Subjects: Biology >> Zoology submitted time 2017-10-23 Cooperative journals: 《动物营养学报》
Abstract：随着养猪业集约化、工厂化的发展，为了方便管理和降低成本，实际生产中常常扩大饲养密度，导致猪生存空间和食物等不足，诱发猪心理和行为方式等的改变。此外，高饲养密度加大了猪舍内环境负担，使舍内有害气体含量增多，增加了呼吸道和消化道疾病发生的概率，严重影响着猪群的健康并制约猪生长性能的发挥。本文就饲养密度对猪群健康和猪舍环境的影响做一论述。
Subjects: Biology >> Zoology submitted time 2017-10-10 Cooperative journals: 《动物营养学报》
Abstract：色氨酸是一种具有调节机体免疫功能的必需氨基酸。色氨酸的代谢产物吲哚-2,3-双加氧酶（IDO)、犬尿氨酸、喹啉酸和褪黑激素等，可通过抑制T淋巴细胞增殖、增加血液免疫球蛋白含量和促进组织的抗原递呈等，来提高机体免疫力、抗炎症反应和影响肿瘤细胞免疫逃逸。本文就色氨酸及其代谢产物对畜禽免疫功能的调控作用和机制进行简要叙述。
Subjects: Biology >> Bioengineering submitted time 2017-07-24 Cooperative journals: 《中国生物工程杂志》
Abstract： Objective: This study focuses on the influence of overexpression of β-glucosidase regulator BglR on beta-glucosidase activities in Myceliophthora thermophila ATCC42464 by cloning bglr gene and constructing Mtbglr overexpression vector. Methods: The SLIC was adopted to construct Mtbglr overexpression vector and the promoter of MtPpdc and terminator of MtTpdc was used for overexpress bglr gene. The gene expression and β-glucosidase activities were observed by protoplast transformation, real-time quantitative PCR and enzymatic determination. Results: The bglr gene was overexpressed in M. thermophila successfully. The result showed that the β-glucosidase activity and secreted protein concentration of transformant strain Mt8 were 1.7 and 1.9 fold higher, respectively, than that of wild type WT. Conclusion: The expression of bglr increased the β-glucosidase activity in Myceliophthora thermophila under the inducing condition, which laid the theoretical foundation for the regulation of β-glucosidase gene of thermophilic fungi.
Subjects: Biology >> Bioengineering submitted time 2017-07-24 Cooperative journals: 《中国生物工程杂志》
Abstract： Objective: The XylR-Pu is a classic toluene catabolic pathway, which is from TOL plasmid of Pseudomonas putida. In the presence of toluene, the XylR regulatory protein can activate Pu promoter and thus induce expression of corresponding metabolic genes. To detect 2,4,6-trinitrotoluene (TNT),the significant environmental pollutant, the pathway was optimized and put into Escherichia coli to construct whole-cell biosensor, which was based on the idea of synthetic biology. E.coli was chosen as chassis cell due to its genetic background was clear and it was simple to operate. Methods: pETDuet-1 was used as backbone to construct gene circuit of XylR-Pu, XylR was inserted in first multi cloning site . The second T7 promoter was substituted by Pu promoter and reporter gene of green fluorescent protein was under the control of Pu promoter . The fluorescent values can indicate the strength of the activation of XylR protein to Pu promoter. Then four series terminator was inserted between XylR and Pu to minimize background expression. Finally, the receptor domain of XylR protein was randomly mutated using sequential error prone PCR to construct a mutant library and to identify XylR mutants, which can be more sensitive and specific to TNT. Results: The four series terminator can effectively prevent read-through and decrease background fluorescent. After selection, one mutant protein named eX0-4 displayed better induction intensity, sensitivity and specificity to TNT. Conclusions: As Nitrobenzene was not XylR natural inducer, so XylR showed no obvious response to TNT. But the method is feasible to modify the A domain of XylR protein to obtain non-natural but better protein components. The mutant of eX0-4 enriched the reservoir of TNT-sensing elements, and provided a more applicable toolkit to be applied in genetic routes and live systems of biosensors in future. It can be a common method to identify biological elements to use error prone PCR to construct mutant library.
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