Abstract:Streptococcus pneumoniae is a Gram-positive extracellular bacterium colonized in the upper respiratory tract, and the main cause of invasive pneumonia with high morbidity and mortality. Inflammasomes are multi-protein complexes located in the cytosol and critical in innate immune responses. Numerous studies have shown that S. pneumoniae infection can induce the assembling of inflammasomes, activation of caspase-1 and secretion of pro-inflammatory cytokines. Under the long-term selection pressure, S. pneumoniae evolves with some mutations to escape inflammasome recognition. In this review, mechanisms on the interactions between S. pneumoniae and host inflammasomes, including the induction and active role of inflammasomes during S. pneumoniae infection, and the evasion strategy of S. pneumoniae against inflammasome recognition are summarized.

Abstract:Antibacterial drugs have played important roles in treating bacterial diarrhea in pet animals; however, with the increase of bacterial resistance, the therapeutic effect of antibacterial drugs has been severely reduced. Probiotics are defined as “live microorganisms conferring health benefit on the host”, and have the potential for preventing, treating and healing bacterial diarrhea in pet animals. The application of probiotics in treating bacterial diarrhea is grossly promising. The species of bacterial pathogens, characteristics and prevention and treatment of current situation of diarrhea in pet animals, as well as the species, screening requirements, mechanisms, existing problems and application prospect of probiotics ameliorating gastrointestinal diseases in pet animals are reviewed.

Abstract:Methanogens are a group of extremely anaerobic microorganisms affiliated with the archaeal domain. They use simple compounds such as carbon dioxide, acetate and methyl compounds as substrate to grow. Hydrogenotrophic methanogens is the main type in all the cultured species. Among the three major methanogenic pathways, the hydrogenotrophic methanogenesis shows the highest energy productivity and includes a special energy metabolism system. In recent years, with the development and application of mass spectrum, spectroscopy and crystallization technology, the research on the methanogenic pathway has been further studied, especially in the biochemical mechanism of hydrogenotrophic methanogenesis, which revealing a unique and efficient way of energy conversation under extreme environment. Based on the massive research results, this review summarizes the details of hydrogenotrophic methanogenesis from the aspects of energy storage, metabolic pathways, enzyme structures and catalytic mechanism of enzymatic reactions. The prospect for the future research and technological development in the field of methanogenesis is also proposed in this review.

Abstract:The latest research estimates that there are about 1.83 billion people living in anthrax risk areas in the world. After decades of development, the number of global anthrax research results is abundant and the total amount is increasing. [Objective] This paper analyzes the global anthrax research literature in order to obtain the evolution trend and hot spot change of its research field. [Methods] Based on Web of Science literature and scientific measurement methods, this paper analyzes the global anthrax research between 1998 and 2018 in a visual way, and comprehensively uses CiteSpace visual analysis software to analyze the evolution trend and hot spot changes in the global anthrax research field through some methods. [Results] Global anthrax research can be divided into three research stages: multi-dimensional outbreak between 1998 and 2004, continuous exploration between 2005 and 2013 and emerging hot spots between 2014 and 2018. [Conclusion] The rapid, real-time and trace detection of anthrax and new anthrax vaccine are likely to become the research hotspot of global anthrax in the future.

