased those participating in endocrine and metabolic disease function. [Conclusion] The above-mentioned results reveal the potential effects of rifampin on the structure and the function of the gut microbiota in P. akamusi larvae, which build a fundamental basis to further explore the essential roles of the gut microbiota in P. akamusi.

Abstract:[Objective] To explore the effect of soil tetracycline on the growth and development, rhizosphere microbes, and nutrients of soybean sprouts, and to lay a theoretical basis for evaluating the influence of antibiotic residue on vegetable cultivation and preventing and controlling antibiotic contamination in soil-vegetable system. [Methods] We simulated different levels of tetracycline (0, 25, 50 mg/kg) in soil and determined the tetracycline in soybean sprouts by high performance liquid chromatography (HPLC). The nutrients in soybean sprouts were measured with physicochemical methods and rhizosphere microbes were elucidated by high-throughput sequencing.[Results] Tetracycline accumulation in soybean sprouts rose with the increase in the level of tetracycline in soil, and the distribution followed the order of root>hypocotyl>cotyledon. Tetracycline residue in soil significantly inhibited the development and biomass of root and hypocotyl, vitamin C synthesis, and antioxidant activity of soybean sprouts, particularly the vitamin C synthesis. To be specific, on the fifth day of growth, vitamin C content in soybean sprouts cultivated in soil with 25 mg/kg and 50 mg/kg tetracycline was 41.35% and 49.80% lower than that of the control, respectively. Moreover, tetracycline residue significantly affected the microbial community structure in rhizosphere of soybean sprouts, especially the nitrogen cycling-related genera. Specifically, the relative abundance of Acinetobacter and Thermus significantly increased and that of Pseudoxanthomonas and Hydrogenophaga reduced. [Conclusion] Tetracycline residue in soil suppressed the growth of soybean sprouts, rhizosphere microbial community structure, and important nutrients such as vitamin C.

Abstract:[Objective] To explore the genotypic differences and potential probiotic properties of Lactiplantibacillus plantarum by using whole genome sequencing technology. [Methods] Based on the HiSeq and PacBio, this study sequenced the potential probiotic strains L. plantarum Eden-Star PC06 and L. plantarum Eden-Star PC108 with good evaluation of in vitro probiotic properties isolated from Sichuan multi-generation Paocai in the previous study. The relevant bioinformatics software was used to assemble the raw data and analyze the subsequent functional annotation, molecular evolution, strain safety, secondary metabolite synthesis gene clusters, and probiotic-related genes. [Results] The whole-genome information of two L. plantarum strains was obtained through gene assembly, and the genome sizes of L. plantarum Eden-Star PC06 and Eden-Star PC108 were 3 163 902 bp and 3 205 054 bp, respectively. The GC content of Eden-Star PC06 and Eden-Star PC108 was 44.68% and 44.67%, respectively, and they contained 3 161 and 3 197 DNA coding sequences, respectively. The comparison results of functional gene database showed that the two strains were extensively annotated on genes such as carbohydrate utilization, amino acid utilization, and glycosyltransferase. We found four genes related to intestinal fluid tolerance, intact gene clusters related to bacteriocin synthesis of L. plantarum, and probiotic genes resistant to multiple stresses on the whole genome of two strains of L. plantarum in the comparison database. [Conclusion] This study explores the genotypic differences and potential probiotic properties of two L. plantarum strains Eden-Star PC06 and Eden-Star PC108 at the gene level by whole-genome sequencing, and it has proved that L. plantarum Eden-Star PC06 and Eden-Star PC108 are potential probiotic strains with promising applications. This study is expected to provide a genetic basis for screening out excellent probiotic strains and evaluating their probiotic properties.

Abstract:[Objective] N-methylpyrrolidone (NMP) was used as an electron donor for denitrification to treat wastewater. [Methods] NMP and glucose as electron donors were respectively added into the simulated effluent from wastewater treatment plant for denitrification, during which they were compared for the removal of nitrates. The fate of nitrogen released during the denitrification was studied, and the released nitrogen was further treated. Furthermore, we submitted the sludge samples acclimated with NMP and glucose for high-throughput sequencing to investigate their mechanisms of denitrification. [Results] The NMP-acclimating sludge showed the nitrate-N removal rate 67% higher than the glucose-acclimating sludge. After 8 h of denitrification with NMP as the electron donor, the total nitrogen (TN) composed of residual nitrate N, generated nitrite N, and released ammonium N from NMP biodegradation was similar to the TN after the denitrification with glucose as the electron donor. [Conclusion] The wastewater containing NMP could be used as the electron donor for deep nitrate removal, although it was directly treated as the wastewater before. High-throughput sequencing indicated that NMP was different from glucose in the mechanism of denitrification when being used as the electron donor. As one of the nitrogen-containing heterocyclic compounds, NMP releases the electron donor for denitrification through the biodegradation of organic acids after the cleavage of NMP ring. However, glucose releases its electron donor for denitrification through the biodegradation without ring cleavage because of its simple structure. The results have theoretical significance for utilizing nitrogen-containing heterocyclic compounds as electron donors for denitrification.

Abstract:[Objective] Ubiquitins, a class of highly conserved 76-amino acid peptides, are essential substrate molecules in the ubiquitination of proteins. The abnormal ubiquitination of proteins is directly associated with the individual growth and development. The role of orf26, a gene encoding ubiquitin of silkworm baculovirus, in virus proliferation remains unclear. [Methods] The chloramphenicol gene (Cm) expression cassette was used to replace a 50 bp fragment at the 3′ end of the ubiquitin gene sequence by homologous recombination, and the recombinant Bombyx mori nucleopolyhedrovirus (BmNPV) carrying Cm expression cassette (Bm-Bacmid^Ub-KO) was constructed. A green fluorescent protein expression cassette was inserted into Bm-Bacmid^Ub-KO and Bm-Bacmid^WT via transposition for the construction of recombinant Bm-Bacmid^Ub-KO-GFP and Bm-Bacmid^WT-GFP, respectively. Meanwhile, the repair type of Bm-Bacmid^GFP-UbRep was constructed in the study. [Results] The deletion of ubiquitin gene did not affect the generation of infectious virions in BmN cells, while it decreased the production of progeny virions. Western blotting showcased that the deletion of ubiquitin gene down-regulated the expression levels of viral structural proteins GP64 and VP39, which were directly involved in the production of progeny virions. Furthermore, the bioassay results showed that the deletion of ubiquitin gene caused a 15-h delay in the median lethal time of silkworm. [Conclusion] The deletion of ubiquitin gene in BmNPV did not affect the production of infectious virions while significantly reducing the efficiency of viral proliferation. This study lays a foundation for clarifying the specific role of ubiquitin in BmNPV proliferation.