Abstract:Abstract:The regulatory mechanism of bacterial cell division has long been a research focus．Forming a septum at the middle of the cell，the seemingly simple process is involved by multiple regulation factors． Zring (FtsZ ring) is the skeleton of the splitting complex．The locus where Z ring is formed is not only the position the septum formed but also determines the cell division site． Formation ofZring in the incorrect location results in inequality cell division． Several cell division regulation systems have been identified，including the Min system，nucleoid occlusion and the MipZ protein which effectively prevent Zring assembly by different mechanisms，ensuring formation of the fission complex at the correct position． Recent progresses about the formation process of Zring and regulation mechanism affecting the Z-ring positioning are summarized．

Abstract:Abstract:［Objective］In this study，we constructed a recombinant Escherichia coli strain for the production of high-purity L-lactic acid，using a homoethanol fermenting mutant E．coli SZ470 (ΔfrdBC ΔldhA ΔackA ΔfocA-pB ΔpdhR::pBp6-pBrbs-aceEF-lpd) as the starting strain． ［Methods］By using homologous recombination，we deleted the adhE gene from SZ470 to obtain a mutant Escherichia coli JH01，which could not grow under anaerobic conditions． Then we cloned the Llactate dehydrogenase gene (ldhL) of Pediococcus acidilactici and inserted it into the chromosome of JH01 via electroporation to obtain a recombinant strain Escherichia coli JH12． We evaluated the L-lactic acid production of the recombinant strain in a 15 L fermenter．［Results］In 10 L LB medium supplemented with 6% glucose，JH12 maintained maximal cell growth and an efficient L-lactic acid production rate for 36 h． Glucose consumption rate achieved was 1.46 g/(L·h) and L-lactic acid production rate was 1. 14 g/(L·h)．The results also show that 41.13 g/L lactic acid was produced，achieving a purity of 95.69% (based on total fermentation products) ．Xylose consumption rate was 0.88 g/(L·h) and L-lactic acid production rate was 0.60 g/(L·h)．The production of lactic acid was 34.73 g/L， achieving a purity of 98%．There were no succinic acid and formic acid detected and only little amount of acetic acid generated during the fermentation．［Conclusion］ We constructed a homolactic acid fermentation strain E． coli JH12，which could efficiently convert glucose and xylose into high-purity L-lactic acid． JH12 could have great potential in industrial fermentation for L-lactic acid production．

Abstract:Abstract:［Objective］We detected and analyzed transcript profile differences between hexose and pentose fermentation by Candida shehatae，a typical xylose fermenting yeast strain． On this basis，the encoding genes of key enzymes and functional protein were screened for discovering candidates of metabolism and regulation．［Methods］To discover the key genes of xylose metabolism and ethanol fermentation in Candida shehatae，we performed a new high throughout de novo transcriptome sequencing technology on Roche 454 GS FLX Titanium platform． Two cDNA libraries were constructed and sequenced for xylose and glucose fermentation for comparison of its expressed sequence tags differences． ［Results］Second sequencing run resulted in 600000 reads with the average length of 400bp for each cDNA library．We got 7250 and 7168 contigs by assembly，and annotated 2412 and 2456 unique genes by BLAST and Gene Ontology analysis for xylose and glucose respectively． By comparison，we identified 158 genes as different expression genes candidates at p＜0.05 for xylose metabolism and ethanol fermentation in Candida shehatae．［Conclusions］The group genes for xylose metabolism and ethanol fermentation in Candida shehatae was discovered by using transcript profile sequencing and comparison．It will provide fundamental data for the relative research on molecular biology and metabolic regulation．

Abstract:Abstract:［Objective］ To reveal the correlation between thermostability of xylanase EvXyn11TS and its N-terminal disulfide bridge，an EvXyn11TS-encoding gene (Syxyn11) was synthesized and subjected to site-directed mutagenesis．［Methods］Multiple homology alignment of protein primary structures between the EvXyn11TS and several GH family 11 xylanases displayed that，in their N-termini，only EvXyn11TS contained a disulfide bridge (Cys5 -Cys32)，whose effect on the xylanase thermostability was predicted by molecular dynamics simulation．We constructed a gene Syxyn11M，encoding the mutated xylanase (EvXyn11M ) without N-terminal disulfide bridge．Then，Syxyn11 and Syxyn11M were expressed in Pichia pastoris GS115，and temperature and pH properties of the expressed enzymes were analyzed．［Results］The analytical results displayed that the temperature optimum of EvXyn11M was 70℃，which was 15℃ lower than that of EvXyn11TS．The half-life (t1/290) of EvXyn11TS at 90℃ was 32 min，while the t1/270 of EvXyn11M at 70℃ was only 8.0 min．［Conclusion］The important role of the N-terminal disulfide bridge on the thermostability of EvXyn11TS was first predicted by molecular dynamics simulation，and confirmed by site-directed mutagenesis． This work provided a novel strategy to improve thermostabilities of the mesophilic family 11 xylanases with high specific activities.

