肠道微生物与疾病关系的研究新进展- 运用454 测序技术分析

由于传统研究方法成本和速度的限制,远远满足不了对微生物群落大规模的研究,以454测序为代表的新一代高通量测序技术凭借低成本、高通量、流动自动化的优势为研究微生物的多样性和组成提供了新的技术平台。本文就近年来454测序技术在研究人体肠道微生物与疾病关系的应用进行了综述。     

表面活性剂调控瘤胃营养功能研究进展

表面活性剂分为化学表面活性剂和生物表面活性剂两大类,非离子表面活性剂和生物表面活性剂作为新型反刍动物饲料添加剂,可通过改变瘤胃液乳化特性、瘤胃微生物种群数量、分泌酶活性、酶吸附能力和瘤胃发酵模式,来增强瘤胃微生物对粗饲料的降解能力,进而提高反刍动物生产性能。综述提出了表面活性剂在反刍动物瘤胃营养调控领域的研究重点。     

Expression of serotonin derivative synthetic genes on a single self-processing polypeptide and the production of serotonin derivatives in microbes

Soils are rich in organics, particularly those that support growth of plants. These organics are possible sources of sustainable energy, and a microbial fuel cell (MFC) system can potentially be used for this purpose. Here, we report the application of an MFC system to electricity generation in a rice paddy field. In our system, graphite felt electrodes were used; an anode was set in the rice rhizosphere, and a cathode was in the flooded water above the rhizosphere. It was observed that electricity generation (as high as 6 mW/m², normalized to the anode projection area) was sunlight dependent and exhibited circadian oscillation. Artificial shading of rice plants in the daytime inhibited the electricity generation. In the rhizosphere, rice roots penetrated the anode graphite felt where specific bacterial populations occurred. Supplementation to the anode region with acetate (one of the major root-exhausted organic compounds) enhanced the electricity generation in the dark. These results suggest that the paddy-field electricity-generation system was an ecological solar cell in which the plant photosynthesis was coupled to the microbial conversion of organics to electricity.     

Volatile Organic Compounds and Their Roles in Bacteriostasis in Five Conifer Species

In order to make clear the functions of plant volatile organic compounds (VOCs) on bacteriostasis and air decontamination, we analyzed the composition and content of VOCs in Pinus tabulaeformis Carr., P. bungeana Zucc., Sabina chinensis Antoine, Picea koraiensis Nakai, and Cedrus deodara G. Don under near-natural conditions using the thermal-desorption cold trap gas chromatography/mass spectrometer technique. The effects of the VOCs on airborne microorganisms were investigated using the method of natural sedimentation. Results showed that the major VOCs were as follows: limonene, β-pinene, α-pinene,and α-caryophyllene in Pinus tabulaeformis and P. bungeana; limonene, borneol acetate, β-pinene, myrcene, and tricylene in S. chinensis; limonene, α-pinene, myrcene, camphene, and β-pinene in Picea koraiensis; and limonene, 2, (10)-pinene, α-pinene, and myrcene in C. deodara. These VOCs and the corresponding foliar extracts inhibited the growth of bacteria and stimulated the growth of fungi. Experimental data using monomers of the VOCs demonstrated that limonene, β-pinene, and three aldehydes could significantly inhibit bacterial growth, suggesting an inhibitory effect of VOCs on the growth of airborne microorganisms in the five conifer species. The bacteriostasis and air-decontaminating effects of plant VOCs are further discussed in terms of their chemical composition.     

白曲霉工程菌TR12循环转化酒精废液研究

在含固体残渣8％的酒精废液中,加入尿素2g／L、玉米浆2mL／L,经接种白曲霉基因工程菌TRl2菌株,在32℃摇床培养70h后,可获得含糖化酶246U／mL和耐酸性α-淀粉酶13．42U／mL的转化液。转化液直接循环利用于无蒸煮酒精发酵配料工序,不仅不影响酒精生产的产量和质量,而且能有效地减轻环境污染压力,节约水资源,降低生产成本。     

落叶松根际土壤磷的有效性研究

野外用剥落法采集落叶松(Larixgmelini)根际土与非根际土,分析P浓度的变化,结果表明,落叶松根际土与非根际土全P浓度无明显差异,但根际土有效P却明显高于非根际土.12年生时根际土有效P增加12.6%,40年生时增加23.4%,表明落叶松根际对土壤中的P具有活化作用.落叶松根际土无机P各组分与非根际土亦有差异,表现出根际土OP低于非根际土,AlP、FeP、CaP和NH4ClP则高于非根际土的趋势.落叶松根际土的pH低于非根际土,但落叶松根际并未发生明显酸化.落叶松根际有效P与pH变化相关不显著.     

Rhizobium tropiciteu genes involved in specific uptake of Phaseolus vulgaris bean-exudate compounds

Rhizobium tropici nodulates and fixes nitrogen in bean. In the R. tropici strain CFN299 we identified and characterized teu genes (tropiciexudate uptake) induced by bean root exudates, localized by insertion of a promoter-less Tn5-gusA1 transposon. teu genes are present on a plasmid of around 185 kb that is conserved in all R. tropici strains. Proteins encoded by teu genes show similarity to ABC transporters, specifically to ribose transport proteins. No induction of the teu genes was obtained by treatment with root exudates from any of several other plants tested, with the exception of Macroptilium atropurpureum, which is also a host plant for R. tropici. It appears that the inducing compound is characteristic of bean and closely related legumes. It is present in root exudates, but not in seeds. This compound is removed, presumably by metabolism, from the exudates by the majority of bean-nodulating rhizobia (such as R. etli, R. leguminosarum bv. phaseoli and R.␣giardinii). The principal inducing compound has not been identified, but some induction was obtained using trigonelline. The CFN299 strain seems to have an additional uptake system, as no phenotype is observed in two different mutants. R. tropici strain CIAT899, on the other hand, must have only one uptake system, since a mutant bearing an insertion in the teu genes could not remove the compound from the exudates as efficiently as the wild type, and it showed diminished nodulation competitiveness. Received: 21 November 1997 / Accepted: 18 March 1998