Abstract:[Objective] To understand the molecular mechanism of the effector nopP in the nodulation and nitrogen fixation of Sinorhizobium fredii SMH12, and to provide foundation for effective genetic improvement of rhizobium-soybean symbiosis, we studied the function of nopP in symbiotic nitrogen fixation between S. fredii SMH12 and soybean. [Methods] The phylogenetics of the NopP was analyzed by bioinformatics, and the deletion mutant (ΔnopP), overexpression (OE-nopP) and complementation strains (CM-nopP) were constructed by genetic operation. We further analyzed the symbiotic phenotypes. Meanwhile, the expression pattern of nopP under free-living and symbiotic conditions and the expression of NIN, ENOD40, PR1, PR2 and PR5 in ΔnopP mutant in roots of Glycine max cv. JD17 inoculated with SMH12 and SMH12 ΔnopP were detected by quantitative real-time PCR (qRT-PCR). The subcellular localization of NopP was observed by laser confocal microscopy. [Results] The NopP protein of S. fredii SMH12 does not contain any functional domains and has no homologues with Avr effectors in the genome of several pathogens. Deletion of nopP in SMH12 significantly increased the nitrogen fixation activity of JD 17 and Zhong Huang 13 compared with the wild type strain SMH12, and the nodule number significantly increased in JD17 inoculated with the mutant ΔnopP. It is indicated that the deletion of nopP promoted the symbiotic nitrogen fixation with JD17 or Zhong Huang 13. qRT-PCR showed that the expression level of nopP under symbiosis was significantly up-regulated compared to that under free-living condition, and the nopP was highly expressed at a 2-day post inoculation (dpi), indicating that the nopP gene plays important role in the rhizobia early infection and the symbiotic nitrogen fixation. In addition, the NopP protein localizes at the cytoplasm membrane and nucleus in both tobacco leaves and soybean roots. Moreover, the expression of NIN in the roots of JD17 inoculated with the mutant ΔnopP was up-regulated by 1.2 times, whereas the expression level of PR5 was down-regulated by 3.6 times compared to the wild-type SMH12 inoculation. [Conclusion] The effector protein NopP of SMH12 plays important roles in the early infection of rhizobia and the defense response regulation in soybean under symbiosis.

Abstract:[Objective] Twenty-nine healthy young volunteers from Hainan were selected as the research objects to analyze the diversity of gut microbes and to explore the effects of Lactobacillus paracasei subsp. paracasei Zhang on the fecal microbiota. [Methods] Volunteers were supplemented with 1×10¹⁰ CFU LCZ powders per day for 14 days. Fecal samples were collected on 0, 14 and 28 days. Microbial composition and structure of fecal were analyzed by PacBio SMRT. [Results] Firmicutes and Bacteroidetes were the most abundant phylum. Meanwhile, Bacteroides were the predominant genus. At the species level, the dominant bacteria species were Faecalibacterium prausnitzii, Eubacterium rectale and Prevotella copri. After taking LCZ for 14 days, the dominant bacteria did not change significantly, while low-abundance bacteria such as Oscillospira and Parabacteroides were significantly increased (P<0.05). In addition, volunteers were divided into two groups according to the changes of Lactobacillus. Butyricicoccus pullicaecorum, Lactococcus raffinolactis and Parabacteroides distasoni were significantly increased in samples of those with significantly increased content of Lactobacillus. Inversely, volunteers with no significant changes in the Lactobacillus content in their gut did not find similar changes. [Conclusion] Continuous consumption of probiotics LCZ for 2 weeks had no significant effect on the relative abundance of dominant bacteria in fecal microbiota of volunteers, while the low-abundance bacteria change significantly.

Abstract:[Objective] The predicted mechanism of indole-3-acetic acid (IAA) synthesis was investigated by molecular method on an endophytic bacterium Herbaspirillum aquaticum ZXN111 that was isolated from Zijuan tea. [Methods] Aromatic-amino-acid aminotransferase gene (tyrb) in indole-3-pyruvicacid (IPA) pathway responsible for IAA synthesis was selected on the basis of Herbaspirillum seropedicae genomic analytical results. Gene tyrb was mutated by recombinant plasmid pK19mobΩ2HMB-P-tyrb to produce mutant tyrb::pK19mobΩ2HMB, and a complementation strain tyrb::pK19mobΩ2HMB(+) was further constructed by recombinant plasmid pSRK-Gm-tyrb. IAA synthesis activities of mutant tyrb::pK19mobΩ2HMB, strain tyrb::pK19mobΩ2HMB(+) and wide type ZXN111 were analyzed, and the three strains' plant growth promotion (PGP) activity was evaluated by tissue cultured seedling of Yunkang-10. [Results] After tyrb gene mutated by pK19mobΩ2HMB-P-tyrb insertion, IAA synthetic activity of mutant tyrb::pK19mobΩ2HMB was much lower than that of wild-type ZXN111 in 48 h culture, but IAA synthesis activity of complementary strain tyrb::pK19mobΩ2HMB(+) was restored by plasmid pSRKGm-tyrb. The wide-type strain ZXN111 positively regulated the plant growth of Yunkang-10, while the mutant tyrb::pK19mobΩ2HMB lose the plant promotion activity significantly. [Conclusion] The indole-3-pyruvate (IPA) pathway is the primary IAA synthesis pathway in Herbaspirillum aquaticum ZXN111 and the tyrb is the key gene of IPA pathway, but other alternative pathways are also existed. Auxin production was one of the important contributors to PGP activity of Herbaspirillum aquaticum ZXN111.

