Abstract:

Abstract:One hundred and five endophytic actinomycetes were isolated using four different media from surface-sterilized tissues of 7 plants samples of Alstonia scholar collected from Xishuangbanna Yunnan province, southeast China. The results showed that they belong to 9 genera, 7 families by 16S rRNA gene sequences analysis. All actinomycete strains fermentation liquids were carried out the antimicrobial activities test against five plant pathogenic fungi. The results showed that 12.4%, 14.3%, 11.4%, 12.4%, 8.6% endophytic actinomycetes presented antimicrobial activity for Fusarium graminearum, Phytophthora nicotianae, Alternaria alternata, Colletotrichum gloeosporioides and Candida albicans, respectively. Three strains with strong antibacterial activities were refermented and rescreened, their antimicrobial activities were stability, and may produce alkaloids.

Abstract:

Abstract:It is a common method that hemicellulose of corncob was hydrolyzed by dilute sulfuric acid to obtain hemicellulose hydrolysates. However, the hydrolysates of hemicelluloses contain not only xylose but also some inhibitors such as furfural, acetic acid and various phenol compounds. Based on the combination of multiple detoxification methods, the effect of activated charcoal in detoxification procedure was studied. The results showed that the activated charcoal GH-13 and GH-15 were effective for detoxification of the hydrolysate. The more the activated charcoal charge, the less the content of inhibitors in the hydrolysate, but the more xylose loss. GH-15 of 5% (W/V) was best for detoxification of the hydrolysate and acetic acid of 24.60% and furfural of 100% were removed in the condition, the R280 was 0.009, which stands for removal of phenolic compounds in hydrolysates, but xylose of 23.70% was lost in the process.

Abstract:A novel poly β-hydroxybutyrate (PHB)-accumulating bacterium, strain SCH17, was isolated from soil samples by butanol enrichment. A phylogenetic analysis based on 16S rRNA sequence data indicated that the strain SCH17 was a member of the genus Pseudomonas. Transmission electron micrographs showed electron-transparent intracellular granules. The purified sample was extracted from cells with chloroform and was determined as PHB by nuclear magnetic resonance analysis. Pseudomonas sp. SCH17 was able to accumulate PHB after growth on various carbon and nitrogen substrates. Fructose and fish peptone were the optimal carbon source and the optimal carbon source, respectively. After grown under the optimal conditions for 14 h, the maximum cell dry weight of 3.52 g/L with the PHB concentration of 2.69 g/L was obtained, and the PHB content was up to 76%.

Abstract:In order to enhance the concentration of ε-polylysine (ε-PL) with Streptomyces albulus ZC7, response surface methodology were used to optimize the fermentation medium. A Plackett-Burman design was used to evaluate the influence of eight factors firstly. Results showed that the concentration of glucose, yeast extract and (NH4)2SO4 played important roles in influencing the content of ε-PL. Then, the path of steepest ascent and the Box-Behnken design were adopted for further optimization, and the optimum concentration levels and the relationships among these factors was found out by quadratic regression model equation with Design-Expert statistic methods, the optimal concentration of the variables were determined as: glucose 37.22 g/L, yeast extract 6.9 g/L, (NH4)2SO4 6.55 g/L. Under such conditions, the concentration of ε-PL was increased to 8.11 g/L, which was 24.6% higher than the maximum value in the single factor tests.

Abstract:The nitrite reductase type of Rhodopseudomonas palustris strain 2-8, a denitrifying bacteria, was identified by polymerase chain reaction (PCR) and bioinformatics analysis as Cu-containing nitrite reductase (CuNiR). The gene encoding Cu-containing nitrite reductase, nirK, has been cloned and sequenced. The nirK gene was 1 154 bases in length and has significant identity with the nirK sequences of Rhodopseudomonas palustris TIE and Rhodopseudomonas palustris CGA009, their identity were both 90%, and it has been deposited with the GenBank Data Libraries under accession number GU332847. Bioinformatics analysis showed it coded a protein consisting of 370 amino acids, this protein was a kind of Cu-containing dissimilatory nitrite reductase, and it was stable, pI 6.2, located in periplasmic or out of membrane, composed of alpha helix, extended strand, random coil and ambigous states. There were four 2Fe-2S ferredoxin-type iron-sulfur binding region signatures and one 4Fe-4S ferredoxin-type iron-sulfur binding region signature. Northern hybridization result showed this nirK gene presented as a single copy and has been transcripted in the cell of Rhodopseudomonas palustris 2-8.

