Abstract:

Abstract:[Objective] To study the effect of K release and weathering of K-bearing minerals by Penicillium oxalicum. [Methods] The element compositions in the liquid phase and on the mineral surface were determined by Inductively Coupled Plasma, X-ray Energy Dispersive Spectrometer and X-ray Photoelectron Spectroscopy. The crystal structure was analyzed by X-ray diffraction after the mineral was incubated with P. oxalicum. The biofilm formed onto K-bearing minerals was determined by Confocal Laser Scanning Microscope. The effect of carbon source and nitrogen source on K mobilization by P. oxalicum was also studied. [Results] Biotite showed less resistance to fungal bioweathering, compared with K-feldspar and muscovite, and P. oxalicum formed network structure biofilm where probably the organic acid was concentrated. Different carbon and nitrogen source could be used by P. oxalicum. [Conclusion] P. oxalicum can accelerate the bioweathering and K release of different K-bearing minerals and has application potential in compost and biofertilizer.

Abstract:

Abstract:[Objective] To investigate the structure and function of PHB synthesis family protein, we cloned the phaB and phaE of Synechocystis sp. PCC 6803 and constructed prokaryotic expression vectors. The conditions of cell culture were optimized for improving the expression level of soluble protein and then the crystallization condition of SpPhaB was screened. [Methods] The phaB and phaE were cloned from Synechocystis sp. PCC 6803 by PCR and ligated to pET28a expression vector. To improve the expression of SpPhaB and SpPhaE, the culture conditions including IPTG concentration, temperature and induction time were studied. Ni-NTA resin was used to purify His-SpPhaB and His-SpPhaE protein, and initial crystal culture condition of SpPhaB was screened. [Results] The sequencing results showed that pET28a-SpPhaB and pET28a-SpPhaE expression vectors were constructed successfully. The optimized condition for SpPhaB expression was determined to be: induction at 37 °C using IPTG concentration of 0.1 mmol/L, the induction time was 7 h and the rotation speed was 220 r/min. The optimized condition for SpPhaE expression was determined to be: induction at 25 °C using IPTG concentration of 0.5 mmol/L, the induction time was 7 h and the rotation speed was 220 r/min. [Conclusion] The pET28a-SpPhaB and pET28a-SpPhaE were constructed successfully and the crystallization conditions of SpPhaB have been optimized. It provided the foundation for investigating the structure and function of SpPhaB.

Abstract:[Objective] Phenylalanine ammonia lyase from Anabaena variabilis (AvPAL) was expressed and molecular modified to decrease its optimum reaction pH. [Methods] The full length AvPAL gene was cloned and expressed in E. coli BL21(DE3). The recombinant protein was purified through Ni2+ affinity chromatography and gel filtration chromatography. The mutation sites were decided by GETAREA software to choose the amino acid sites both closed to the catalytic group and exposed to the surface of the enzyme. After changing the electric properties of the target amino acid residues, enzymatic properties of the mutants were studied. [Results] The recombinant AvPAL was successfully expressed in E. coli BL21(DE3). SDS-PAGE analysis showed that the recombinant enzyme of electrophoresis pure was obtained. The optimal reaction pH of E75Q and E75R mutants were shifted to 7.5 and 7.0, respectively, in contrast to pH 8.5 of the wild type (WT). The E75Q had a 25% higher specific activity than AvPAL WT at pH 7.5, and there was a good stability between pH 6.5 and pH 9.5. The optimal reaction temperature of E75Q was 50 °C. At the same time, the E75Q had a good stability under 50 °C with no obvious reduction in enzymatic activity after incubation of 1 h. Under the optimal reaction conditions, the kcat/Km was increased by 26.6% compared to the AvPAL WT. [Conclusion] The optimal reaction pH of AvPAL was decreased by altering the charge of amino acid residues which were in a hypothetical position to interact with the general base catalyst. The resulting mutant would improve the application prospect of AvPAL in therapeutic.