Abstract:[Objective] By studying the effect of conversion of forest to arable land on the abundance, diversity and structure of soil alkaline phosphatase gene encoding bacterial community, to provide basic data of soil microbial diversity, for sustainable land use. [Methods] The abundance, diversity and structure of soil alkaline phosphatase gene encoding bacterial community were investigated using real-time fluorescence quantitative PCR (qPCR) and high-throughput sequencing. Combining the determination and statistical analysis of soil chemical properties, relationships among the soil alkaline phosphatase gene encoding bacterial community abundance, Shannon diversity and soil chemical properties were also evaluated, as well as the key driving factors affecting community structure. [Results] After the forest land was reclaimed as arable land, long-term fertilization led to acidification of the soil, the pH dropped from 5.58 to 4.72, and the soil available phosphorus increased from 2.49 mg/kg to 49.3 mg/kg. Correspondingly, the soil alkaline phosphatase gene encoding bacterial community abundance and diversity significantly decreased with the conversion of forest to arable land. Based on species classification of alkaline phosphatase-encoding gene sequence, Proteobacteria, Cyanobacteria, Planctomycetes, Actinobacteria, Firmicutes and Verrucomicrobia were the dominant phyla, and the relative abundance of Cyanobacteria in forest significantly higher than that in arable land. The relative abundance of Bradyrhizobium and Bacillus in arable land were significantly higher than that in forest, while significantly higher relative abundance of Mesorhizobium, Pseudomonas, Chlorogloea, Gemmata, Phormidesmis and Pseudolabrys was found in forest. The structure of soil alkaline phosphatase gene encoding bacterial community was significantly affected by the land-use change. The abundance and Shannon diversity of soil alkaline phosphatase gene encoding bacterial community were significantly positively correlated with pH, but significantly negatively correlated with the soil available phosphorus, total phosphorus, nitrate nitrogen (NO₃^-) and ammonium nitrogen (NH₄⁺), the soil available phosphorus is the most affected among these factors. The application of inorganic phosphate fertilizer caused the degradation of organophosphorus decomposition ability of soil bacterial community containing alkaline phosphatase. [Conclusion] The soil available phosphorus and pH changed by land-use change and long-term fertilization cause the alteration of the abundance, diversity and structure of the soil alkaline phosphatase gene encoding bacterial community under the coordinated driving of other physical and chemical factors.

Abstract:[Objective] The purpose of this study is to isolate and identify the high-efficient degradation strains of fenoxaprop ethyl, providing strain resources and theoretical basis for the development of degradation agents, enhancing the in-situ bioremediation of fenoxaprop ethyl residue contaminated soil, and ensuring the safety of cucumber products. [Methods] The degradation strain was isolated by enrichment culture method and identified by morphology, physiological, biochemical characteristics and 16S rRNA gene evolution analysis. Intermediate products during fenoxaprop ethyl degradation were analyzed by HPLC/MS. The key hydrolase gene was cloned by shotgun method, and heterologously expressed. Michaelis-Menten double reciprocal curve and orthogonal tests were used to determine the enzyme kinetic and liquid fermentation parameters of the degradation strain. Through the irrigation of degradation strain, the fenoxaprop ethyl degradation in cucumber rhizosphere soil and the enhancement effect of mannitol on degradation efficiency were studied. [Results] Rhodococcus sp. DSB-1 was able to transform 100 mg/L fenoxaprop ethyl to fenoxaprop acid as sole carbon source within 24 h. The optimum degradation temperature and pH were 30 ℃ and 8.0, respectively. A fenoxaprop ethyl hydrolase gene named pepE was cloned from the genome of strain DSB-1 by shotgun method. The K_m and k_cat/K_m of the hydrolase PepE towards fenoxaprop ethyl were 28.2 μmol/L and 11.0 L/(μmol·s). The degradation agent acquired possessed the highest degradation efficiency towards fenoxaprop ethyl under the fermentation conditions: temperature of 30 ℃, ventilation rate of 1:0.4, stirring speed of 200 r/min and culture time of 48 h. Strain DSB-1 could colonize on the cucumber root surface, and completely degraded 10 mg/kg fenoxaprop ethyl residue in cucumber rhizosphere soil within 12 d. Addition of mannitol could improve the degradation efficiency by 14.8% compared with the non-added treatment. [Conclusion] Strain DSB-1 could be potentially applied in bioremediation of fenoxaprop ethyl contaminated soil.

