Abstract:Abstract: SXT/R391 family has the most abundant types and members in integrating conjugative elements (ICE)．SXT/R391 elements are comprised of conservative core genes and genes in variable regions．The functions of conservative core genes of SXT/R391 include integration and excision，self-transfer through conjugation，and regulation of its expression．The genes in the variable regions often encode for drug and heavy metal resistances，forming of biofilm，adjustment of bacterial motility，and toxin-antitoxin systems that prevent SXT/R391 deletion from hosts．Some genes in variable region of SXT/R391 also encode for restriction-modification system，helicase，and endonuclease．The activity of SXT/R391is positively regulated by activator SetCD，and negatively regulated by repressor SetR．SXT/R391 cannot be easily deleted from the primary donors in the process of transfer．SXT/R391 prevent the acquirement of closely related and homogeneous elements but cannot prevent the acquirement of heterogenetic ICE，which leads to the generation of hybrid ICE under the action of recombination system encoded by SXT/R391 themselves．SXT/R391 have high transferable frequency and wide host range，and until now more than 40 different SXT/R391 elements have been discovered in various bacteria，especially in Vibrio species，which mainly distribute in coastal areas in Asia and Africa．It suggests that marine environments are likely the main reservoir for SXT /Ｒ391 and these elements probably spread from marine environmental strains to clinical strains，under increasing selective pressure．Due to the hazard caused by the prevalence and the transfer of SXT/R391，medical microbiologist and health departments should be fully alert to the spread of the elements.

Abstract:Abstract: The large numbers of microorganisms that inhabit mammalian gastro-intestine have a highly coevolved relationship with the host’s health in nutrition，immunity and other aspects．There is a complex relationship between microbiota and immune system．Although they can inhibit the pathogens invade epithelial tissue，many of these microbes have functions that are critical for stimulating host intestinal immune cells such as Tregs cells，Th17 cells differentiation．However，the disorder of the intestinal flora can cause bacterial translocation， intestinal barrier dysfunction．The mammalian immune system plays an essential role in maintaining homeostasis with resident microbial communities，though secreting a variety of immune effector cytokines such as MUC，sIgA，ITF，ＲegIIIγ，and α-defensins．Here，we review the composition of intestinal flora on simple stomach animal and the interactions between resident microbes and the immune function．

Abstract:Abstract: Most members of the Burkholderia cepacia complex (Bcc) are important human opportunistic pathogens．Although progress has been achieved on the taxonomy and molecular identification of these bacteria，the molecular mechanisms of Bcc pathogenicity remain unclear and little development is made for new therapeutic agents．As Bcc is resistant to many common clinically-relevant antibiotics，revealing its virulence determinants is therefore very important to develop novel antibiotics or alternative anti-infective therapies．In this review，we summarize current advances in principal virulence determinants，limitations and genetic tools for studies of pathogenesis of Bcc．We primarily focus on key pathogenicity factors，including innate resistance to antibiotics，protein secretion system，and quorum-sensing systems．

Abstract:Abstract: ［Objective］ We analyzed the symbiotic efficiency and genetic diversity of rhizobia isolated from Leucaena leucocephala in Liangshan Prefecture of SichuanProvince．［Methods］We studied genetic diversity of these isolates with 16S rRNA ＲFLP，BOX-PCＲ and AFLP fingerprinting，and constructed phylogenetic tree based on the concatenated sequences of the four housekeeping genes 16S rRNA，recA，atpD and glnII．The nodulation ability and the symbiotic efficiency of the isolates were tested by plant inoculation assay on their original host plant．［Results］ Genetic diversity and phylogenetic tree indicate that 26 isolates were assigned as Sinorhizobium，3 Bradyrhizobium，3 Rhizobium and 1 Mesorhizobium．SCAU203 might represent a new Ｒhizobium group，SCAU211 might represent a new Bradyrhizobium group，the other three representative strains were located in three phylogenic branches and closely related to S.americanum，M．plurifarium and R.huautlense，respectively．In the nodulation and symbiotic efficiency assay，only 2 of the 20 isolates promoted the growth of L．leucocephala，but 3 isolates had a growth slowing effect on the host，while the other isolates (84%) were ineffective on symbiotic nitrogen fixation．［Conclusion］The majority of rhizobia isolated from L.leucocephala in Liangshan Prefecture were ineffective on symbiotic nitrogen fixation.

