Abstract:

Abstract:[Objective] In order to obtain an industrial strain with higher xylanase production, the original strain of Saccharomonospora viridis was mutated by atmospheric and room temperature plasmas. [Methods] The methods used to screen the mutant strain with higher xylanase production included transparent loop diameter measurement of selective medium with 2% beech-wood xylan and shaking flask fermentation. [Results] It has been demonstrated that both mutants AT22-2 and AT24 maintain good genetic stability. The enzyme activity in the fermentation liquor of AT22-2 and AT24 at 7 d reached 552.70 U/mL and 512.74 U/mL, which were 17 and 16 times higher than that of the original strain, respectively. Furthermore, the op-timum pH and temperature values for xylanase activity of AT22-2 were pH 9.5 and 90 °C, re-spectively, being stable within a temperature range of 50 °C?90 °C, and showing high thermo-stability at 100 °C for the duration of 30 min. In addition, for another mutant AT24, the opti-mum pH and temperature values for xylanase activity were pH 10.0 and 60 °C, with a stability within a temperature range of 60 °C?80 °C. [Conclusion] The xylanase with thermostability and alkali-tolerance of mutant AT22-2 is a potential candidate for future use in biotechnologi-cal applications particularly in the pulp and paper industry.

Abstract:

Abstract:[Objective] To improve laccase production and apply it to decolorize synthetic dyes, we made this research. [Methods] The nutritional and environmental conditions for laccase production were investigated. [Results] The optimum conditions described as follows: corn flour 20.0 g/L, potato starch 32.4 g/L, ammonium tartrate 2.9 g/L, Tween 80 0.5 g/L, CuSO4?5H2O 2.0 mmol/L, vanilline 0.54 mmol/L, NaH2PO4?2H2O 2.0 g/L, MgSO4?7H2O 0.5 g/L, MnSO4?H2O 0.1 g/L, inoculation concentration 8%, pH 6.0, liquid volume 40/250 mL, culture temperature 30 °C. [Conclusion] With the conditions, the activity of laccase was achieved at 35 U/mL, was higher 39 times than control. The laccase was applied to decolorize synthetic dyes and it was found that the laccase could decolorize azo dyes AR1 and RB5 rapidly which could be completed in 5 minutes.

Abstract:[Objective] In order to improve the production of succinic acid and decrease the accumulation of by-products under the oxygen deprivation by Corynebacterium glutamicum 13032. [Methods] From the C. glutamicum ATCC13032, firstly, the gene of lactic dehydrogenase (ldh) was knocked-out and the single deletion mutation strain C. glutamicum ATCC13032Δldh was constructed. Secondly, we interrupted the pathway of pyruvic acid flux to acetic acid by marker-free deletion the E1p gene (aceE) which encode the essential part of the pyruvate dehydrogenase complex (PDHC). [Results] The production and yield of succinic acid of recombination strain improved 94.9% and 32%, respectively, compared to the parent strain C. glutamicum ATCC13032 and what’s more, the main by-product lactic acid was eliminated to none from 63.5 g/L. The inactive of the pyruvate dehydrogenase complex could not prevent the formation of acetic acid absolutely, but the production of acetic acid decreased 37.9%, compared to C. glutamicum ATCC13032Δldh and the production of succinic acid improved a little. [Conclusion] This recombination bacteria has a potential in industrial applications, and this study methods could provide reference for microbial metabolism breeding.

Abstract:[Objective] Influence on corrosion behavior of copper in marine iron-oxidizing bacteria. [Methods] The effects of salinity and microbe on the corrosion behavior of copper were investigated by using open-circuit potential of electrode, polarization curves and electrochemical impedance spectroscopy (EIS). [Results] Results show that the analysis of scanning electron microscopy (SEM) indicated that the iron-oxidizing bacteria on the copper were rod. Electrochemical measurement results show that the control step for corrosion of copper in the culture medium for bacteria (IOB) in seawater is activation polarization process. The resistivity of seawater with bacteria is less 6 000 Ω·cm2 than that of without bacteria. It indicated that the retardation of the copper dissolution reaction in seawater with iron-oxidizing bacteria is small. [Conclusion] The presence of micro-organism (IOB) decrease the open circuit potential and activation polarizability of copper, thus speed up the corrosion process of pure copper.