Abstract:[Objective] Vibrio parahaemolyticus is an important zoonotic pathogen. Its localization of lipoprotein (Lol) system is responsible for the transport and localization of lipoproteins in this bacterium, which is closely related to its pathogenicity and drug resistance. Systematic bioinformatics analysis of the Lol system transporters is helpful to promote further research on pathogenesis and resistance mechanism of V. parahaemolyticus. [Methods] The basic properties, protein interactions and tertiary structures of Lol system transporters LolA-E and LolCD₂E of V. parahaemolyticus were investigated by bioinformatics analysis, combining with ExPASy online tools, SignalP 4.0 Server, TMHMM-2.0, STRING, SWISS-MODEL and other softwares. [Results] LolA and LolB were acidic hydrophilic proteins with signal peptide sites and no transmembrane region, while LolC and LolE were alkaline hydrophobic membrane proteins. LolCD₂E was an neutral hydrophobic membrane protein, and LolC-E and LolCD₂E had no significant signal peptide sites. Subsequent studies should add a signal peptide sequence in the recombinant expression vector of LolCD₂E protein, and combine with detergent treatment to ensure the protein expression and purification. Protein interaction network showed that the coding genes of five proteins LolA-E can co-express, and be responsible for the synthesis and transport of lipoprotein. LolA-E had close interaction with other outer membrane proteins such as BamA, Pal, MacB and CmeC. Tertiary structural homology modeling showed that V. parahaemolyticus and Escherichia coli had the similar structures in LolA and LolB proteins. And LolC-E contained the homologous structure of MacB protein, which gave Lol system an important function for consuming ATP to transport lipoproteins. Furthermore, this study found a conserved Hook structure in LolC and LolE of V. parahaemolyticus for the first tim, which is a key region for LolCD₂E complex to bind with LolA and transport lipoprotein. [Conclusion] This study provides an important data basis for the study of expression purification, structure and function of Lol system transporter in V. parahaemolyticus, and provides new targets for the subsequent research and development of new antibacterials.

Abstract:[Objective] To elucidate the composition, spatial distribution and interaction between phytoplankton community and environmental factors in Hongchaojiang Reservoir. [Methods] The community structure and diversity of planktonic bacteria in Hongchaojiang Reservoir were analyzed based on the 16S rRNA gene high-throughput sequencing technology. The physical and chemical variables of the water were detected simultaneously. [Results] A total of 28 phyla, 79 classes, 168 order, 243 families, 325 genera and 85 species were identified. Proteobacteria, Actinobacteria, Cyanobacteria, Verrucomicrobia, Bacteroidetes and Planctomycetes accounted for 21.95%, 21.30%, 17.98%, 12.27%, 11.72% and 9.51%, respectively. The PCoA analysis based on bray-curtis distance showed that the nine sampling sites in Hongchaojiang Reservoir could be divided into three groups, with the bacterial community displaying a gradient change along the upstream and downstream. The perMANOVA test indicated significant differences among the groups. However, there was no significant difference of the diversity index among the groups. Mantel analysis further confirmed that the transparency (Trans), turbidity (Turb), total phosphorus (TP), nitrite nitrogen (NO₂N), nitrate nitrogen (NO₃N), chlorophyll a (Chlo), pH, dissolved oxygen (DO), oxidation reduction potential (ORP), specific conductivity (SPC), total dissolved solids (TDS), nutritional status (TLI) would affect the planktonic bacteria community structure significantly. [Conclusion] The spatial distribution of bacterioplankton in Hongchaojiang Reservoir is influenced by the combined effects of physical and chemical factors and agricultural activities. These results provided scientific references for understanding the spatial pattern of the plankton-bacterial community and its response to human activities as well as reservoir management.

