Food-Grade Expression and Characterization of a Dextranase from Chaetomium gracile Suitable for Sugarcane Juice Clarification

The microbial production of dextranase using cheap carbon sources is beneficial to solve the economic loss caused by the accumulation of dextran in syrup. A food-grade microbial cell factory was constructed by introducing the dextranase encoding gene DEX from Chaetomium gracile to the chromosome of Bacillus subtilis, and the antibiotic resistance marker gene was subsequently deleted via the Cre/loxP strategy. The dual-promoter system with a sequentially arranged constitutive P43 promoter resulted in an 85 % increase in DEX expression. Under the optimal fermentation conditions of 10 g/L maltose, 15 g/L casein, 1 g/L Na₂HPO₄, 1 g/L FeSO₄ and 8 g/L NaCl, DEX activity was increased from 2.625 to 64.34 U/mL. Recombinant DEX was purified 5.98-fold with a recovery ratio of 26.67 % and specific activity of 3935.02 U/mg. Enzyme activity was optimal at 55 °C and pH 5.0 and remained 80.34 % and 71.36 % of the initial activity at 55 °C and pH 4.0 after 60 min, respectively. The enzyme possessed high activity in the presence of Co²⁺, while Ag⁺ showed the strongest inhibition ability. The optimal substrate was 20 g/L dextran T-2000. The findings could facilitate the low-cost, large-scale production of food-grade DEX for use in the sugar industry.     

Northern bobwhite response to Conservation Reserve Program habitat and landscape attributes

The northern bobwhite (Colinus virginianus; hereafter bobwhite) has experienced substantial population declines in recent decades in the United States, and especially in Maryland and Delaware. The United States Department of Agriculture's Conservation Reserve Program (CRP) could provide additional habitat for bobwhites, leading to an increase in bobwhite abundance. I investigated if bobwhite abundance was related to the percent cover of CRP land and landscape attributes in local landscapes on Maryland's Eastern Shore and Delaware. Observers conducted bobwhite point transect surveys at 113 locations during the breeding seasons of 2006–2007, and I calculated landscape metrics for 500-m radius landscapes centered on each point transect location. Most CRP land in the study landscapes was planted to herbaceous vegetation. Bobwhite abundance was strongly positively associated with percent cover of CRP land in the landscape but was not strongly related to percent cover of agriculture or forest or to landscape patch density. These results suggest that the CRP has created additional habitat for bobwhites in Maryland and Delaware and that landscapes with greater proportions of herbaceous CRP practices support more bobwhites. © 2012 The Wildlife Society.     

Complex behaviour in four species food-web model

A four-dimensional food-web system consisting of a bottom prey, two middle predators and a generalist predator has been developed with modified functional response. The system is well posed and dissipative. Some results on uniform persistence have been developed. The dynamics of the system is found to be chaotic for certain choice of parameters. The coexistence of all four species is possible in the form of periodic orbits/strange attractors for suitably chosen set of parameters.     

Late emergence chronotypes of fruit flies Drosophila melanogaster exhibit higher accuracy of entrainment

Inter-individual variation in phase-of-entrainment (chronotype) is widely observed in many species, but the underlying mechanisms and its consequences remain largely unexplored. In light of considerable limitations of previous studies proposing that the late chronotypes exhibit weakly stable rhythms, we employed outbred Drosophila populations exhibiting early and late emergence chronotypes to re-visit such associations. Contrary to previous reports, we observed that the late chronotypes consistently exhibit higher stability in emergence and activity–rest rhythms as compared to the early chronotypes, both under laboratory and semi-natural conditions, which is not associated with higher precision of circadian clocks, thus demonstrating the existence of genetic correlations between accuracy of entrainment and chronotype. Our results, along with the previously reported clock property differences between the early and the late emergence chronotypes highlights a possible complex interplay of clock period, phase response curve and accuracy in determining phase-of-entrainment.     

一个具暂时免疫且总人数可变的传染病动力学模型

建立了一个具常恢复率和接触率依赖于总人数的SIRS传染病动力学模型，讨论了系统平衡点的存在性和稳定性，对双线性传染率的特殊情形，给出了传染病平衡点的全局稳定性结论，推广和改进了已有的相应结果。     

Identification of two metabolites induced by a butyrolactone autoregulator IM-2 in Streptomyces sp. FRI-5

Abstract In order to determine whether non-elastase-producing strains of Pseudomonas aeruginosa such as N-10, PA103 and IFO3080 can express foreign elastase genes, we introduced elastase genes from P. aeruginosa IFO3455 (elastase-producing) as well as from PA103 and N-10 into non-elastase-producing P. aeruginosa strains. Results suggested that gene expression, secretion, and precursor processing systems of elastase were essentially normal in P. aeruginosa N-10 and IFO3080. Our studies using various elastase genes showed that both the elastase structural gene and 5'-upstream regions of P. aeruginosa PA103 were also normal. This was confirmed by the finding that P. aeruginosa N-10 and IFO3080 which carry the PA103 elastase gene produced elastase. Several deleted or chimeric genes were constructed using the 5'-upstream regions of elastase genes from P. aeruginosa N-10 or PA103 and studies of expression revealed that two individual DNA bases seem to be important in suppressing P. aeruginosa N-10 elastase gene expression. Possible reasons for the lack of elastase in these non-elastase-producing strains are discussed.     

Chemical synthesis and cloning of a poly(arginine)-coding gene fragment designed to aid polypeptide purification

A 43-bp DNA duplex coding for poly(arginine) [poly(arg)] has been synthesised by modified phosphotriester procedures. It has been inserted into the BglII and BamHI restriction sites of a cloned synthetic β-urogastrone (Uro) gene, under the control of the trp promoter. Subsequent induction with 3β-indole acrylic acid produces β-Uro with a C-terminal poly(arg) fusion. The raised isoelectric point of this polypeptide fusion facilitates rapid purification by cation exchange chromatography. The C-terminal poly(arg) tail can be readily removed by treatment with carboxypeptidase B.     

Structure of the Human TELO2-TTI1-TTI2 Complex

Phosphatidylinositol 3-kinase-related protein kinases (PIKKs) play critical roles in various metabolic pathways related to cell proliferation and survival. The TELO2-TTI1-TTI2 (TTT) complex has been proposed to recognize newly synthesized PIKKs and to deliver them to the R2TP complex (RUVBL1-RUVBL2-RPAP3-PIH1D1) and the heat shock protein 90 chaperone, thereby supporting their folding and assembly. Here, we determined the cryo-EM structure of the TTT complex at an average resolution of 4.2 Å. We describe the full-length structures of TTI1 and TELO2, and a partial structure of TTI2. All three proteins form elongated helical repeat structures. TTI1 provides a platform on which TELO2 and TTI2 bind to its central region and C-terminal end, respectively. The TELO2 C-terminal domain (CTD) is required for the interaction with TTI1 and recruitment of Ataxia-telangiectasia mutated (ATM). The N- and C-terminal segments of TTI1 recognize the FRAP-ATM-TRRAP (FAT) domain and the N-terminal HEAT repeats of ATM, respectively. The TELO2 CTD and TTI1 N- and C-terminal segments are required for cell survival in response to ionizing radiation.