Abstract:To obtain the algicidal components from actinomycete strain L74, a series of techniques including centrifugation, ethanol precipitation, organic solvents extraction, silica gel adsorption chromatography, dialysis and chemical analysis were used. In addition, we studied the characteristic of stabilities of algicidal components under different pH and temperatures, and the influence of it to anti-oxidation enzyme system of Microcstis aeruginosa. The results suggested that the algicidal components may be or contain glycosides, lactones and triterpenes, which the molecular weights are less than 3.0 kD. In extraction experiments, petroleum ether, acetic ether and n-butanol can efficiently separate the algicidal components into water-layer. The algicidal components are stable for pH, but sensitive for temperature. After treated under 90 °C for one hour, the activity is nearly lost. When cultivated with algicidal components, the MDA contents of Microcstis aeruginosa increase and maintain at a high level, but the activities of SOD, POD and CAT significantly increase in the early cultivation and decline quickly in the late stage.

Abstract:The reduction and detoxification mechanism of sodium selenite by Rhodopseudomonas palustris were studied in this paper. Effect of factors on the reduction and detoxification of sodium selenite based on a single-factor test and orthogonal experiment were investigated. Results showed that selenite removal rate by the reduction and detoxification of Rhodopseudomonas palustris were achieved at 98.2% under optimal conditions with concentration of sodium selenite at 25 mg/L, 15% of inoculums amount (W/W) and cultivation for 5 days. The researches indicated that selenite reductase with the molecular weight of 182 kD was composed of four subunits polymers and distributed in cytoplasm. Reducing selenite into selenium particles with diameter in 5 nm?200 nm during reduction and detoxification of Rhodopseudomonas palustris were also primarily identified by transmission electron micrograph.

Abstract:The growth pattern of the bacteria and degradation characteristics of the crude enzyme extracted from an isolated strain Bacillus cereus HY-1 were approached in the paper. The results showed that the adaptation period of the bacteria was prolonged by addition of chlorpyrifos and the logarithmic phase and stationary phase were also extended against the control. Moreover, the pH of the culture medium increased with the growth of the strain. The results also indicated that the soluble protein of the crude enzyme was determined with Albumin (bovine serum) as standard protein and the soluble protein content of the crude enzyme was 2.21 g/L. The Km value and the maximal enzymatic degradation rate for chlorpyrifos were 1.235 6 mmol/L and 0.022 6 μmol/(mg·min), respectively. The appropriate incubation time for the enzymatic degradation was 1 h. The highest specific activity of the crude enzyme was gained when the adding volume of the crude enzyme was 1 mL. The crude enzyme activity had optimal temperature of 28 °C for the enzymatic degradation of chlorpyrifos, which was still over 78% of the maximal activity within temperature ranged from 20 °C to 44 °C. The crude enzyme showed comparatively greatest enzymatic activity at pH 6, high activity pH ranged from 5 to 9. Furthermore, additional experimental evidence revealed that the crude enzyme had some extent stability for temperature and pH. The crude enzyme also degraded chlorpyrifos efficiently while it was dealt with sodium chloride from 10 g/L to 70 g/L for 1 h.