Abstract:[Objective] The present work aims to screen cultivable microbes and bioactive metabolite producing bacteria in the gut of Sipunculus nudus from different areas of Beibu Gulf, so as to provide theoretical support for the subsequent development and utilization of gut microbial metabolites of Sipunculus nudus. [Methods] We isolated cultivable microbes from Zhanjiang, Beihai and Fangchenggang by plate and streak cultivation, and identified those microbes according to 16S rRNA gene sequence analyses. Meanwhile, we investigated the extracellular bioactive metabolites producing bacteria by transparent ring method, visible spectrophotometer and inhibition zone methods. [Results] We successfully screened 12 cultivable microbial genera from the gut of Sipunculus nudus in three Beibu Gulf regions, including Vibrio, Shewanella, Pseudomonas, Photobacterium, Bacillus. Vibrio is the dominant bacterium among the three regions. The strains producing extracellular protease, chitosanase, polysaccharide and bacteriostatic activity were mainly from Pseudomonas, Photobacterium, Bacillus. [Conclusion] There are significant differences on the bacteria genus level among the gut of Sipunculus nudus from different area of Beibu Gulf in China. Meanwhile, the cultivable symbiotic microorganisms of Sipunculus nudus can produce various extracellular active substances, which indicated that Sipunculus nudus is a good source of marine bioactive metabolites.

Abstract:L-arginine is a semi-essential amino acid that is widely used in food, pharmacy and feed industries. In recent years, the metabolic engineering of L-arginine producing strains is rarely involved in the field of ion transport. [Objective] In this study, we found that adding appropriate K⁺ in the medium was beneficial to Corynebacterium crenatum SYPA5-5 to increase L-arginine production. [Methods] Transcriptome of C. crenatum SYPA5-5 was analyzed under the concentrations of 0.5 g/L and 2.5 g/L K₃PO₄. We selected significant monovalent cation/H⁺ antiporter Mrp1A and cation transport ATPase CTAP1 to investigate the relation among K⁺ transport, growth and L-arginine synthesis in C. crenatum SYPA5-5. [Results] The genes mrp1 and ctap1 were deleted and overexpressed to analyze their effects on the production of L-arginine in C. crenatum SYPA5-5. The overexpression of Mrp1A and CTAP1 was beneficial to ion homeostasis, pH tolerance and osmoregulation, ultimately increasing L-arginine production. In fed-batch fermentation, L-arginine production of 5-5(mrp1), 5-5(ctap1) and 5-5(mrp1ctap1) strains reached 61.4 g/L, 63.9 g/L and 65.3 g/L. The yield reached 0.383, 0.392 and 0.395 g/g, which were 34.9%, 38.0% and 39.1% increase compared with C. crenatum SYPA5-5, respectively. [Conclusions] The CTAP1 is K⁺ transporter that can transport K⁺ from extracellular to intracellular. Meanwhile, the Mrp1A can transport K⁺ and Na⁺ to the extracellular, and the extracellular H⁺ was transported into the cell, thus maintaining the intracellular pH stability. The study of Mrp1A and CTAP1 provide a foundation for understanding the relationship between ion transport mechanisms and L-arginine synthesis.

