Abstract:Abstract:ε-poly-L-lysine (ε-PL) is a natural biomaterial that is biodegradable，edible and non-toxic toward humans and the environment． Based on the research history of ε-PL，we reviewed the biosynthesis，degradation and the metabolic pathway of ε-PL． We also addressed the status of ε-PL research in China.

Abstract:Abstract:In the battle to phages，bacteria have evolved many immune mechanisms involved in the prevention of phage DNA entry，the degradation of entered DNA，and the limitation of the phage spreading at the cost of host cell death. An immune system in bacteria is formed by the collaboration of multiple immune mechanisms． In this paper，we reviewed the latest research progress of bacterial immune system and focused on the analysis of the operation mode of bacterial immune system and the evolution relationship between this system and phages．

Abstract:Abstract:Shellfish is one of important vehicles for dissemination of food-borne pathogens． The incidence of food-borne diseases increases every year． Therefore，monitoring and control on the food safety of shellfish is a significant public health concern worldwide． In recent years，our group has studied the pathogens in molecular detection，bioaccumulation and control in shellfish． Based on the our previous studies，the purpose of this article was to provide a review on the pathogens in shellfish in four aspects: the detection methods，distribution，depuration and epidemiology． The molecular methods were widely used in detection of pathogens in shellfish． In addition，the pathogens were bio-accumulated in the gills and digestive glands，including stomach and digestive diverticula，which are good candidate sites for detection of pathogens．

Abstract:Abstract: ［Objective］To exploit resources of purple sulfur bacteria in China and further investigate its response mechanism to ecological environment of mangrove． ［Methods］ Repeated agar shake dilution method，microscope techniques，UV-Vis absorption spectra，thin layer chromatography，HPLC and MS were used． ［Results］We isolated a purple sulfur bacterium，designated as strain YL28，from a intertidal sediment sample collected from inshore mangrove near Luoyang Bridge of Quanzhou city，Fujian Province of China． Cells were ovoid to rod shaped，0.5 μm -1 μm×2 μm-3 μm． Color of cell suspensions was reddish-brown． It possessed vesicular intracytoplasmic membrane structures，contained rhodopin and phytylated bacteriochlorophyll a as well as the other two novel bacteriochlorophyll a intermediates．The optimum growth was at 2%－3.5% NaCl，pH 5.7－6.7 and 20℃－35℃. Photoautotrophically growth anaerobically in the light with sulphide，sulphur，thiosulfate，sulfite as electron donor．Globules of S0 distributed inside the cells．Photoheterotrophic growth with various organic substrates，especially citrate，glucose，sucrose，fructose and propanol in the presence of sulfide． Nitrogen sources: ammonium salts，N2，urea，glutamate，nitrate and nitrite． Vitamins were not required． Qualitative assessment of IC50 values of chloromycetin，cefazolin，benzene，hydroxy biphenyl，enrofloxacin，acetamiprid，mercuric chloride and cadmium chloride were 70，100，20，20，3，170，5 mg /L and 25 mg /L，respectively． ［Conclusion］Based on phenotype characteristics and 16S rRNA gene sequence similarity of 99% to M．gracile，strain YL28 was identified as novel isolate of M． gracile despite its different physiological characteristics with respect to the species of M． gracile． The organism is possessed of slightly acid tolerance，higher amount of carotenoid of rhodopin and tolerance towards certain antibiotics，pesticide as well as heavy metals．

Abstract:Abstract:［Objective］Genetic diversity and phylogeny of bradyrhizobial strains associated with Desmodium spp． in subtropic and temperate regions of China were analyzed．［Methods］ We studied 29 desmodia isolates from different regions with BOX-PCR fingerprinting and multilocus sequence analysis ( nifH，nodC and recA gene) to describe the genotypic characteristics and phylogenetic relationships．［Results］ We achieved 25 genotypes with BOX-PCR genomic fingerprinting analysis，indicating that the tested strains had a great diversity at genomic level． The representative bradyrhizobial strains were located in three phylogenic branches with multilocus sequence analysis (nifH，nodC and recA gene)，that was closely related to Bradyrhizobium elkanii，Bradyrhizobium japonicum and Bradyrhizobium yuanmingense，respectively．［Conclusion］The desmodia bradyrhizobia had abundantly diversity． Diverse symbiotic genes including nifH and nodC genes were also found in these strains that indicated that the symbiotic genes were mainly maintained by vertical transfer in these bradyrhizobial populations and coevolved with housekeeping genes．

