Parasitism ofAphis gossypii (Homoptera: Aphididae) byAllothrombium pulvinum larvae (Acari: Trombidiidae) in cotton fields: spatial dispersion and density dependence

Spatial aspects of the interaction between the aphid host,Aphis gossypii, and its parasite,Allo-thrombium pulvinum larvae, on cotton plants were examined in seven fields in China. For both the host and the parasite, sample variance increased with the mean according to Taylor's power law, which explained a substantial proportion (84–97%) of the variation in the data. Although both the host and parasite showed aggregated distribution on cotton plants, the host aphids aggregated more strongly than the parasites. The host dispersion pattern was not significantly affected by the presence of parasites. Increasing the spatial scales of observation from individual plot to the entire field also had no significant effects on host and parasite dispersion patterns. Parasites aggregated in cotton plants with higher aphid densities in five out of the seventeen samples. Spatial patterns of parasitism were mostly host density-independent (71% of the samples) and sometimes inversely density-dependent (29% of the sample). The processes underlying these patterns were discussed.     

Enhanced catalytic efficiency and enantioselectivity of epoxide hydrolase from Agrobacterium radiobacter AD1 by iterative saturation mutagenesis for (R)-epichlorohydrin synthesis

Applied Microbiology and Biotechnology - Enantioselective hydrolysis of epoxides by epoxide hydrolase (EH) is one of the most attractive approaches for the synthesis of chiral epoxides. So far,...     

Isolation of enantioselective α-hydroxyacid dehydrogenases based on a high-throughput screening method

To isolate enantioselective α-hydroxyacid dehydrogenases (α-HADHs), a high-throughput screening method was established. 2,4-Dinitrophenylhydrazine solution forms a red-brown complex with ketoacid produced during the α-HADH-mediated oxidation of α-hydroxyacid. The complex can be easily quantified by spectrophotometric measurement at 458?nm. The enantioselectivity of α-HADH in each strain can be measured with this colorimetric method using (R)- and (S)-α-hydroxyacid concurrently as substrates to evaluate the apparent enantioselectivity (E _app). The E _app closely matches the value of true enantioselectivity (E _true) determined by HPLC analysis. With this method, a total of 34 stains harboring enantioselective α-HADHs were selected from 526 potential α-HADH-producing microorganisms. Pseudomonas aeruginosa displayed the highest (S)-enantioselective α-HADH activity. This strain appears promising for potential application in industry to produce (R)-α-hydroxyacids. The method described herein represents a useful tool for the high-throughput isolation of enantioselective α-HADHs.     

鼠疫疫苗研究的现状与展望

鼠疫（Plague）是由鼠疫耶尔森菌(Yersina pestis，Y. pestis)（简称鼠疫菌）引起的一种烈性传染病，属甲类传染病，具有高度传染性和致病性。在过去的鼠疫大流行中近2亿感染者死亡。疫苗接种是疾病预防控制的重要方法。现就鼠疫疫苗的研究进展作一综述，为新疫苗的研制提供参考。