Abstract:[Objective] Ascosphaera apis exclusively infects honeybee larvae, leading to chalkbrood, a fungal disease damaging honeybee health and beekeeping industry. The objective of this study was to investigate the differential expression pattern of circular RNAs (circRNAs) and differentially expressed circRNAs (DEcircRNAs) involved in Apis cerana cerana 6-day-old larval response to Ascosphaera apis stress, and the putative role of DEcircRNAs in host A. apis-response. [Methods] Normal and A. apis-infected 6-day-old larval guts of A. c. cerana (AcCK and AcT) were sequenced using linear RNA-removed circRNA-seq technology. CircRNAs were identified using find_circ software, followed by summary of length and circulization type of circRNAs. DEcircRNAs were screened out following the standard of |log₂(Fold change)|≥1 and P≤0.05. Source genes of DEcircRNAs were annotated to Gene Ontology (Go) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases to gain function and pathway annotations. RT-qPCR was conducted to validate three randomly selected DEcircRNAs. [Results] Based on circRNA-seq, 76342570 and 68269362 raw reads were produced from AcCK and AcT, and 74524108 and 66974392 clean reads were obtained after strict quality control, with Q30 of 92.75% and 94% and GC content of 54.31% and 54.90%. In total, 23648400 anchor reads were mapped to the reference genome of Apis cerana. In AcCK and AcT, 805 and 702 circRNAs were identified; the lengths of these circRNAs were distributed among 201-1000 nt, and the most abundant circulization type was annotated exonic circRNA; however, the numbers of circRNAs distributed in various lengths and circulization types were different. There were 494 DEcircRNAs in AcCK vs AcT comparison group, including 257 up-regulated circRNAs and 237 down-regulated circRNAs, with novel_circ_000123 and novel_circ_000726 having the highest up-regulation and down-regulation levels. Source genes of the aforementioned DEcircRNAs were annotated to 11 biological process-associated terms, nine molecular function-associated terms, nine cellular component-associated terms, and 73 pathways. Further analysis demonstrated partial source genes were engaged in seven cellular immune pathways and three humoral immune pathways. [Conclusion] A. c. cerana 6-day-old larvae may response to A. apis stress by altering the numbers of circRNAs distributed in various lengths and circulization types, specifically expressing some circRNAs, and regulating the expression of partial circRNAs; several DEcircRNAs such as novel_circ_000027, novel_circ_000127 and novel_circ_000312 may play special roles in host A. apis-response via regulation of oxidative phosphorylation, cellular and humoral immune pathways. Our findings offered novel insights into further understanding molecular mechanisms underlying A. c. cerana larval response to A. apis and host-pathogen interaction.

Abstract:Gallibacterium anatis is a conditional pathogen common in poultry production, and causes the laying hen genital tract diseases, resulting in decreased egg production. [Objective] To understand the biological characteristics and pathogenicity of the virulence factor RTX-like toxin GtxA and outer membrane protein W of G. anatis. [Methods] Based on the G. anatis OmpW gene deletion strain, we successfully constructed the OmpWgtxA double gene deletion strain by natural transformation. The differences in biological characteristics and virulence between single and double gene deletion strains and parental strain were investigated. [Results] The hemolytic activity of the OmpWgtxA double gene deletion strain was inactivated, while the deletion was stable in vitro and in vivo. Compared with gtxA, ompW single gene deletion strain and parental strain Yu-PDS-RZ-1-SLG, the growth of the double gene deletion strain was not significantly altered, while its adhesion ability and lesions of primary chicken oviduct epithelial cells were decreased to some extent; and its ability to induce apoptosis in cells of chicken oviduct epithelium was lessened; its pathogenicity was also reduced. [Conclusion] GtxA toxin and outer membrane protein W were suggested to play important roles in G. anatis virulence, adhesion to host cells and induction of apoptosis and there may be synergies. This study laid the foundation for further revealing the pathogenesis of G. anatis.

Abstract:[Objective] In this study, we analyzed the roles of PII signal transduction protein GlnK in nitrogen metabolism regulation and L-arginine biosynthesis in Corynebacterium crenatum. [Methods] The glnK overexpressed, glnK deletion and glnK knock-down strains were constructed. RT-qPCR and determination of enzyme activities were carried out to reveal the effects of GlnK on the expression levels and enzyme activities of nitrogen metabolism-related and L-arginine biosynthesis-related genes and enzymes. The changes of various parameters during the fermentation of recombinant strains were also investigated. [Results] Overexpression of GlnK protein had a significant effect on the absorption of NH₄⁺. The expression levels and enzyme activities of nitrogen metabolism-related and L-arginine biosynthesis-related genes and proteins have generally been up-regulated in Cc-glnK strain. Among them, genes encoding ammonium absorption-related enzymes, such as glnA, gltD and gdh, were significantly up-regulated with an average increase about 4.58 times. The L-arginine yield and productivity of Cc-glnK reached 49.53 g/L and 0.516 g/(L·h), respectively, at the end of fermentation. [Conclusion] Overexpression of GlnK could promote the absorption of NH₄⁺, increase the expression levels of genes and enzymes activities on the L-arginine biosynthesis pathway, ultimately increase the yield of L-arginine. It provided guidance for the subsequent exploration of the nitrogen regulation mechanism and metabolic modification of C. crenatum in the production of nitrogen-containing compounds.