Abstract:[Objective] This study is aimed to isolate and identify a strain which can produce dextranase, characterize the enzyme properties and study its application in Streptococcus mutans dental biofilm. [Methods] The strains derived from marine environment were screened by observing transparent circle on agar plates. The strains were identified by morphology, physiological characteristics, and phylogenetic analysis based on 16S rDNA sequences. The inhibitory effect of the dextranase on Streptococcus mutans dental biofilm was assessed with biofilm models in vitro. [Results] A dextranase-producing strain KQ11 was isolated from sea mud and preliminarily identified as Arthrobacter sp.. The optimal growth conditions of the strain were 30 °C, pH 7.5, and NaCl concentration of 0.4%. The optimal catalytic conditions of the enzyme were 45 °C, pH 5.5. The dextranase effectively prevented the dental biofilm formation by Streptococcus mutans. [Conclusion] The dextranase from the strain KQ11 can effectively degrade Streptococcus mutans dental biofilm, and thus it can be added to the oral care products such as mouthwash.

Abstract:[Objective] We investigated the composition and diversity of endophytic bacterial in Taxus chinensis. [Methods] The composition and diversity of endophytic bacterial in Taxus chinensis were analyzed by culture-independent method. When total community DNA were extracted, a pair of bacterial PCR primers were used for endophytic bacterial 16S rDNA gene amplification and a clone library was constructed for the Taxus chinensis DNA samples. Positive clones were analyzed by PCR restriction fragment length polymorphism (PCR-RFLP) and the clones with unique patterns were selected for sequencing and constructing 16S rRNA gene phylogenetic tree. [Results] Based on Hae Ⅲ digestion and sequencing result, a total of 158 positive clones that randomly screened from the library were fall into 26 operational taxonomic units (OTUs). These clone squences were divided into 4 phyla with phylogenetic analysis, which consisted of Alpha, Beta, Gamma and delta subclasses of the Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes, of which Proteobacteria accounting for 58.86% of the total number of clones was the absolutely dominant group. Sequence alignment showed these clone sequences have high similarities with 20 genus that had been reported. In addition, one OUTs on phylogenetic tree is independent and failed to determine its classification. [Conclusion] Taxus chinensis harbors a diversity endophytic bacterial and maybe existence new taxon.

Abstract:[Objective] The study was to clone, express the gene of chicken antimicrobial peptide fowlicidin-2 and characterize its bioactivity. [Methods] The gene encoding fowlicidin-2 with the condon preference of E. coli was designed based on the amino acids of fowlicidin-2 and synthesized in vitro. The gene was ligated into the plasmid pET32a, and transformed into E. coli BL21(DE3). The transformant E. coli BL21(DE3) was induced by IPTG. Cyanogen bromide (CNBr) was used to cleave the inclusion body of fusion protein and molecular sieve chromatography was used to purify the released fowlicidin-2. Bioactivity of the recombinant fowlicidin-2 was tested. [Results] The fowlicidin-2 fusion protein was expressed as inclusion body. Fowlicidin-2 was effectively released after digestion of the fusion protein with CNBr. The recombinant fowlicidin-2 exhibited high antibacterial activity against the Gram-positive and Gram-negative bacteria. [Conclusion] Fowlicidin-2 was successfully expressed in E. coli. The study provides theoretical foundation and technical means for scale-up preparation of antimicrobial peptides by engineering method.

Abstract:[Objective] Researched the diversity and distribution characteristics of endophytic fungi in Nicotiana tabacum in Dali District. [Methods] These strains were identified into genera based on morphological characteristics combined wtih ITS-rDNA gene sequences. [Results] A total of 1 586 strains of endophytic fungi were isolated from the leaves of Nicotiana tabacum and were identified into 31 genera. Alternaria and Fusarium are dominant fungal endophytes, occupying 40.79% and 18.73%, of total isolated strains respectively. [Conclusion] The quantity, diversity and distribution of the endophytic fungi were varied from different part leaves and different districts of N. tabacum. Larger quantity of endophytic fungi was found in lower part leaves than that of the upper ones. Otherwise, richer diversities of endophytic fungi were found in upper leaves. Along with the development of N. tabacum, the richness and diversity of endophytic fungi in N. tabacum leaves were increased and reached the largest during the squaring stage and maturity stage.