Abstract:Abstract:［Objective］ The purpose of this work was to screen strains having tobacco-specific nitrosamines (TSNA) deteriorating activity，isolated from the inner and superficial of tobacco plants． Then strain AS97 was isolated and identified for further application.[Methods] Strain AS97，with the highest conversion ability against both nitrate and nitrite，was screened by enrichment and selective medium． The strain was identified by rphological，physio-biochemical characteristics and 16S rRNA gene sequence analysis．The concentration of 4-(methylnitrosamino)-1-(3-pyridy)-1-butanone (NNK)，N-nitrosonicotine (NNN)，N-nitrosoanatabine (NAT) and N-nitrosoanabasine (NAB) were determined by LC-MS/MS．The fermentation broth of strain AS97 was spraied on the leaves of tobacco to define inoculum concentration and fermentation condition. [Results] AS97 was identified as Pseudomonas fluorescens (Genbank accessionnumber:JF 449445)．Under the optimal growth conditions with inoculum concentration of 5%，at 30℃ for 10 d，AS97 had high biological activity against NNK and NNN with a degradation rate of 59. 08% and 38.79%，respectively．The correlation analysis displayed a pronounced correlation(p ＞0.01) among the concentration of nitrate，nitrite and TSNA．Furthermore，the results also exhibited that nitrate and nitrite were antecedent substance of TSNA. [Conclusion] These results indicated that Pseudomonas fluorescens AS97 could be a promising microorganism in the practice of non-harmful cigarette production．

Abstract:Abstract:［Objective］ Previously，seventeen extracellular polysaccharide-associated mutants of Xanthomonas oryzae pv．oryzicola (Xoc) were acquired from our randomly Tn5-inserted mutant library．To know the Tn5-inserted genes of these mutants and their contribution to EPS production and virulence in rice，［Methods］ in this study，we first identified and characterized the Tn5-targeted genes in these mutants and then inoculated them in susceptible rice for virulence assessment．［Results］ Tn5 transposon was inserted in genes of the gum，xan and wxoc clusters in the majority of EPSreduced mutants． Of the EPS-reduced mutants，three were due to the Tn5 insertion in Xoryp _4217，Xoryp _2488 and Xoryp_0918 genes，respectively． In six EPS-increased mutants，three were in mutagenesis in fimO，pilY and xopQ genes，respectively，resulting in higher EPS production than the wild-type strain RS105． Other three were because of the mutation in Xoryp2392，Xoryp_4221 and Xoryp_3511 genes． Interestingly，XocORF-3511 only exists in X． oryzae but not in other Xanthomomas species． Virulence assays in rice showed that the less EPS production by the mutant，the weaker the virulence in rice． However，those mutants in higher EPS production did not increase virulence significantly in rice compared to that by the wild-type strain． ［Conclusion］Our findings will help further understand the metabolic pathways for EPS synthesis in Xoc and the specific roles of EPS-associated genes in Xoc-rice interactions．

Abstract:Abstract:［Objective］ To analyze the difference of specificity of four primers for betaproteobacterial ammonia-oxidizing bacteria (β-AOB) 16S rDNA gene from the biofilm of closed recirculation aquaculture systems．［Methods］We used 16S rDNA clone libraries to describe the β-AOB diversity． ［Results］ CTO189f /CTO654r produced the highest frequency of β-AOB-like sequences (67.3%)．The amplification performance of primer was noticeably influenced by the biofilm samples． Hereinto，the biofilm of closed recirculation aquaculture systems of Tilapia nilotica resulted in the higher amplification performance of primers．［Conclusion］ CTO189f /CTO654r exhibited the highest specific for β-AOB 16S rDNA gene from the biofilm of closed recirculation aquaculture systems．

Abstract:Abstract:［Objective］ In order to better understand the diversity of cultivable bacteria during the brewing process of the Luzhou-flavor liquor in Yibin，and to collect potential microbial resources． ［Method］ The cultivable bacteria were isolated by using modified nutrient agar medium and Gogan-I medium，and then analyzed the 16S rRNA gene sequences of the 603 non-redundant isolates separated from the air of fermentation workshop，Pit mud，Zaopei，Chinese Qu and air of Qu workshop sampled from 6 luzhou-flavor liquor production enterprise in Yibin． ［Results］ Phylogenetic analysis based on 16S rRNA gene sequences showed that 599 of them belonged to 101 species of 34 genera，and 4 isolates with ＜ 97%sequence similarities to their closely related members were presumed to be potential novel species． Bacillus is the most dominant genus with 315 strains; Streptomyces，Staphylococcus and Lysinibacillus were dominant genera，with 121，45 and 35 strains，respectively． The number of isolates belong to the other 31 genera were less than 10 strains，furthermore，only one strain was detected in 16 genera． ［Conclusion］ Bacteria during the brewing process of the Luzhou-flavor liquor in Yibin present plentiful diversity and relative stability．

