Design, recombinant expression, and antibacterial activity of a novel hybrid magainin-thanatin antimicrobial peptide.

Antimicrobial peptides are small molecule polypeptides with biological activity, which can avoid the drug resistance. Magainin and thanatin are antimicrobial peptides with a broad spectrum of inhibitory microbes, and the core sequence of magainin is linked to a core sequence of thanatin. Here, the hybrid magainin-thanatin (MT) antimicrobial peptide was designed through bioinformatics analysis. The recombinant MT antimicrobial peptide was successfully expressed and purified in Escherichia coli BL21 (DE3). The molecular weight of the hybrid MT antimicrobial peptide was about 3.35 kDa. Moreover, the target protein indeed has an inhibitory effect on Staphylococcus aureus, E. coli DH5α, and Bacillus subtilis, with the minimum inhibitory concentrations 16.5, 20, and 9 µM, respectively. The rational designed hybrid MT antimicrobial peptide will hopefully provide large-scale fermentable antimicrobial peptides in the industrial production in the future.

Functional expression, purification, and antimicrobial activity of a novel antimicrobial peptide MLH in Escherichia coli.

In this study, a novel heterozygous antimicrobial peptide MLH was synthesized, expressed, purified, and characterized. The peptide Md-cec-LL-37_Hp (MLH) was selected through bioinformatic analysis using musca domestica antimicrobial peptide (Cec-Med), human antimicrobial peptide LL-37, and helicobacter pylori antimicrobial peptide (Hp) as parent peptides. The target gene was synthesized by overlap extension PCR (SOE-PCR) and connected to the expression vector pET-32a (+), and the recombinant plasmid pET-32a-MLH was transformed to Escherichia coli for constructing pET-32a-MLH/BL21 (DE3). Isopropyl ß-D-thiogalactoside (IPTG) was used to induce protein expression, and SDS-PAGE and western blot were adopted to test the target protein. And fermentation condition was optimized to get the mass expression of the fusion protein. The Ni2+ affinity chromatographic column was used to purify. Active heterozygous peptide was obtained after renaturation. Finally, the activity of the heterozygous antimicrobial peptide was identified. The fusion peptide showed significant antimicrobial effect on both E. coli and Staphylococcus aureus.

[Hydrogen and Oxygen Isotopic Compositions of Precipitation and Its Water Vapor Sources in Eastern Qaidam Basin].

Stable hydrogen and oxygen isotopes can be used as a tracer to analyze water vapor sources of atmospheric precipitation. We choose Golmud and Delingha as our study areas, Golmud locates in the south of Qaidam basin, and Delingha locates in the northeast. Based on the analysis of monthly change of hydrogen and oxygen isotopic compositions of precipitation during June to September of 2010, and the relationship between deltaD and delta18O in precipitation, we investigated the water vapor sources of precipitation in eastern Qaidam basin. The results show that: (1) meteoric water line between June to September in Golmud is: deltaD = 7.840 delta18O - 4.566 (R2 = 0.918, P < 0.001), and in Delingha is: deltaD = 7.833 delta18O + 8.606 (R2 = 0.986, P < 0.001). The slopes and intercepts of meteoric water line between June to September in both Golmud and Delingha are lower than the global average, and the intercept in Golmud is only -4.566, which indicates the extremely arid climate condition. (2) the delta18O content of precipitation is much higher in Golmud in early July, it shows the enrichment of some heavier isotopes. However, the delta18O content of precipitation becomes lower from late July to early September, especially for the late September. The 8180 content of precipitation in Delingha is higher in June to August than that in late September. (3) the water vapor sources of precipitation in Golmud and Delingha are different, Golmud area is the northern border of Qinghai-Tibet Plateau where the southwest monsoon can reach, and the southwest monsoon brings water vapors of precipitation, but the water vapors of precipitation in Delingha are mainly from local evaporation.

Enhanced Production of Epothilone by Immobilized Sorangium cellulosum in Porous Ceramics.

Epothilone, which is produced by the myxobacterium Sorangium cellulosum, contributes significant value in medicinal development. However, under submerged culture conditions, S. cellulosum will accumulate to form bacterial clumps, which hinder nutrient and metabolite transportation. Therefore, the production of epothilone by liquid fermentation is limited. In this study, diatomite-based porous ceramics were made from diatomite, paraffin, and poremaking agent (saw dust). Appropriate methods to modify the porous ceramics were also identified. After optimizing the preparation and modification conditions, we determined the optimal prescription to prepare high-performance porous ceramics. The structure of porous ceramics can provide a solid surface area where S. cellulosum can grow and metabolize to prevent the formation of bacterial clumps. S. cellulosum cells that do not form clumps will change their erratic metabolic behavior under submerged culture conditions. As a result, the unstable production of epothilone by this strain can be changed in the fermentation process, and the purpose of increasing epothilone production can be achieved. After 8 days of fermentation under optimized conditions, the epothilone yield reached 90.2 mg/l, which was increased four times compared with the fermentation without porous ceramics.

[Assessment on the changing conditions of ecosystems in key ecological function zones in China].

In this paper, the dynamics of ecosystem macrostructure, qualities and core services during 2000 and 2010 were analyzed for the key ecological function zones of China, which were classified into four types of water conservation, soil conservation, wind prevention and sand fixation, and biodiversity maintenance. In the water conservation ecological function zones, the areas of forest and grassland ecosystems were decreased whereas water bodies and wetland were increased in the past 11 years, and the water conservation volume of forest, grassland and wetland ecosystems increased by 2.9%. This region needs to reverse the decreasing trends of forest and grassland ecosystems. In the soil conservation ecological function zones, the area of farmland ecosystem was decreased, and the areas of forest, grassland, water bodies and wetland ecosystems were increased. The total amount of the soil erosion was reduced by 28.2%, however, the soil conservation amount of ecosystems increased by 38.1%. In the wind prevention and sand fixation ecological function zones, the areas of grassland, water bodies and wetland ecosystems were decreased, but forest and farmland ecosystems were increased. The unit amount of the soil. wind erosion was reduced and the sand fixation amount of ecosystems increased lightly. In this kind of region that is located in arid and semiarid areas, ecological conservation needs to reduce farmland area and give priority to the protection of the original ecological system. In the biodiversity maintenance ecological function zones, the areas of grassland and desert ecosystems were decreased and other types were increased. The human disturbances showed a weakly upward trend and needs to be reduced. The key ecological function zones should be aimed at the core services and the protecting objects, to assess quantitatively on the effectiveness of ecosystem conservation and improvement.

Mutation and a high-throughput screening method for improving the production of Epothilones of Sorangium.

The epothilones are highly promising prospective anticancer agents that are produced by the myxobacterium Sorangium cellulosum. We mutated the epothilone producing S. cellulosum strain So0157-2 to improve the production of epothilones. For evaluation in high-throughput of a large number of mutants, we developed a simple microtiter method for primary screening. Using the classical UV-mutation method plus selection pressures, the production capacity was increased about 0.5 approximately 2.5 times the starting strain. The mutants with higher production and different phenotypes were further subjected to recursive protoplast fusions and the fusants products were screened under multi-selection pressure. Furthermore, the production was greatly increased by the genome shuffling. For epothilone B, the production of one fusant was increased about 130 times compared to the starting strain, increasing from 0.8 mg l(-1) to 104 mg l(-1).