Abstract:Both culture-dependent and culture-independent methods, denaturing gradient gel electrophoresis (DGGE) based on the sequence of 16S rDNA, were used to examine the microbial quantity, bacterial community structure and diversity in different soil types (Peat soil, Swamp soil, Meadow soil and Sandy soil) and soil detphs (0?20 cm, 20 cm?40 cm and 40 cm?60 cm) under different stages of degradation in Zoige Wetland. Experimental results showed that total microbial quantity decreased with the soil types (Peat soil>Meadow soil>Swamp soil>Sandy soil) and declined with soil depths (0?20 cm>20 cm? 40 cm>40 cm?60 cm). Bacterial community structure was affected by soil type more primarily than by soil depth. Bacterial community diversity generally declined with soil types (Peat soil>Sandy soil>Meadow soil>Swamp soil). However, no significant tendency was found for the soil depth. In addition, the total microbial quantity was strongly correlated with organic matter, total nitrogen and pH, and bacterial community diversity exhibited significant negative correlation with pH. Ten bands were excised from the DGGE gel and re-amplified for 16S rDNA sequencing. Based on the sequencing results, seven bands can be identified as related to γ-Proteobacteria, one close to α-Proteobacteria, and the other two belong to Bacteroidetes. These results provide evidence that Proteobacteria are the domain bacterial communities in the soil of Zoige Wetland.

Abstract:The actinomycete strain SCY311, which exhibited antifungal activity against various plant pathogenic fungi, was isolated from the soil samples collected from Fenghuang Mountain in Henan province in China. Identification of strain SCY311 was conducted by the methods of traditional and molecular biological taxonomy, including determination of morphological characteristics, cultural characteristics, physiological and biochemical properties, cell wall components and 16S rRNA sequences analysis. Results showed that strain SCY311 grew well on Gause′s synthetic agar plate. The color of substrate mycelium appeared brown, while that of aerial mycelium went from gray to mouse gray. The strain SCY311 neither produced the soluble pigment nor exhibited hygroscopicity. Spores were arranged in coil chains and the branched spore chains formed open or closed spirals. Spores were oval or columned in ship and the spore wall ornamentation category was knobby. Physiological properties and cultural characteristics of the strain SCY311 on the ISP media were in close agreement with that of the Streptomyces torulosus. The 16S rRNA gene sequence of strain SCY311 showed 99.9% similarity to that of S. torulosus. Based on the results above, the strain SCY311 was identified as S. torulosus.

Abstract:△6-desaturase plays an important role in the biosynthesis of γ-linolenic acid in Mucor sp. EIM-10. To improve enzymatic activity and confirm the effect of primary structure on the △6-desaturase activity, a random mutation library was constructed. The △6-desaturase gene (mcd6, GenBank accession No. EU717846) was mutated by error-prone PCR strategy. The PCR products were ligated into the yeast expression vector PYMD6PMCD6. The resulting plasmid was named PYTBMCD6 and transformed into Saccharomyces cerevisiae strain INVSc1. A random △6-desaturase gene mutation library was constructed in Saccharomyces cerevisiae. The titers of random mutation library were up to 4.6×104 CFU. The random mutation library of △6-desaturase gene could be used for screening the mutants with change in catalytic activity and the subsequent site-directed mutagenesis.

Abstract:Hydrogenases of chemolithoautotrophic bacteria play important roles in material and energy transfer in deep-sea hydrothermal ecosystem. By designing PCR primers, a hynL gene encoding large subunit of membrane-bound group I NiFe hydrogenase from Caminibacter profundus was cloned and bioinformatively analyzed. The relative expressions of hynL, methyl viologen (MV)-reducing hydrogenase activities and bacterial growth in response to different H2 concentration were also studied. The results showed that a 864 bp hynL gene segment was obtained, predicted amino acid sequence had a 99% similarity with that of Lebetimonas acidiphila, and it belongs to the same phylogenetic branch with group I NiFe hydrogenase large subunit of hydrothermal chemolithoautotrophic Epsilonproteobacteria D group. Both hynL relative expression and MV-reducing hydrogenase activity reached the highest level at 12 h and 24 h respectively, when the strain was in the exponential growth phase. Sixty per cent of H2 concentration was optimal for hynL expression, MV-reducing hydrogenase activity and bacterial growth. All these results suggested that C. profundus regulates hynL expression in response to H2 changes in hydrothermal environment, thereby affecting the catalytic energy process, as well as the growth and propagation.