Abstract:Abstract:［Objective］ In order to further understand the difference in metabolic regulation between Escherichia coli DH5α and its acetate-tolerant mutant DA19，we analyzed the effect of supplementing adenine in defined media on metabolic fluxes in the two strains． ［Methods］ E． coli DH5α and DA19 were continuously cultured in nitrogen-limited defined media without or with supplemented adenine． Based on mass balance and metabolic reaction stoichiometry，the metabolic fluxes in DH5α and DA19 at different culture condition were calculated，and the results were compared with the activities of key enzymes． ［Results］ The supplementation of adenine decreased specific glucose consumption rate and specific acetate production rate，and improved growth yield coefficient on glucose of DH5α． Nevertheless，specific pyruvate production rate did not significantly change． Furthermore acetate split ratio decreased whereas pyruvate and TCA split ratios increased． Obvious changes were observed in the activities of phosphofructokinase， 6-phosphoglucose dehydrogenase and acetokinase． Compared with DH5α，the supplementation of adenine increased rate specific pyruvate production rate of DA19 nearly 57% ，and other parameters did not change． In addition，it showed decreased TCA split ratio and greatly increased pyruvate split ratio，whereas no changes in the key enzyme activities were observed．The differences of enzyme activities in the two strains were reasonably consistent with those in metabolic fluxes． ［Conclusion］Because there were differences in the de novo biosynthesis capacity of purine nucleotides between DH5α and DA19，supplementation of adenine had completely different effect on metabolic fluxes in two strains．

Abstract:Abstract:［Objective］ The diversity of rumen microbial xylanases and their degradation characteristics were studied and the resources of new xylanases genes and enzymes were provided．［Methods］According to the result of the highthroughput sequencing of the rumen microbial metagenome bacterial artificial chromosome (BAC) clones library，the diversity of xylanase genes was analyzed and screened． Then one xylanase and its downstream xylosidase gene screened was cloned and expressed in Escherichia coli． The enzyme characterization of the recombinant xylanase and xylosidase and their synergistic effect were studied．［Results］All 14 xylanases screened from the library belong to GH10 family proteins．These xylanases shared the amino acid sequence similarity between 20. 5% and 91.3%．Intriguingly，7 xylanase genes in different contigs were found to be followed by xylosidase gene． The specific enzyme activity of the xylanase (Xyn32) was 1.98 U /mg and no ferulic acid esterase activity was detected．The specific enzyme activity of the coupled xylosidase (Xyl33) was 0.07 IU /mg，and xylosidase (Xyl33) also displayed the activity of arabinofuranosidase．In addition，the in vitro experiment confirmed the synergistic effect between the coupled xylanase and xylosidase．

Abstract:Abstract:［Objective］To clone cDNA sequences of lipase 4 (LIP4) and lipase 5 (LIP5)，analyze gene structures and express them in Pichia pastoris so as to investigate their enzymatic characteristics．［Methods］ We first cloned cDNA sequences of LIP4 and LIP5 by reverse transcription PCR and analyzed their gene structures by SignalP 3.0．Then，intracellular expression vectors pPIC3. 5K-Lip4，pPIC3. 5K-Lip5 and inducible secretion vectors pPIC9K-Lip4，pPIC9KLip5 were constructed． All vectors were transformed into Pichia pastoris GS115 by electroporation，resulting in a series of engineered strains． After fermentation and NTA-Ni resin purification，the enzymatic properties of LIP4 and LIP5 were examined．［Results］ The cloned cDNA sequences revealed that there was no intron in both of Lip4 and Lip5．The two lipases both contained catalytic triads and conserved GHSLG motifs． Their optimal substrate，pH，temperature were respectively pNP-caprylate (C8)，7.0 and 40°C．The activities of LIP4 and LIP5 were 10.16 U/mg and 5.1 U/mg，respectively． It was found that LIP4 was more sensitive to the variations of pH and temperature than LIP5． LIP4 and LIP5 could both be stimulated by Ca2 + ，besides LIP5 could also be activated by Mg2 + ． They were both strongly inhibited by Hg2 + ，Phenylmethanesulfonyl fluoride ( PMSF) and Dithiothreitol (DTT) ． ［Conclusion］The cloning of Lip4 and Lip5，expression in P． pastoris and characterization of their properties would offer a solid basis for their large-scale production and future application． In addition，the results also enriched the data for a systematic research on the lipase gene family of Y．lipolytica．