Abstract:[Objective] To understand the adaptability of Marichromatium gracile YL28 to nitrite environment. [Methods] When YL28 was grown with nitrite as the sole nitrogen source or with nitrite-ammonium as coexisting nitrogen sources, the removal efficiency of ammonium-nitrogen and nitrite-nitrogen, the effect of nitrite on bacterial growth and total amounts of photopigments including carotenoids and bacterio chlorophylls were studied by spectrophotometry. The effect of nitrite on compositions of carotenoid and bacteriochlorophyll was investigated by thin layer chromatography. [Results] Strain YL28 was capable of growing with nitrite as the sole nitrogen sources; mainly accumulated two BChl a intermediates (BChl aTHGG and BChl ap), bacterio pheophytin (BPhe) and four carotenoids (rhodopin, spirilloxanthin, anhydro rhodovibrin and lycopene). Bacterial growth and nitrite removal efficiency were decreased with increasing nitrite concentration, more than 200 mg/L of nitrite could be completely removed by strain YL28. When nitrite concentration reached to 25 mg/L, the total amounts of carotenoid and bacteriochlorophyll were decreased dramatically, whereas the relative contents of BChl ap (end product of BChl a biosynthesis), spirilloxanthin (end product of carotenoids biosynthesis) and Bphe increased. When YL28 was grown with nitrite-ammonium as coexisting nitrogen source, the tolerance of YL28 to nitrite and removal efficiency of nitrite by YL28 were significantly enhanced compared with nitrite as the sole nitrogen source, more than 300 mg/L of nitrite was completely eliminated by strain YL28. The inhibitory of nitrite on photopigment biosynthesis was alleviated, the total amounts of carotenoid and bacteriochlorophyll were enhanced, the changes in photopigment compositions were similar to those with nitrate as the sole nitrogen sources. [Conclusion] YL28 could remove nitrite. High concentration nitrite inhibited bacterial growth and photopigment biosynthesis, but the presence of ammonium together with nitrite could promote the tolerance of strain YL28 to nitrite. This work should be helpful to develop novel marine water cleaner for high efficient removal of nitrite.

Abstract:[Objective] The aim of this study is to screen lead-zinc tolerant fungus for the bioremediation of heavy metal pollution in Zixing, Hunan. [Methods] The fungus J3 which was isolated from the local tailing of lead-zinc deposit was used. Orthogonal test was carried out for studying adsorption conditions optimization and biosorption mechanism was discussed by kinetics simulation. And morphological characteristics and 18S rRNA gene sequence analysis were used for identification. [Results] Under the optimal conditions, the results showed that the removal rate of Pb2+ and Zn2+ by growing strains reached 92.2% and 87.7%, while the removal rate of Pb2+ and Zn2+ by dry biomass was 72.6% and 23.8%. The results of kinetics study indicated that the absorption by growing strain was affected by the concentration of Pb2+ and Zn2+. The intra-particle diffusion was the main rate-controlling step for the adsorption of Zn2+. The adsorption of Pb2+ by dry biomass may be affected with membrane diffusion and intra-particle diffusion at the same time. And the adsorption process of Zn2+ was controlled by membrane diffusion. According to the morphological characterization and phylogenetic tree, J3 was preliminarily identified as Verticillium insectorum. [Conclusion] The growing strain had better adsorption effect than the dry. The result which fitted to the second-order equation can provide the basis and guidance for bioreactor settings.