Abstract:Abstract:［Objective］Use of renewable plant biomass is an active area in current biotechnology research． This report explores the cellulose-degradation system and the factors affecting cellulase gene expression in Chaetomium globosum NK102．［Methods］In the sequenced genome，we identified 10 cellulase genes by sequence homology alignment． We used a high-throughput sequencing technology (RNA-Seq) to monitor the differential expression of the genes under different culture conditions．［Results］We observed that cellulase activity increased with time in the fungal cultures．Accordingly，transcription of the genes encoding cellobiohydrolase，cellobiose dehydrogenase and endoglucanase (cbh1， cdh and egl1) was higher than the others． Expression of the transcriptional repressors，ACE I and CreA，decreased with the time，whereas expression of Hap2/3/5 complex was upregulated． In different carbon sources，cellulase activity and their gene transcription were repressed by glucose and were activated by cellobiose． Sorbitol had no significant effect．Interestingly，light affected positively the expression of these cellulase genes． ［Conclusion］ Differential RNA-seq analysis can make preliminary exploration on the expression regulation of cellulase genes． Expression of the genes in C．globosum was determined by different culture conditions． This study has shown a molecular system of cellulose-degradation in C．globosum and provides information for interpretation of carbohydrate metabolism．

Abstract:Abstract:［Objective］ To clone and characterize the alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) from Bacillus pseudofirmus OF4． ［Methods］Genes of adh and aldh were cloned by PCR; expression vectors pET-Ahd and pET-Aldh were constructed and expressed in Escherichia coli BL21 (DE3)．After Ni-NTA column chromatography purification，the protein was characterized．［Results］The optimal temperature and pH of ALDH was 35℃ and 8. 0，the specific activities of ALDH was 979.6 U/mg protein，the thermostability at 25℃ and 35℃ was better than at 45℃ ． Although the expression level of ADH was too low to purify，but it was found that ADH had high catalytic activities by experiments of co-expression and ethanol tolerance．［Conclusion］Adh and aldh from B． pseudofirmus OF4 were cloned successfully． Co-expression of double genes could greatly increase the host strain on ethanol tolerance.

Abstract:Abstract:［Objective］We obtained an alkali-tolerant denitrifying bacterium，and determined its denitrifying activity and alkali-tolerance． ［Methods］An alkali-tolerant denitrifying bacterial strain was obtained by isolation and purification．We identified the bacterial strain by morphological observation，physiological test and 16S rRNA analysis． We determined the denitrifying activity and alkali-tolerance by effects of initial nitrate concentration and initial pH on denitrification．［Results］An alkali-tolerant denitrifier strain R9 was isolated from the lab-scale high-rate denitrifying reactor，and it was identified as Diaphorobater nitroreducens． The strain R9 grew heterotrophically with methanol as the electron donor and nitrate as the electron acceptor．The nitrate conversion was 93. 25% when strain R9 was cultivated for 288 h with initial nitrate concentration 50 mg/L and initial pH 9.0．The denitrification activity could be inhibited at high nitrate concentration with a half inhibition constant of 202.73 mg N/L．Strain R9 showed a good alkali tolerance with the nitrate removal rate at pH 11.0 remained 86% of that at pH 9.0．［Conclusion］ Strain R9 was identified as Diaphorobater nitroreducens，and it was an alkali-tolerant denitrifying bacterium with optimum pH value of 9.0.

Abstract:Abstract:［Objective］We isolated myxobacteria in saline-alkaline soils of Xinjiang using a prey-predator strategy where the prey bacteria can induce the predator myxobacteria to form visible fruiting body，and evaluated intrinsic relationships between prey and predator myxobacteria． ［Methods］ Sixteen bacteria with inductive effects of fruiting body formation were obtained，and then used as preys to isolate the myxobacteria． ［Results］ A total of 55 myxobacteria strains were isolated from 25 soil samples，which were identified to the genera of Myxococcus，Corallococcus，Pyxidicoccus，Cystobacter，and Nannocystis． Besides，6 unpurified isolates were believed to be myxobacteria． All the 16 prey bacteria had preferable inductive effects on Myxococcus spp． ，whereas Pyxidicoccus spp． and Cystobacter spp． were only induced by Gram-positive strains． ［Conclusion］ The prey-predator strategy provided a new and more effective way to isolate myxobacteria．