Abstract:[Objective] Few studies have been reported about the biological control of plant parasitic nematodes by Microbacterium maritypicum. The purpose of this study was to determine the nematicidal activity of M. maritypicum Sneb159. In addition, nematicidal active compounds were separated from the culture supernatant of strain Sneb159. The study will provide fundamental knowledge about the development of biological pesticides. [Methods] We evaluated the direct antagonism to the second-stage juveniles (J2s) of Heterodera glycines in vitro. The nematicidal compound was separated and purified from culture supernatant of strain Sneb159 using organic solvent extraction, followed by silica gel chromatography and semi preparative high performance liquid chromatography according to the mortality of J2s. We characterized the compound by nuclear magnetic resonance spectrum. [Results] Strain Sneb159 showed strong nematicidal activity. The mortality of H. glycines J2s in Sneb159 treatment was significantly higher than that in the control after 24 h and 48 h incubation. One active compound, phenylacetamide, was obtained from culture supernatant of strain Sneb159. [Conclusion] To our knowledge, this is the first report to describe the nematicidal activity of M. maritypicum against H. glycines. The results suggested that strain Sneb159 and phenylacetamide have potential applications for biological control of H. glycines.

Abstract:[Objective] Trichoderma is a genus of common filamentous fungi used for biological control, by producing a variety of secondary metabolites that play an important role in biological control. In this study, a putative nonribosomal peptide synthetase (NRPS) NRPS1 was identified in Trichoderma hypoxylon by genome mining approach and the function of this gene's function was studied by using NRPS1 mutant against the pathogens. [Methods] Bioinformatics analysis reveals a putative NRPS containing biosynthetic gene cluster that is potential for the biosynthesis of peptaibol. The deletion cassette containing the hygromycin resistance gene was constructed by Quick-change method. The partial gene was deleted by using PEG mediated transformation in T. hypoxylon. NRPS1's function was identified by the biological activity assay against pathogenic fungi. [Results] We identified a putative peptaibol synthesis gene NRPS1 and obtained three deletion mutants. Deletion of NRPS1 significantly decreased the ability to resistance the pathogenic fungi, such as Aspergillus parasiticus, Fusarium oxysporum, and Verticillium alboatrum. [Conclusion] NRPS1 is a potential peptaibol synthesis gene in T. hypoxylon and plays important roles in the resistance to pathogenic fungi. This work lays the foundation for the elucidation of peptaibol biosynthesis and its application for the biological control in agriculture.

Abstract:c-di-GMP is a widespread second messenger in bacteria and regulates many important bacterial biological characteristics (such as biofilm, motility and virulence) by binding effector proteins. YeaI protein containing EGEVF motifs can bind c-di-GMP and may regulate bacterial performance. [Objective] To study the roles of yeaI in Escherichia coli NJ17 strain. [Methods] The yeaI mutant (NJ17ΔyeaI) and complementary strain (cNJ17ΔyeaI) were constructed. Growth characteristics, biofilm formation ability, adhesion and other biological characteristics were analyzed in NJ17, NJ17ΔyeaI and cNJ17ΔyeaI. [Results] We successfully constructed NJ17ΔyeaI and cNJ17ΔyeaI. Compared with NJ17, there was no significant changes in growth characteristics and drug resistance of NJ17ΔyeaI (P>0.05). However, biofilm formation ability of NJ17ΔyeaI significantly decreased and motility of NJ17ΔyeaI significantly improved (P<0.05). Transmission electron micrographs shows that yeaI deletion affected the formation of NJ17 fimbriae and flagella. qPCR results also showthat the yeaI gene significantly inhibited the transcription level of the flagella-related genes motB and filG in NJ17. Furthermore, serum survival experiments results show that deletion of yeaI significantly enhanced survival abilities of NJ17 in rat serum (P<0.05). However, compared with NJ17, there was no significant change in adhesion rate of yeaI mutant to EpH₄-Ev (P<0.05). [Conclusion] The yeaI plays an important role in regulating the biological characteristics of E. coli of cattle origin.