Abstract:[Objective] This study is aimed to isolate and characterize feather-degrading bacteria from soil, and to determine the optimal temperature and initial pH for growth and further to observe the dynamic of enzyme activity. [Methods] Serial dilution on agar plate and selective medium culture techniques were used for screening bacteria. Strain identification was based on phylogenetic analysis of 16S rRNA gene sequence and Biolog analysis. Optimal growth con-ditions were measured by automated microbiology growth curve analyzer. The proteolytic ac-tivity assay was carried out to observe the dynamic of enzyme activity. [Results] A feather-degrading bacterial strain, designated as GIMN1.015, was isolated and screened from the soil mixed with feathers. The strain was preliminarily identified as a strain of the genus Sporosarcina. The optimal pH and temperature for growth were 9.0 and 30 °C, respectively. The peak value of proteolytic activity appeared at 96 h of incubation time. [Conclusion] Strain GIMN1.015 has the potential for the application of feather keratin sources. This is the first report on the feather degrading by Sporosarcina.

Abstract:[Objective] In order to improve the inhibitory rate of fermentation broth of Streptomyces bikiniensis strain HD-087 against Fusarium oxysporum strain HU-M, the shake-flask fermentation conditions of biocontrol agent HD-087 were optimized. Restraining effectiveness of broth towards HU-M has been tested at the same time. [Methods] The liquid fermentation medium and conditions of HD-087 were optimized by single factor experiments and orthogo-nal experiments. After inoculation with broth, HU-M hyphae morphology and germination of conidia were then examined under the light microscope, and the relative conductivity of HU-M hyphae was measured using a conductivity meter. [Results] The composition of the optimal medium was 1.00% (W/V) starch, 0.80% (W/V) soybean flour, 0.12% (W/V) yeast extract, 0.40% (W/V) CaCO3. The optimal fermentation conditions were the combination of temperature 28 °C, initial pH 6.8, 180 r/min, incubation time 5 d, 1 mL inoculum volume and medium volume 40 mL/250 mL. The result of antibacterial effect can be concluded as follows: abnor-mality of pathogen hyphae and leakage of cytoplasm after treated with broth; meanwhile the inhibitive rate to conidia germination reached 72.1% when the broth diluted by 5 times. In ad-dition to that, exosmosis of hyphae content, conductance rate increased. [Conclusion] All these changes indicate that optimal shake-flask fermentation conditions can improve the in-hibitory activity of HD-087 broth against F. oxysporum HU-M, and the broth has been proved efficient for suppression of HU-M by severely destroying cell membrane structure, it’s of great potential application value.

Abstract:[Objective] Screening strains with 1-aminocyclopropane-1-carboxylate (ACC) deaminase and exploring the growth promoting effect were conducive to further develop microbial fertilizers and increase agricultural yield. [Methods] ACC deaminase positive bacteria were enriched and isolated with ACC as the sole nitrogen source. These strains’ ACC deaminase activities were also evaluated. The strain with the highest enzyme activity was identified according to morphological, physiological-biochemical characteristics and 16S rDNA sequences analysis. The target strain’s ability to promote the growth of alfalfa seedlings was preliminarily studied. [Results] Six ACC deaminase positive strains were obtained. Among them the strain ACC 30 was prominent with high ACC deaminase activity 0.217 U/mg. Based on the cultural morphological features as well as physiological-biochemical parameters in combination with 16S rDNA sequences analysis, the strain ACC 30 was identified as Enterobacter aerogenes. The growth-promoting trial indicated that both seeds incubating with bacterium suspension (SIBS) and seeds dipping with bacterium suspension (SDBS) elongated the roots of alfalfa seedlings by 135%, 136% respectively compared with the control group. The growth-promoting effects under two treatments were equally significant and consistent. Inter-estingly, they all showed that ACC 30 strain prohibited hypocotyl elongation. [Conclusion] The isolated strain ACC 30 with high ACC deaminase activity was expected to be developed into an excellent microbial fertilizer.