Abstract:[Objective] to get a deodorizing bacillus of high efficient ammonia degradation, and to investigate the process of the nitrogen migration of the strain. [Methods] An ammonia-oxidizing strain was screened in a self-designed screening platform. Colonial morphology, physio-biochemical tests and 16S rRNA gene sequence analysis were adopted to determine the phylogenetic position of the isolated strain. The nitrogen migration characteristics and process of the strain that cultured by NH4Cl as the sole nitrogen source were investigated by using the chemical detection of NH4+-N, NO2?-N, NO3?-N and gases under aerobic and anaerobic conditions. [Results] A high efficient ammonia-oxidizing and deodorizing strain that has the characteristics of heterotrophic nitrification and aerobic denitrification was screened and identified as Bacillus coagulans. Under aerobic and anaerobic conditions, the NH4+-N oxidizing rate of the strain RJCC-03 could reach 98% and 23.7%, respectively. A small amount of N2, not nitrogen oxides gases, was generated during the experiment process, under aerobic conditions. [Conclusion] These results proved Bacillus coagulans had great potential application in the agricultural and environmental protection.

Abstract:[Objective] Biolog-FF system with 95 kinds of carbon source was used to exploit the metabolism feature of four fungi in chlortetracycline degradation. [Methods] The changes of absorbance values of the four strains in 95 kinds of carbon sources were determined in different time. The total organic carbon (TOC) contents were measured after the four strains were inoculated into the chlortetracycline solid waste in different time. [Results] The four strains digested different carbon sources, and the activities of them were quite distinct. 41 kinds, 39 kinds, 15 kinds and 14 kinds of carbon were used by Penicillium citrinum LJ318, Trichoderma harzianum LJ245, Penicillium spinulosum LJ236 and Penicillium oxalicum LJ302, respectively. The average activity digesting carbon of LJ245 and LJ318 were significantly higher than that of the strain LJ236 and LJ302. All the four strains could utilize sugars, amino acids, polymers and so on. [Conclusion] Carbon metabolism of LJ245 and LJ318 in residue were significantly faster than LJ236 and LJ302. This show the same results as what the Biolog system drew out. Biolog technology is an effect method in the study of carbon metabolic characteristics of fungi. This study would build a scientific foundation for investigating the characteristics of fungal carbon metabolism, and for the bio-degradation of chlortetracycline in environment.

Abstract:[Objective] The purpose of this work was to identify the insertion site of mutant Mxac56-20 with reduced extracellular enzyme activities, and to characterize the function of the mutated gene. [Methods] The Tn5 flanking sequence was identified by using plasmid rescue method. After the complementary recombinant was constructed, the restorations of extracellular enzyme and pathogenicity on host plant were tested. [Results] Tn5 transposon was inserted in the general secretion pathway xpsD gene in Xanthomonas citri subsp. citri. The phenotypic alterations were restored when constitutively expressing xpsD gene in mutant Mxac56-20. [Conclusion] The mutagenesis of xpsD gene in X. citri subsp. citri led to the reductions in extracellular enzyme activities and pathogenicity on host plant. These collected data demonstrated that the general secretion pathway is required for full virulence on host plant by X. citri subsp. citri.

Abstract:[Objective] In order to figure out the infection relationship between Rhizoctonia solani AG1 IA and Zoysia japonica, and provide a theoretical basis for further research on pathological infection mechanism, as well as molecular breeding for disease resistance of turfgrass. [Methods] Z. japonica was infected by R. solani AG1 IA through root inoculation, the disease incidence of leaves and plants, disease index were analyzed. Meanwhile, the infection process and methods was studied using histological staining transparent technology and paraffin sections. [Results] The hyphae of R. solani AG1 IA hyphae firstly adsorbed, and then grew directionally along the surface of the tissue, followed by the formation of infection cushion. The hyphae penetrated the tissues through intercellular spaces and invaded the cortical cells, and gradually extended inward the vascular system except xylem vessels. The underground and ground part of Z. japonica showed disparate host response against R. solani AG1 IA. [Conclusion] Infection process of R. solani include adsorption, directional growth, penetration, colonization. The infection of R. solani mainly cause Z. japonica leaves lesions. There are no direct correlation between Z. japonica lesions and infecting hyphae. This might indicate that R. solani has the complex mechanism of pathogenicity.