Abstract:A new fungus, designated GC2-2, which produced thermostable alkaline cellulase was isolated from deadwood soil. GC2-2 was identified as Cladosporium sp. by morphological characteristics as well as by analysis of the gene encoding the 18S rRNA. Cladosporium sp. GC2-2 produced cellulase enzyme. The enzyme activity on filter paper was higher than that on CMC. The optimal conditions for the enzymatic reaction were about 35 °C and at pH 7.5.

Abstract:In this study we aimed to evaluate the biocontrol efficacy of Bacillus cereus CH2 against Verticillium wilt on eggplant in field condition and its influence on rhizosphere microbial community structure. Based on the results we can make a conclusion that Bacillus cereus CH2 could reduce the desease incidence of Verticillium wilt on eggplant at 60.6%. The Biolog data showed that inoculating of CH2 had no significant impacts on the diversity of microbial community in rhizosphere. It also showed that its inoculation could increase utilizing ability of five groups of carbon sources except the phenolic compounds during the early growth stage of plants.

Abstract:Two bacteria strains marked AS and CS, producing 1-aminocyclopropane-1-carboxylate (ACC) deaminase, were isolated from wheat rhizosphere of drought soil. The activity of ACC deaminase from AS and CS strains was 0.018 6 U/mg and 0.016 7 U/mg protein, respectively. Based on the cultural morphological features as well as physiological and biochemical parameters in combination with 16S rDNA sequence analysis and sequence homology analysis, the strain AS and CS were identified as Enterobacter hormaechei and Serratia proteamaculans, respectively.

Abstract:A novel strain which could produce raw starch-digesting glucoamylase was isolated from Baoning bran vinegar Daqu and numbered as CQB43. Its raw starch-digesting glucoamylase activity was 105.2 U/mL and the RDA value was 27.9%. The species attribution of the strain was confirmed to be Absidia corymbifera by the characterization of morphological, and the similarity of the nucleotide sequence of the 26S rDNA gene and ITS region gene of the strain. Then the enzyme characters of the crude extracts produced by Absidia corymbifera CQB43 were studied. The optimum pH for the enzyme activity was 5.0, and it was very stable at the the pH range about 4.0-5.6. The optimum temperatures was 40 °C. Besides, the enzyme was very stable at the temperature of less than 60 °C, as its remnant activities was about 88% after 2 hours at 60 °C. According to the research on enzyme activity affected by metallic ion, it was activated by Co2+, whereas the activity was inhibited by Fe3+ and Ca2+.

Abstract:(R)-3-Quinuclidinol is an important chiral building block for the synthesis of a variety of pharmaceutical. A strain which is able to transforming quinuclidinone into reductase (R)-3-Quinuclid inol was isolated from soil by using quinuclidinone as sole carbon sourse in the screening medium. The physiological and bio-chemical identification and 18S DNA sequense analysis revealed that this strain belongs to Rhodotorula mucilaginosa and was named as R. mucilaginosa X15. The present results indicated that the optimal conditions for the transforming reaction with resting cells of R. mucilaginosa X15 were 3-quinuclidinone 10 g/L, pH 7.5, 30 °C and 72 h reaction time. (R)-3-Quinuclidinol is obtained with an yeild of 90% and with an optical purity of 88% enantiometric excess (ee) from a 100 mL reaction mixture.