Abstract:Abstract:［Objective］ Positive regulatory factor A (PrfA) protein plays a key role in the pathogenicity of Listeria monocytogenes by regulating the expression of virulence genes．We studied the regulation functions of PrfA and its role in Listeria monocytogenes (Lm) virulence． ［Method］Extracellular proteins were obtained from the supernatants of parental strain LM4 and mutant strain LM4ΔprfA cultured in minimal medium． We used two-dimensional gel electrophoresis and matrix associated laser dissociation/ionization time of flight mass spectrometry (MALDI- TOF-MS) to analyze the differences of secreted proteins between LM4 and LM4ΔprfA．［Results］The electrophoresis results show that 31 different spots，19 spots corresponding 12 proteins were identified by MALDI- TOF-MS． Some virulence related proteins were verified，such as InlC，ActA and LLO． Some new proteins that are regulated by PrfA include D-alanyl-D-alanine carboxypeptidase，dipeptide Glycine and Trytophan (GW) repeat-containing surface protein，transcriptional regulator and some hypothetical proteins with unknown functions． Real-time quantitative PCR was conducted to verify the proteomics results． The mRNA expression level of hly，actA and inlC gene was significantly reduced，and that of D-alanyl-D-alanine carboxypeptidase and GW repeat-containing surface protein's synthesis also had a reduction in LM4ΔprfA strain． ［Conclusion］PrfA plays key roles on the regulation of genes in LIPI- I and LIPI- II．

Abstract:Abstract:［Objective］The gene of ice nucleation protein (INP)，an outer membrane of Pseudomonas syringae was tested to display foreign proteins on the surface of Lactococcus lactis．［Methods］ Plasmids pHZ101 and pHZ102 were constructed using gfp (Green Fluorescence Protein) as the reporter gene and N-terminal and NC-terminal of inp as the anchoring units． Plasmids pHZ101 and pHZ102 were subsequently transformed into Escherichia coli JM109 and Lactococcus lactis MG1363．［Results］ Fluorescence microscope shows that green flrorescence was observed in both recombinant E．coli and L． lactis strains． Western blot indicated that GFP was expressed in both recombinant E.coli and L．lactis strains． INPN-GFP was mostly trapped in cytoplastic fraction while INPNC-GFP was mainly targeted on the cell membrane of L．lactis．［Conclusion］The results suggest a new way to construct cell surface display system of lactic acid bacteria by using ice nucleation protein．

Abstract:Abstract:［Objective］ From oral cavity we isolated and characterized probiotic lactobacilli that could probability be applied to therapy and prevention of oral diseases. ［Methods］Lactobacillus strains were isolated by plating the saliva and dental plaque of healthy donors on selective medium．Then the target strains were tested for inhibiting the growth of a Streptococcus mutans strain belonging to cariogenic pathogen species．Other properties such as production of extracellular polysaccharide and resistance to the antibacterial substances were also investigated．［Results］ Lactobacillus fermentum Y29，a strain with antimicrobial activity against Streptococcus mutans，was obtained from dental plaque．This strain was an extracellular polysaccharide producer，which corresponds to its aggregation ability． Moreover，L． fermentum Y29 showed resistance to 1.0 mg/mL lysozyme and 140 μg/g hydrogen peroxide that may guarantee its persistence in the complex oral niche． ［Conclusion］ Probiotic properties were characterized of an oral isolate L．fermentum Y29，which provided a possibility for its application in prevention and treatment of oral diseases．

Abstract:Abstract:［Objective］To sequence the complete genome of CVS-11 strain and establish a reverse genetic system of CVS-11 to further study its pathogenic mechanism，virulence genes and antigenic sites．［Methods］We amplified12 fragments covering the complete genome of the CVS-11 strain by RT-PCR，and then cloned to pEASY-Blunt vector for sequencing the complete genome of CVS-11．We analyzed single restriction enzyme sites of the full length cDNA of the CVS-11 strain by DNAMAN and designed 4 pairs of specific primers．We amplified the full-length cDNA of CVS-11 by RT-PCR．We obtained four fragments and cloned into pcDNA3.1．We named the full-length cDNA plasmid pcDNA3. 1-CVS-11．We also cloned helper plasmids pcDNA3. 1-N，P，L and G expressing N，P，L and G protein of CVS-11 strain，respectively．We co-transfected NA cells with the full-length plasmid and four helper plasmids．We identified the supernatant of the transfected and then passaged NA cells by immunofluorescence staining and RT-PCR and found the recombinant virus rCVS-11 rescued successfully．［Results］Sequencing results showed that the complete genome of CVS-11 was composed of 11 927 nucleotides． The complete genome of CVS-11 encoded 5 structure proteins and gene array was the same as other reported rabies viruses． We successfully constructed a reverse genetic system of CVS-11，namely the full length plasmid pcDNA3. 1-CVS-11 and 4 help plasmids pcDNA3. 1-N，P，L，G and rescued the rCVS-11 from a full-length infectious cDNA clone．［Conclusion］ The reverse genetic system of the CVS-11 strain laid the foundation for future studies on rabies virus．