Abstract:Abstract:［Objective］ Two heterotrophic nitrifying bacteria，P2 and P9 isolated from piggery wastewater，were studied for their capacity of nitrification and nitrogen removal． ［Methods］ Physiological characteristics and phylogenetic analysis based on 16S rDNA sequences of strains P2 and P9 were analyzed． The ammonia removal characteristics of strains P2 and P9 were investigated． Furthermore，nitrogen removal ability of strains P2 and P9 individually or mixed were evaluated in the treatment of actual piggery wastewater． ［Results］ Strains P2 and P9 were identified as Paracoccus sp． and Shinella sp.,respectively． Heterotrophic nitrification could occur by the strains when they utilized organics． After cultivation of 24 h，the ammonia removal rates by the strains were up to 80% approximately; meanwhile，there was almost no nitrite and nitrate accumulation． However，aerobic denitrification could not occur by the strains when NO－3 or NO－2 was provided as the sole nitrogen source，respectively．For heterotrophic nitrification，with strains P2 and P9，the optimal carbon source was sodium succinate，and the optimal C /N ratio was 9． Besides，the pH values rose from 6.8 to 8.9 in the whole ammonia removal process． The growth and nitrogen removal ability of the two strains depended much on the quantity of small molecule carbon source，and the nitrogen removal capability of strains P2 or P9 in wastewater with small molecule carbon source was improved evidently． The effect was strengthened especially when the two strains were mixed together．［Conclusion］ Nitrogen removal ability of strains P2 and P9 was relatively strong，and they may exhibit broad application prospects in wastewater treatment．

Abstract:Abstract:［objective］ We investigated the correlation between the methanogen diversity in the piglet colon and the environmental factor (weaning stress，diet type and age) ． ［Methods］ The colonic contents of piglets at 7，14，21，28 and 35 days old were collected for the determination of volatile fatty acids and total DNA extraction． DNA was subject to PCR-DGGE ( Denaturing gradient gel electrophoresis ) analysis and interesting bands were excised and sequenced．Redundancy analysis (RDA) was performed for the correlation between methanogen diversity and environmental factors． ［Results］ As the piglets grew，acetate，propionate and the total volatile fatty acid production increased significantly (P＜0.05)，but butyrate concentration remained stable (P＞0.05)．The similarity indices of DGGE profiles was higher during the period of the 7 day to 24 day after birth，with grouped in one cluster，and the samples from the 35 days were dropped into another cluster． DGGE analysis showed three dominant bands appeared in samples of 35 d old，with their 16S rRNA gene sequences closely related to Methanobacteria and a novel group of uncultivated Achaean． Redundancy analysis (RDA) showed that age has the largest relevance to the community structure of bacteria in colonic samples，followed by the diet type． ［Conclusion］The results indicated that the methanogen community in the piglet colon was stable during the first 24 days after birth，and became more diverse at 35 days of age． The methanogens community was mainly affected by age and the diet type．

Abstract:Abstract:［Objective］ Feather follicle epithelium (FFE) and feather of chicken are sites that produce and release enveloped infectious Marek's disease virus (MDV) ． In order to investigate host responses，the feather pulp from chickens infected with MDV was analyzed by proteomics．［Methods］ Forty-eight one-day old specific pathogen free (SPF)chickens were randomly divided into two groups． One group of birds (n=24) were inoculated intraperitoneally with 1000 plaque-forming unit (PFU) of the RB1B strain of MDV，the rest (n = 24) kept as uninfected control． Feather pulp were extracted from feather tips collected from chickens of infected and control group at 21 days post infected (dpi)，and dissolved in two dimensional electrophoresis (2-DE) sample buffer． The soluble proteins were separated by 2-DE，6 images (2 groups×3 images) of 2-DE were used to analyze the differentially expressed proteins with PDQuest 8.0.1．Some of spots changed significantly were further analyzed by mass spectrometry．［Results］ 41 spots，which expression level changed above two fold，were detected． Among of them，25 of these spots were up-regulated，7 spots downregulated， 9 spots newly induced expression in group infected with MDV． 21 spots，corresponding to 20 proteins，were successfully identified by mass spectrometry． These differential expressed proteins are apolipoprotein A I，14-3-3 sigma (two spots are the same protein)，stathmin，and so on．［Conclusion］Bioinformatics analysis indicates these differential proteins are mainly associated with host response，metabolism，cytoskeleton，and cell proliferation．