Abstract:Abstract: ［Objective］ To produce human glycoproteins in Saccharomyces cerevisiae，human N-glycosylation pathway must be genetically engineered into the yeast cell．We tried to construct a strain，which can be used to introduce human Nglycosylation reactions，by disrupting several special glycosyltransferases in yeast N-glycosylation pathway．Furthermore，this mutant cell was applied for adaptive evolution to overcome its growth-defect phenotype．［Methods］Three yeast genes ALG3，OCH1 and MNN1 were disrupted． The N-linked oligosaccharides from the mutant cells were analyzed by the activity staining of invertase，and their structure was further confirmed by high-performance liquid chromatography (HPLC) and the treatment with glycosidase．Mutant cells were cultured under a high temperature for their adaptive evolution of growth．［Results ＆ Conclusion］We obtained a Δoch1Δalg3Δmnn1 strain that produces Man5GlcNAc2 intermediate of human Nglycosylation．Our approach for adaptive evolution resulted a remarkable improvement on the growth phenotype of Δoch1Δalg3Δmnn1 strain． In addition，we also confirmed a small amount of unexpected Man6GlcNAc2 intermediate from Δoch1Δalg3Δmnn1 strain．Treatment with α-1，2-mannosidase converted both Man5GlcNAc2 and Man6GlcNAc2 products to a single Man3GlcNAc2 form，indicating that the additional mannose on Man6GlcNAc2 product comes from an α-1，2 modification．Our results demonstrate that Δoch1Δalg3Δmnn1 triple mutant can be used as an initial strain to construct an yeast therapeutic glycoprotein-expression system by introducing various enzymes that are involved in human N-glycosylation pathway.

Abstract:Abstract: ［Objective］ To study the effect of temperature on prodigiosin synthesis in Serratia marcecens JNB5-1．［Methods］Different proteins obtained after culturing S．marcecens JNB5-1at 28 ℃ and 37 ℃ were separated and identified through two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization-time of flight-mass spectrometry．Subsequently，7 of the proteins were further analyzed by real-time qPCR．［Ｒesults］ We identified 16 different proteins． Among them，prodigiosin biosynthetic enzymes (O-methyl transferase and Oxidoreductase) and proteins related with the precursor substances (proine，methionine，serine，2-Octenal and Malonyl-CoA) of the prodigiosin biosynthetic were significantly down-expressed at 37℃．Heat shock protein (Hsp60) and superoxide dismutase were upexpressed at 37 ℃．The results of real-time qPCR show that the mRNA transcriptional levels of o-methyl transferase，oxidoreductase and transketolase at 37 ℃ were all lower than that at 28 ℃．［Conclusion］ S.marcecens JNB5-1 could produce prodigiosin at lower temperature (28℃) but not at higher temperature (37 ℃)．Higher temperature probably inhibited the expression of enzymes related with prodigiosin biosynthesis.

Abstract:Abstract: ［Objective］ To study the regulation mechanism of biofilm formation c-di-GMP synthesisby AphA in Vibrio parahaemolyticus，by using phenotypic and molecular biochemical experiments．［Methods］ Colony morphology and crystal violet staining assays were used to analyze the phenotypic changes between the aphA null mutant (ΔaphA) and the wide-type (WT) parent strain． The intracellular levels of c-di-GMP in the ΔaphA and WT strains were determined by a chromatography-coupled tandem mass spectrometry (HPLC-MS /MS) method． Total ＲNAs were extracted from ΔaphA and WT．Quantitative ＲT-PCＲ was applied to calculate the transcriptional variation of scrABC and scrG between ΔaphA and WT．The promoter-proximal regions of scrABC and scrG were cloned into the pHＲP309 vector containing a promoterless lacZ gene，respectively．Then，each of the two recombinant LacZ reporter plasmids was transformed into ΔaphA and WT，respectively，to measure the promoter activity (the β-Galactosidase activity) of the target genes in ΔaphA and WT by using the β-Galactosidase Enzyme Assay System．The over-expressed His-AphA was purified under native conditions with nickel loaded HiTrap Chelating Sepharose columns (Amersham)．Then，the electrophoretic mobility shift assay (EMSA) was applied to analyze the DNA-binding activity of His-AphA to scrABC and scrG promoter regions in vitro.［Ｒesults］ The phenotypic experiments disclosed that AphA was an activator of c-di-GMP synthesis and biofilm formation in Vibrio parahaemolyticus．The quantitative ＲT-PCＲ and LacZ fusion results showed that the transcription of scrABC and scrG was under negative control of AphA．However，the purified His-AphA could not bind to the upstream DNA regions of scrABC and scrG，as determined by EMSA．［Conclusion］The fact that AphA represses the transcription of scrABC and scrG will at least partially account for the positive regulation of c-di-GMP synthesis and biofilm formation by AphA in Vibrio parahaemolyticus．