Abstract:[Objective] This study aimed to character the succession of bacterial community in the litter during the fermentation of duck bio-bed. [Methods] The experiment was conducted in one meat duck bio-bed farm of Jiangsu province. The new litter (D0), used litter from 4th (D4), 8th (D8) meat duck flock and feces from duck at 34 d age were sampled. Denaturing gradient gel electrophoresis (DGGE), 16S rRNA gene sequencing and quantitative real-time PCR were used to monitor the composition changes of microbiota in the bio-bed. [Results] DGGE profiles showed that, the similarity between D4 and D8 was 81.93%, which was significantly higher than the similarity between D4, D8 and D0 (68.81% and 70.82%, respectively) (P<0.05). Bands 6 and 8 (the closest relatives: Leqionella tunisiensis and Pedobacter bauzanensis, respectively) were dominant in all litter samples. Band 10 (the closest relative: Rummeliibacillus suwonesis) was only dominant in used litters. Bands 12 and 13 (the closest relatives: Psychrobacter sp. PRwf-1, Iamia majanohamensis, respectively) commonly presented in all litters and feces. Real-time PCR results showed that the number of Escherichia coli in duck feces was significantly higher than that in D4 and D8 litters (P<0.05), while no significant difference was observed between duck feces and D0 litter (P>0.05). [Conclusion] Both the application time of bio-bed and duck feces origin microorganisms can affect the bacterial community and the number of E. coli in the bio-bed, and the bacterial community structure tends to be stable in line with the application time of the bio-bed.

Abstract:[Objective] The purpose of the present study was to investigate the phosphate-solubilizing ability of a bacterial stain BS06, for developing and applying effectively phosphate-solubilizing microbes in sugarcane production in Guangxi. [Methods] 16S rRNA gene sequence homology comparison, recA gene analysis as well as morphological, physiological and biochemical analyses were carried out to identify the bacterial strain BS06. The phosphate-solubilizing ability of BS06 was investigated under the conditions of changing the carbon and nitrogen source, separately in inorganic phosphate medium. [Results] The strain BS06 was identified as Burkholderia cepacia. The strain had high and efficient phosphate-solubilizing ability under the condition of carbon source with lactose and nitrogen source with sodium nitrate separately, and the concentration of water soluble phosphorus in fermentation solution was 262.71 mg/L and 305.85 mg/L, respectively. Compared with the uninoculated controls, BS06 significantly increased dry weights and phosphorus contents of micropropagated sugarcane seedlings. [Conclusion] The bacterial strain BS06 had high potential of exploitation.

Abstract:[Objective] The objectives were to characterize growth temperature of six Taifanglania strains and to determine the effect on straw degradation. [Methods] Temperature-growth of six Taifanglania strains was monitored by colony diameters at different temperatures. The aniline blue method and guaiacol method combined with degradation of calcium lignosulfonate were used to test their lignin-degrading capability. Hydrolysis spot diameter measurement method of CMC-Na and extracellular enzyme activity were employed to conjecture cellulose-degrading capability of strains. Then the effect on straw degradation was obtained through weight loss method and Van-Soest detergent. [Results] The tested thermotolerant fungi, Taifanglania spp. could grow at high temperature of 50 °C and produce cellulase. However, the lignin-degrading enzymes produced by different Taifanglania strains had some diversities. They were straw-degrading fungi, and T. hechuanensis H08.1 had higher capability than others, followed by T. cinerea H57.1, with straw degradation rates of 50.2% and 42.2%, respectively. [Conclusion] T. hechuanensis H08.1 and T. cinerea H57.1 exhibited tremendous potential for straw degradation.