Abstract:Abstract:［Objective］ To study the immunosuppression effect on the thymus of muscovy ducks after infected with muscovy duck reovirus (MDRV) and H9 influenza virus (AIV)．［Methods］ After 8-day-old birds were infected with MDRV or H9 AIV，or both，the morbidity and mortality were totaled，the morphology and ultra-structure of the thymus were observed，proliferation ability of thymus cell were detected and the virus distrubition were detected by RT-PCR．［Results］After H9 AIV infection，The morbidity was low (10%) and without death． No obvious pathological change was observed on the thymus，whereas the proliferation ability of thymus cell was obviously suppressed． After MDRV infection，The birds grew slow，the morbidity was 80% and mortality was 50% ． Thymus was atrophy appearing local necrosis and proliferation ability of thymus cell was obviously suppressed． After co-infection with MDRV and H9 AIV，the birds grew even slower growth． The morbidity was 90% and mortality was 70% ． The thymus was atrophy appearing the lymphopenia and local necrosis and proliferation ability of thymus cell was also more obviously suppressed than MDRV infection． Virus duration time and detection ratio in co-infection group were more than in AIV and MDRV group． ［Conclusion］H9 AIV could lead to minor immunosuppression and MDRV could cause serious immuno-suppression． H9 AIV could aggravate the immunosuppression of thymus after co-infected with MDRV，so MDRV and H9 AIV infection had synergic effect on immunosuppression of the thymus．

Abstract:Abstract: ［Objective］ Antimicrobial susceptibility to quinolone and fluoroquinolones and the related genes of chickenborne Salmonella in Shaanxi，Henan， Sichuan and Beijing provinces were studied to better understand the development of antimicrobial resistance and routes of transmission to ensure food safety． ［Methods］ Antimicrobial susceptibility was tested according to agar dilution method． GyrA and parC gene mutations of quinolone resistance determination region (QRDR) of fluoroquinolone resistant Samonella and the resistant genes of qnrA，qnrB，qnrS and aac (6’) -Ib-cr were determined using PCR and DNA sequencing analysis． ［Result］ Among the 390 Salmonellae isolates，63. 59% were resistant to nalidixic acid，followed by ciprofloxacin (21. 28% ) ，levofloxacin (16. 67% ) ，and gatifloxacin(14. 62% ) ． Among 248 nalidixic acid resistant Salmonella， antimicrobial resistant genes carried by plasmid weredetected as aac(6’) -Ib-cr (20. 16% ) ，qnrA (10. 89% ) ，qnrB (10. 08% ) and qnrS (1. 61% ) ，respectively． In total 199 point mutations were detected in gyrA and parC of 83 fluoroquinolone-resistant Salmonella isolates． The most common mutations in gyrA gene was Ser83Phe and Asp87Gly double mutation，followed by Ser83Phe and Asp87Asn double mutation，Ser83Tyr，Ser83Phe，Asp87Gly． Sixty-five point mutations detected in parC was Ser80Arg ． ［Conclusion］Antimicrobial resistance of Salmonella recovered from chicken in the four provinces was common． Genetic elements including mutations of unwindase， topoisomerase， and plasmid with antimicrobial， played important roles in the antimicrobial resistance of Salmonella．

Abstract:Abstract:［Objective］ To study the heterogeneity and immunogenic variability among Mycoplasma ovipneumoniae (M.ovipneumoniae) isolates from differnt regions of China．［Methods］The heterogeneity of 17 strains of M. ovipneumoniae isolated from 8 regions of China was studied by the amplified fragment length polymorphism (AFLP) and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE)．The software NTsys-2. 10e was used to analyze the profiles obtained from the AFLP and SDS-PAGE．The proteins reacted with the antiserum against M．ovipneumoniae type strain Y98 were then detected by Western-blot．［Results］ Seventeen strains of M． ovipneumoniae were divided into 8 AFLP groups based on the source regions when the coefficient was 0. 78． They were also divided into 8 SDS-PAGE groups based on the source regions when the coefficient was 0. 85． A total of 6 immunogenic proteins were detected within 8 strains of M．ovipneumoniae， and their molecular weights were 105 kDa，83 kDa，65 kDa，42 kDa，40 kDa or 26 kDa，respectively． Interestingly，the 83 kDa and 40 kDa proteins were conserved in all the 8 isolates． ［Conclusion］ M．ovipneumoniae isolates from some regions of China were genetically different，but the 83 kDa and 40 kDa antigenicproteins were conserved among the tested isolates． This study can provide some insights for the diagnosis and vaccine development of the disease caused by M．ovipneumoniae．