Abstract:Exopolysaccharide from Rhizobium sp. N613 (REPS) was degraded by microwave irradiation with H2O2 to improve its physical, chemical and anti-tumor activity. Effects of REPS’s concentration, H2O2’s concentration, intensity and time of microwave irradiation on the molecular weight of degradated products were investigated by orthogonal test. Then the antitumor activities of four different molecular weight of LREPS were evaluated in mice bearing sarcoma 180. The results indicated that inhibition rate reached 52.8% when the molecular weight of LREPS reduced to 10.352 kD. LREPS(10.352 kD)’s preparation conditions were as follows: REPS’s concentration was 2 g/L, H2O2’s concentration was 6%, radiation intensity was 375 W, and irradiation time was 2 min. The molecular structure of the LREPS was analyzed by IR. The result indicated that LREPS was a β-glucan. The solubility of LREPS was increased from 8 g/L to 15.73 g/L, and the intrinsic viscosity of LREPS was reduced from 527.64 mL/g to 351.67 mL/g. The technology of preparing LREPS was established. Moreover, relevant technical parameters were obtained. Results of these study lay a certain foundation for the production and application of the polysaccharide.

Abstract:Nonylphenol polyoxyethylene (NPnEO) is a commonly used nonionic surfactant that can be found in all kinds of detergents and emulsifier. NPnEO has relatively low persistency in the environment; however, the great biological toxicity of NPnEO intermediate products cannot be ignored due to its widespread use. Bioremediation is an effective and economic method to repair the environment that has been polluted by NPnEO. So researchers have paid much attention on the point. Most of these researches focus on the isolation, identification and characterizing bacteria with abilities to degrade NPnEO. In the present study, a bacterial strain OPQa3 capable of utilizing NPnEO as sole carbon source was isolated from water samples collected from tannery waste treatment plant suffered long-time application of NPnEO by enrichment method. It was preliminarily identified as Brevundimonas sp. according to morphological characteristics, physiological-biochemical properties and the similarity analysis of its 16S rRNA gene sequence. The growth period of strain OPQa3 was 24 h. Inoculated 2% of OPQa3 solution, to give a final OD600 of approximately 0.70, to NPnEO solution that initial concentration was 746 mg/L, degradation tests showed that, the degradation rate of strain OPQa3 was 84.5% within 120 h, the optimum temperature is 30 °C while the optimum pH is about 7. At the same time, a plasmid strip was found from strain OPQa3 through plasmid detection. The experiment of plasmid elimination conformed that the plasmid has some relation to the ability of NPnEO degradation which is a degradative plasmid.

Abstract:The protein expression levels of Streptococcus pneumoniae D39 upon Levofloxacin treatment were studied using comparative proteomics method. In total, 23 differentially expressed proteins were identified via mass spectrometry. These proteins mainly involved in the DNA replication, transcription and protein translation. This study provides important information to the molecular mechanism of antibiotics actions and the drug resistance of bacteria.

Abstract:Iron acquisition represents a challenging problem for bacteria because Fe is an essential element with very low bioavailability. Siderophores, produced by microorganisms, are high-affinity ferric iron chelators with attractive structural diversity. Two main pathways for siderophore biosynthesis have been reported. One involves multifunctional metasynthase nonribosomal peptide synthetase (NRPS), while the other is NRPS-independent (NIS) and catalyzed by siderophore synthetase superfamily. Biosynthesis of siderophores has been the focus of inquiry for nearly twenty years. The enzymology of NRPS-mediated biosynthetic pathway of siderophore has been intensively studied and a vast knowledge of the NRPS-independent siderophore (NIS) biosynthesis is increasing. As siderophore is one type of the important secondary metabolites from actinomycetes, genetic and biochemical studies of its biosynthetic pathways will provide an opportunity to develop potential antibacterial agents, and enable the increasing understanding of the biosynthetic mechanism of this kind of natural products as well. Here we summarize the recent progress in mechanism of siderophore biosynthesis.

Abstract:The undergraduate tutorial system is a new cultivation pattern generated to suit the modern medical educational program, aiming at meeting the demands of students’ personality development and creative spirit, which overcomes, to a great degree, the shortcomings of traditional teaching patterns. By setting up the teaching theory of students becoming the leading actors and improving their comprehensive qualities as the core, the tutorial system brings students’ initiative and creativity into full play, enhances their practical skills and comprehensive qualities, and improves the teaching effect of medical microbiology, which deserves in-depth study and promotion.