Abstract:[Objective] The contribution of DNA-binding membrane protein (Dbp) to the virulence of Streptococcus suis 2 was evaluated by constructing a gene knock-out mutant of Dbp. [Methods] The distribution of Dbp was analyzed by PCR. An isogenic Streptococcus suis 2 mutant of Dbp, ?Dbp, was constructed based on the principle of homologous recombination, and the biological characteristics, pathogenicity of ?Dbp and wild type ZY05719 was compared. [Results] The Dbp gene may be a relatively conserved in different source of Streptococcus suis 2. Compared with wild type ZY05719, the growth rate of ?Dbp is significantly slower in the logarithmic phase, and the capsule of ?Dbp is different from wild type ZY05719. Zebrafish pathogenicity test showed that the LD50 of ?Dbp had a significant decrease as compared with wild type ZY05719. [Conclusion] Dbp gene is critical for the full virulence of Streptococcus suis 2. All these help us to understand its pathogenic mechanism.

Abstract:[Objective] A halotolerant bacterium LG was isolated from Yuncheng Salt Lake, and its identification and antimicrobial properties were studied. [Methods] The strain LG was identified by 16S rRNA gene sequence analysis. Using Staphylococcus aureus as the indicator, antimicrobial activity of the fermentation broth of strain LG was detected by cylinder plate method. Morphological and ultrastructure changes of treated cells were observed by scanning electron microscopy and transmission electron microscopy. Different physicochemical factors on its activity and PCR screening of functional genes were also studied. [Results] The strain is a halotolerant bacterium which can grow well over a range of NaCl concentration of 0-25%, and it is characterized as the genus of Bacillus and named as Bacillus sp. LG. Electron spectroscopy showed that significant morphological and ultrastructure changes of Staphylococcus aureus were observed after treatment by fermentation broth of Bacillus sp. LG. Antimicrobial properties of the strain LG indicated that it showed excellent stability towards temperature, ultraviolet, pH and NaCl. Using specific primers, polyketide synthase (PKS I) and nonribosomal peptide synthetase (NRPS) genes were detected by PCR technique, which indicated that the strain LG possess potential of producing active metabolites. [Conclusion] Results from the present study showed that microorganisms from extremophilic environment may be developed as a potential new source of antimicrobial substances.

Abstract:[Objective] In acarbose producing strain Actinoplanes sp., treY, an important gene in trehalose synthesis, encodes an enzyme that catalyzes acarbose to produce component C during the fermentation. However, component C impacts the quality of acarbose products terribly. In current study, we construct a genetically engineered strain with reduced component C. [Methods] An in-frame knock-out plasmid pUAmT-YUD is constructed and transformed into acarbose-producing strain Actinoplanes 8-22 to inactivate treY by homologous recombination. [Results] Fermentation tests showed that component C produced by the recombinant strain Y810 was reduced by about 10-fold comparing with the parent strain, while the titer of acarbose was not affected. [Conclusion] Knockout of treY leads to compound C decrease in acarbose fermentation. The application of this trial will simplify the purification steps, improve the acarbose quality and reduce the cost to some extent. In addition, conjugation conditions of Actinoplanes are optimized and the conjugation efficiency is improved notably.

Abstract:[Objective] The purpose of this study was to isolate and characterize an antagonistic bacterium against Fusarium on lily and to separate and identify its antifungal compounds. [Methods] Serial dilution method and dual-culture inhibition on agar plate were adopted for screening bacteria antagonistic to Fusarium oxysporum. The bacterial antagonists were rescreened by measuring siderophores-producing potential, hydrolytic enzymes activity and soil colonization. The previously isolated bacterial strain was identified using morphological, physiological and biochemical analyses as well as 16S rRNA gene sequencing. Antifungal substances produced by the antagonists were isolated, purified and analyzed based on bioactivity-guided method together with acid precipitation, flash chromatography and HPLC. [Results] A total of 64 bacterial isolates were obtained from the rhizosphere of filed-grown lily and 386 bacterial isolates were from marine organisms and silt. In a dual-culture inhibition test, 9 isolates displayed the antagonistic activity towards Fusarium oxysporum. Strain 11B91 was obtained by rescreening and identified as Bacillus amyloliquefaciens. Antifungal substances produced by strain 11B91 were speculated to be lipopeptides iturin and fengycin. [Conclusion] Strain 11B91 deserved to be developed a kind of biocontrol agent. This is to certify that bacteria from ocean could have potential for the biological control of pathogens which reside in soil so as to broaden our horizon for the?prevention and control of plant diseases.