Abstract:Abstract: ［Objective］We isolated Myxobacteria strains from soil samples collected from Guangzhou，identified the strain and studied the antitumor activity．［Methods］We isolated Myxobacteria strains from soil samples through inactivated E.coli inducing method， identified the strain according to morphological observation，physiological and biochemical characteristics，and the homologous analysis of 16S rＲNA sequences of nucleotides．The antitumor spectrum and the corresponding IC50 of the active component separated from the culture was analyzed．Confocal laser scanning microscope was used to examine the growth inhibitory effect of the active component on B16 cells．［Ｒesults］ We isolated a Myxobacteria strain and identified as Myxococcus macrosporus STXZ54．The active component termed SGF5 showed cytostatic activity against B16，Hela，4T1，Hep-3B with IC50 values of 10 μg/mL，and HCT-116 cell with IC50 values of 70 μg/mL．Subcellular structure of B16 cells were abnormal observed by confocal laser scanning microscope．Combining the apoptosis and necrosis assay result it is likely that SGF5 can induce apoptosis of B16 cells.［Conclusion］The active component separated from the culture of Myxococcus macrosporus STXZ54 has a significant antitumor activity tested by cytotoxicity assay，which was worth exploiting as potential antitumor drugs.

Abstract:Abstract: ［Objective］To identify and characterize a marine bacterial strain producing agarase．［Methods］The agaraseproducing bacterium was isolated from coastal sediments in Xiamen using agar as the sole carbon source．The strain was identified by the analyses of 16S rＲNA gene sequence，phenotype and biochemical reactions．Agarase activity was determined by dinitrosalicylic acid method，and the category of agarase was assayed using chromogenic substrate．At last，the characteristics of agarase were determined．［Results］ The results of the 16S rRNA phylogenetic，phenotypic and biochemical analyses showed that: the agar-degrading bacterium NTa belonged to the genus Stenotrophomonas sp. The strain could produce extracellular agarases，including α-agarase and β-agarase．The optimum temperature and pH of strain NTa agarase were 40℃ and 7.0，respectively．The enzymatic activity was stable below 30℃．It also showed stability over a pH range between 7.0 and．0.Ca2+ could activate agarase activity，and Na+，K+ and Mg2+ had no significant influence．However，Ag+，Ba2+，Fe2+，Mn2+，Cu2+，Zn2+ and Fe3+ inhibited the enzyme activity．The enzymatic activity of stain NTa agarase was inhibited by EDTA．The agarase had good resistance to some inhibitors，detergents and denaturant.［Conclusion］ Stenotrophomonas sp. NTa is a new type of agarase-producing strain，which can produce both α-agarase and β-agarase and has potential applications in the production of agaro-oligosaccharide．

Abstract:Abstract: ［Objective］We studied species diversity and enzyme activities of fungi from 11 marine sediment samples in the South China Sea.［Methods］ Salt-tolerant fungi were isolated by a dilution-plate method，and their diversity was studied based on fungal morphology and rDNA ITS (Internal Transcribed Spacer) sequences. Enzyme activities were screened by six special selective media.［Ｒesults］ A total of 1689 strains of salt-tolerant fungi were isolated．Morphology and ITS sequence analysis identified these fungi to 41 species of 15 described genera，of which Aspergillus sp．and Penicillium sp．were the dominant populations． Studies on enzyme activities of 41 sequenced strains showed that 8 strains produce cellulase，9 strains produce amylase，5 strains produce compound enzyme，16 strains produce protease，3 strains produce lipase and no strain produce chitonsanase．Acrodontium sp．8m and Aspergillus sp．86b produced the most multiple enzymes，while Penicillium sp．41m produced comparatively higher protease．［Conclusion］ There were abundant salttolerant fungi from marine sediment samples in the South China Sea，and more strains had enzyme activities.

Abstract:Abstract: ［Objective］ We studied the microbial interaction between anaerobic fungi and methanogens in the rumen of Holstein Cow.［Methods］ Co-cultures of anaerobic fungi with indigenously associated methanogen were isolated by Hungate roll-tube technique. The anaerobic fungi were identified by morphology and 4’，6 diamidino-2-phylindole nucleus staining and the methanogens were identified by 16S rＲNA gene sequencing． ［Ｒesults］A total of 28 co-cultures of anaerobic fungus with indigenously associated methanogen were obtained． The anaerobic fungi in the co-cultures were identified as monocentric genera Piromyces，Neocallimastix and Caeomyces. The indigenously associated methanogens were Methanobrevibacter olleyae like and Methanobrevibacter thaueri like strains．Four different phylotypes of fungus-methanogen co-cultures were obtained， which were Piromyces/Methanobrevibacter olleyae like strains，Neocallimastix/Methanobrevibacter olleyae like strains， Neocallimastix /Methanobrevibacter thaueri like strains and Caecomyces/Methanobrevibacter olleyae like strains．［Conclusion］Our study isolated and identified 28 co-cultures of anaerobic fungus and associated methanogens，which provided new materials for further study the mechanism of methane emission in the rumen．