Abstract:[Objective] Study on the technology of selection and optimization of Bacillus natto freeze-dried powder, in order to increase the survival rates of living bacteria. [Methods] Single factor and orthogonal experimental designs were taken to measure the survival cells and then screened the protection agent formulations. And the storage stabilities of optimized lyoprotectant powder prepared at protection agent formulations. And the storage stabilities of optimized lyoprotectant powder prepared at ?20 °C, 4 °C and 25 °C were tested. [Results] The effective protecting agents of Bacillus natto were: skimmed milk powder, mannitol, L-sodium ascorbate. The best protectants formula: 10% skim milk powder, 4% Mannitol and 1% L-sodium ascorbate, the results showed that the survival rate could reach to 91.63%. The survival rates of fungus powder conserved at ?20 °C, 4 °C, 25 °C for 12 months were 88.79%, 70.16% and 10.52%, respectively. The storage stability of bacteria powder at ?20 °C and 4 °C were excellent, while that at 25 °C was poor. [Conclusion] The freeze-dried powder protective of Bacillus natto was optimized, which provided a guidance for application of Bacillus natto, stabilization of quality of live bacterial product and development of novel live bacterial products.

Abstract:[Objective] The purpose of this research was to analyze the biological characteristics of isolates NM1108-1 and NM1108-5 obtained from gadfly in China, and to determine the taxonomy of the two isolates. It provided more information about interaction between spiro-plasma and their host. [Methods] The gadfly spiroplasmas were isolated and cultured by con-ventional methods. Dark field and transmission electron microscopy were used to examine the morphology and movement of spiroplasma isolates. The taxonomy of the two isolates was evaluated according to their biological and phylogenetic characteristics. [Results] A large number of spiroplasmas were isolated from gadfly, and two representative strains NM1108-1, NM1108-5 exhibited helical form in logarithmic phase. Both the spiroplasmas from gadfly could use glucose, sucrose and D-fructose as a carbon and resisted to penicillin, but did not hydrolyse urea or arginine. The phylogenetic analysis based on 16S rDNA and ITS sequences showed that both isolates NM1108-1 and NM1108-5 belonged to the Apis clade but were di-vided into two different branches. NM1108-1, NM1108-5 were clustered into S. turonicom, S. gladiatoris respectively. [Conclusion] The isolates of NM1108-1 and NM1108-5 were initially determined as S. turonicom and S. gladiatoris respectively according to their biological and phylogenetic characteristics. This was the first report about the spiroplasmas from gadfly in China.

Abstract:[Objective] In order to cultivate high concentration of bacteria to deal with algal blooms caused by water eutrophication of algal blooms quickly. [Methods] Firstly, three important factors: KNO3, MnSO4?H2O and K2HPO4 which played important roles in NP23 bacteria concentration were selected based on the Plackett-Burman (PB) design experiments. Then, the best value of the selected important factors was picked out using response surface methodology (RSM) to optimize the process conditions of NP23. At Last, biological safety of NP23 bacteria liquid was evaluated by the acute toxicity and mutagenicity test. [Results] The bacteria concentration got 1013 CFU/mL after optimization, which were four orders of magnitude more compared with bacteria concentration before optimization and which showed that NP23 had no poisoning effect and no mutagenic effect on fish even in large doses. [Con-clusion] The results provide reference to practical applications of NP23.

Abstract:[Objective] To understand the field of microbial oil displacement mechanism, evaluation standards and its influence factors. [Methods] The growth, migration and distribution law of microbes during microbial displacement oil were studied based on site tracing monitoring during field microbial displacement oil and the physical model experiment in laboratory. [Results] The results show that the exogenous microbes injected from water injection well can grow and reproduce well in oil reservoir, and the injected nutrient solution is also capable of activating indigenous microbes, but the microbes concentration in produced fluid is lower 1?2 orders of magnitude than injected microbes concentration due to the formation permeability and nutrient concentration. Because of the rapid glucose degradation and the microbes filtration and adsorption by formation, the amount of microbes stay near the wellbore and only part of them can be produced from the corresponding oil well. Moreover, the migration rate of microbes is slower than nutrition. [Conclusion] The formation permeability and the nutrient concentration of output liquid are the two key factors on microbial quantity. The microbes concentration in produced fluid is difficult to exceed 106 cells/mL on site. The results of the study have a great significance for the development and application of microbial displacement oil technology.