Abstract:[Objective] This study aimed to screen and characterize antagonistic bacteria against Alternaria tenuissima, the causal agent of jujube shrinking fruit disease, and to study their antagonistic effects. [Methods] Serial dilutions and a dual culture technique were used for screening bacteria. The bacteria were identified based on morphological, physiological and biochemical features, and a phylogenetic analysis was conducted on an alignment of 16S rRNA gene sequences. Evaluation of the control activity and efficacy of fermentation filtrates against A. tenuissima was carried out by a dual culture assay, microscopic inspection and a spore germination test. Crude active proteins were separated by an ammonium sulfate method. [Results] Two strains of bacteria, STO-12 and STO-45, that were isolated and screened from the soil exhibited excellent inhibition against the fungal pathogen. Based on molecular, morphological, physiological and biochemical features, the two strains were identified as Bacillus subtilis. However, the two strains differed in the production of a pigment that was shorter in length in STO-12 than in STO-45. The fermentation filtrate, the supernatant and the cell-free filtrate of both strains exhibited excellent inhibition against the strain MY5 with a dual culture assay. Further effects of the cell-free filtrate of STO-45 on the pathogen included inhibition of germ tube and hyphal growth, and abnormally swollen or degraded hyphae and germ tubes. Crude active extracellular proteins of STO-45 isolated by an ammonium sulfate method proved to restrain the growth of hyphae. [Conclusion] Both STO-12 and STO-45 strains of B. subtilis have potential for the biological control of jujube shrinking fruit disease.

Abstract:[Objective] To provide a theoretical basis for the diagnosis and integrated control for the common bean pathogen. [Methods] This paper exploited the methods of conventional separation and Koch’s postulates to isolate and determine the pathogen of beans. Explicited it’s taxonomic status by combining morphological characteristics with ITS sequence analysis, and determined the ability of the pathogen to use carbon and nitrogen sources. [Results] The results showed that this pathogen mainly damaged pods, it would form round or nearly round brown, sunken spots on the pods surface, the pink mildew layer would appear on the lesion surface later; the conidium was obpyriform, single spore, hyaline, there was a diaphragm in the middle of the mature spores, the size was (6.23?12.42) μm×(12.07?24.67) μm. The rDNA-ITS sequence of the pathogenic fungus shared similarity was more than 99% with Trichothecium roseum (KC816070) that had reported. So, the pathogen was identified as Trichothecium roseum combined the morphologic characteristics with ITS sequence analysis. The grew rate of colony of Trichothecium roseum was fastest at the culture of maltose medium, and the growth on the medium of various carbon sources were faster than the control significantly (P<0.05); In the different nitrogen media, L-leucine could promote the growth of colony, but L-arginine and Urea had the significant inhabiting effects (P<0.05). [Conclusion] The results of this study had some reference value for the other plant diseases caused by Trichothecium roseum.

Abstract:Study on microbial metabolites is of great importance to the development of microbial pesticide. Recently, a series of Pseudomonas aeruginosa strains originated from plant rhizosphere have been isolated and identified. They performed well in biological control because of the antifungal metabolites produced. Here, an overview of the identified biocontrol strain Pseudomonas aeruginosa and their antifungal metabolites produced was provided. The latest progress in the biosynthetic mechanism of these antifungal metabolites and genetic engineering for industrial production was also introduced. Finally, the application of these antifungal metabolites in biological control and the prospects were briefly discussed.

Abstract:The researches on biological demulsifying bacteria have aroused widespread interests in oil exploitation and refining industry. However, the characteristics of demulsifying activities of biological demulsifying bacteria were not revealed owing to its complexity of mycelial morphology, surface properties and surface substances. In this paper, the classification, biosynthesis and demulsification mechanism of biodemulsifiers were introduced, and then the research progresses were reviewed focusing on the influence of mycelial morphology, surface properties and surface substances on the demulsifying activity. The research methods concerned in this field were specially focused. Based on the above analysis, the future research directions were proposed.