Abstract:Abstract: ［Objective］ The characteristics of microscopic distribution and content of Undifilum oxytropis were observed and quantified in different tissues of Oxytropis glabra and Astragalus variabilis from natural grasslands of Inner Mongolia and Ningxia Province.［Methods］ Distribution of fungal endophyte was obtained in all the tissues (stems，leaves，seeds and roots) of O. glabra and A. variabilis though paraffin section and staining method of lactic acid phenol cotton blue;and content of fungal endophyte was determined though Ｒeal time-qPCR．［Results］ Endophytc fungi were observed mainly within the gap between the palisade tissue and parenchymatous tissue of seed coat in seed，mainly colonized in the superficial cells layer near stoma in the leaves，and in pith of stem mainly plants in the parenchymatous tissue around the edge of the vertical axis of the vascular bundle. There was an obviously difference in concentration of U. oxytropis in the plants collected in different locations．The content of U. oxytropis was highest in all seeds of O. glabra，while it was opposite in stems and leaves of two sampling points. Similarly，the content of U. oxytropis was highest in seeds，it was lowest in roots，and stems and leaves were opposite in A． variabilis from two sampling points. The detection limit was 0.029 pg/ng total DNA by Real time-qPCR.［Conclusion］When endophytic fungi infected the tissues of plants，there was selectivity to the tissues and cell type of host，and the colonization and distribution were influenced by habitats in fungal endophytes of locoweeds．

Abstract:Abstract: ［Objective］Marine bacteria are a rich source of potentially useful antimicrobial molecules. The purpose of the study is to explore the diversity of bacteria with antimicrobial activity isolated from Siganus fuscescens gastrointestinal tract collected from Naozhou Island (20°52'N－20°56'N 110°33'E－110°38'E)，Leizhou Bay，South China Sea.［Methods］We isolated bacteria from the gastrointestinal tract of fish sample using classical culturing technique，and determined antimicrobial activities of the isolates by Oxford cup method．We investigated diversity of antimicrobial isolates using phylogenetic comparative analysis of 16S rRNA gene sequences．［Results］According to the results of morphological observation and part of physiological and biochemical experiments，we isolated 68 strains from fish gastrointestinal tract． Among them，19 strains with antimicrobial activities were acquired (27.9% of the isolates) and represented 19 different species，belonging to 12 genera (Ｒothia，Micrococcu，Brachybacterium，Brevibacterium，Psychrobacter，Paracoccus，Cobetia，Citrobacter，Pseudomonas，Bacillus， Lactobacillus and Staphylococcus) of 11 families (Microbacteriaceae，Dermabacteraceae， Brevibacteriaceae，Moraxellaceae，Rhodobacteraceae， Halomonadaceae，Enterobacteriaceae，Pseudomonadaceae，Bacillaceae，Lactobacillaceae and Staphylococcaceae) in three phyla (Actinobacteria，Proteobacteria and Firmicutes)．Eight strains (42.1%)，7 strains (36.8%) and 4 strains (21.1%) were belonging to the phylum Firmicutes，Proteobacteria and Actinobacteria，respectively. The phylogenetic distance matrix results suggested that there were obvious genetic divergences between the majority of strains with antimicrobial activity and their phylogenetically most closely related typical strain，due to 16S rRNA gene sequences similarities ranging from 96.2 to 99.9%．In addition，4 strains (ZJHD2-31，ZJHD5-23，ZJHD2-58 and M26) could represent potential new species，and identification of the novel strain M26 has been published in Antonie van Leeuwenhoek.［Conclusion］ There are abundant diversity for bacteria with antimicrobial activity and potentially more new species of microorganism in Siganus fuscescens gastrointestinal tract collected from Naozhou Island.

Abstract:Abstract: ［Objective］ The mechanisms of nematophagous bacteria against nematodes remain unclear，limiting the use of biocontrol bacteria in the agriculture． Therefore，we constructed a rapid and efficient screening model to quickly identify new candidate genes involved in nematode infection.［Methods］ The wild-type Bacillus amyloliquefaciens FZB42 as well as more than 400 random mutants were inoculated into 5 mL liquid bioassay medium． After growth at 37℃ for 24 h，200 μL bacterial culture and 50－60 Level 4 age nematodes were added to 24-well plates，and then the survival rates of nematodes were determined at different time points．Through several rescreening，we selected the mutant strains whose nematicidal activities significantly decreased compared with the wild-type strain．Meanwhile，the conventional bioassay of solid plate was used as control.［Ｒesults］ Two mutants (F1 and F2) with obvious decreased nematicidal activities were selected from the random mutation library by liquid bioassay，consistent with the result of conventional solid plate bioassay. By comparing to 168 h-screening in each round of the solid plate bioassay，the method of liquid bioassay required only 24 h． The result indicated that the liquid bioassay greatly reduced the experimental time.［Conclusion］Our current study has successfully constructed a rapid and efficient method to bioassay the nematicidal activity，which could also lay the foundation for further cloning the candidate genes involved in the microbial infection against nematodes.