Abstract:Acidithiobacillus spp. is important for bioleaching because of the copper-resistance mecha-nism. Many data suggest that Acidithiobacillus spp.’s tolerance to copper is much higher than common bacteria. In the present paper, we reviewed the current knowledge on cop-per-resistance mechanism in Acidithiobacillus spp., including: eliminating copper from the cytoplasm of the cells; reducing copper concentration in the periplasm; a polyphosphate-based copper-resistance system; a newfound genomic island and an oxidative stress response gener-ated by copper. Furthermore, we discussed methods in transcription-regulation and pro-tein-function, to address future research needs.

Abstract:Chlamydia plasmid is a 7.5 kb, highly conserved, non-integrative DNA molecule present in almost all strains of Chlamydia trachomatis, as well as Chlamydia muridarum and Chlamydia psittaci. Recently, Chlamydia plasmid has been considered to be a virulence factor which contributes to mouse oviduct hydrosalpinx. Studies in animal models indicate that plasmid-deficient Chlamydia strains function as live attenuated vaccines against genital and ocular Chlamydia infections. Nevertheless, Chlamydia plasmid is also a potential genetic manipulation tool for revealing Chlamydia trachomatis pathogenic mechanism. Therefore, research on Chlamydia plasmid is very meaningful.

Abstract:The effect of Bacterium Gram stain is influenced by many factors. In our class the teaching efficiency was significantly improved with the application of inquiry-based teaching, through which the key factors of fixed patterns and decoloration time were systematically designed and the difference was presented visually. Under the driving forces of intrinsic curiosity and specific assignments, moreover, the many performances of students, such as initiative consciousness, thinking traits, problem-solving ability, team spirit, were stimulated and cul-tured during the inquiring process. Practically, the problem-oriented experimental design not only strengthens the skill and enhances the teaching efficiency, but also mobilize the enthusi-asm, stimulate the initiative consciousness and culture the scientific thinking traits.

Abstract:Designing experiments of Microbial Pharmaceutics play an important role in improving students’ quality and cultivating students’ ability. To improve the teaching quality, PBL (problem-based learning) is applied. The introduction of PBL significantly enhances students’ learning initiative, practices students’ ability to analyze and solve problems, and nurtures the team spirit. In this article, the implementation of PBL in designing experiments and personal views derived of this process are reported.

Abstract:[Objective] The contamination of Enterococcus faecalis in source water, activated carbon filtered water and finished water from mineral and spring water plants in Guangdong province was investigated for offering important data to control the E. faecalis pollution. [Methods] The standard GB/T8538-2008/4.53 with little modification was used to detect the existence of E. faecalis, then to carry out the ERIC-PCR fingerprinting of E. faecalis. [Results] Thirty-five samples were detected positively for E. faecalis with the total contamination rate of 17%. Among the 35 positive samples, the source water, activated carbon filtered water, and finished water samples were 20 (26.3%), 13 (20%) and 2 (3.1%) respectively. According to ERIC-PCR, E. faecalis strains from 35 samples were divided into three groups and the type B was the main genotype in Guangdong province. [Conclusion] The results indicated that the contamination rate of E. faecalis in spring water in Guangdong province was much higher than that of mineral water, moreover, as far as spring water was concerned, the source water contamination rate was higher from surface water than from ground water.

Abstract:[Objective] Potyvirus is one of the largest plant virus genus, causing significant losses in a broad range of host. We give an objective analysis of the development trend on Potyvirus in worldwide by bibliographic database, provide a reference for Potyvirus scientists and policy makers, and promote Potyvirus research work. [Methods] Based on Web of Science database, the countries, the authors, institutions, papers journals and research area of the Potyvirus literature published in 1985?2012 all over the world, are carried out quantitative and qualitative analysis. [Results] The number of Potyvirus documents published were totally 2 442 from more than 60 countries. At the same time, each literature citation frequency and the H index of every country, institution or the author were retrieved. The output of the Potyvirus research papers in worldwide was a steady upward trend since 1991. According to the quantity and quality of literature in the statistics, the United State was the best, followed by France, Spain, Australia and England. There were more core authors in the United States. The research hotspot in Potyvirus was the gene silence and molecular biology, and the research area tend to viral host (such as gene silencing, host resistance, the interaction virus-host) and interdiscipli-nary. There is a great distance between China and the international advanced level, including less research efforts and the less high papers. [Conclusion] The United States in the research field is at the top. China need to put more efforts to shorten the gap.