Abstract:Heme is the most abundant iron source in the host. It has been proven that heme was the main nutrient competition aim for the pathogenic bacteria, especially for the bacteria that is not able to synthesize heme. The heme acquisition system of Gram-negative bacteria is consist of hemophore, outer membrane heme receptor, TonB-ExbB-ExbD complex, periplasmic heme-binding proteins, ABC transporter and so on. Hemophore is a type of outer membrane or secreted protein that can extract heme from host hemoprotein and pass it to the outer membrane heme receptors. Up to date, three kinds of hemophores, HasA, HxuA and HmuY, have been identified in some Gram-negative bacteria. In this paper, we described the mechanism of these three types hemophore to capture heme and the interaction with outer membrane heme receptors in detail. It will be helpful for further understanding the function of hemophore and its working mechanism.

Abstract:Bacteroides fragilis is one of the symbiotic anaerobes within the mammalian gastrointestinal tract and is also an opportunistic pathogen which often isolated from clinical specimens. To provide reference for probiotic candidates screening, this article reviewed the pathogenicity and probiotic properties of Bacteroides fragilis, especially focused on the potential effects of Bacteroides fragilis as probiotics on prevention and treatment of diabetes and immune disease.

Abstract:Bacillus laccase is highly stable in alkaline pH and high temperatures. It is a typical representative of the bacterial laccase with high industrial application values. The best-studied bacterial laccase to date is the spore coat protein CotA from Bacillus subtilis. In recent years, many other types of Bacillus laccases have also been discovered. This review covered the recent burgeoning of Bacillus laccases, their catalytic properties, structural features, enzymatic properties and applications. Furthermore, the prospects of future research were also discussed.

Abstract:Consolidated bioprocessing (CBP), combining cellulose production, saccharification, and fermentation into one step, has been proposed as the most efficient way to reduce the production cost of ethanol from cellulosic biomass. Based on Saccharomyces cerevisiae surface display technology, cellulases are displayed on the cell surface using two approaches (1) noncomplexed cellulases, (2) multicellulase complex (cellulosome). The assembly of cellulosome on Saccharomyces cerevisiae has becoming a new hot spot in cellulosic ethanol CBP research because of its high cellulose hydrolytic activity than noncomplexed cellulases. In this paper, the basic structure of cellulosome and their applications in cellulosic ethanol production are reviewed. Also, the prospects of this research field are given based on our analysis of the problems that still have not solved by the previous studies.

Abstract:Ornithine is a non-essential amino acid. It plays key function to discharge amino nitrogen and solve ammonia toxicity. Recently, ornithine is widely applied in the fields of the function beverage, diet, health care, liver-protecting, anticancer, and in the food and medicine industry. With the utilization of microbial resources and application of metabolic engineering in strain improvement, microbial fermentation gradually becomes the major method of ornithine production. The biosynthesis metabolic pathway and catabolic pathways of ornithine, which key enzymes are involved in，are introduced in this paper. Furthermore, the author gives a detailed description about the way of which ornithine producing strain is reformed by the metabolic engineering, involving metabolic engineering technology and the recent research progress.

Abstract:Quorum sensing (QS), mediated by N-acyl homoserine lactones (AHL) and oligopeptides among various microbes in the dental plaque biofilm, maintains flora balance and severely affects dental caries, paradentitis and other oral diseases therapy. Currently, antibiotics are generally applied in treating these diseases. However, plaque microorganisms have significantly different sensitivity and tolerance to antibiotics. To circumvent the above disadvantages, host immune responses have to be considered in the dental therapy additionally, and to clarify plaque biofilm generation and the mechanisms of resistance, classification of signaling molecules and the quorum sensing formation related signal transduction system, inhibitors for plaque microbes and the perspectives were systematically summarized in this review.