活细菌作为抗肿瘤药物递送载体的研究进展

细菌可以选择性地在肿瘤部位定殖并抑制肿瘤生长,是递送抗肿瘤药物的良好载体。以活细菌为载体递送抗肿瘤药物的系统具有生物相容性好、靶向性强等特点。然而,细菌自身的免疫原性限制了其作为药物递送载体的发展。本文从底盘细菌的选择、细菌负载药物策略、抗肿瘤药物递送应用及其局限性等方面进行了详细阐述,并展望了其未来的发展方向,为活细菌作为抗肿瘤药物递送载体的研究提供了参考。     

Inhibiting sulfate-reducing bacteria in biofilms by expressing the antimicrobial peptides indolicidin and bactenecin

To identify novel, less-toxic compounds capable of inhibiting sulfate-reducing bacteria (SRB), Desulfovibrio vulgaris and Desulfovibrio gigas in suspension cultures were exposed to several antimicrobial peptides. The bacterial peptide antimicrobials gramicidin S, gramicidin D, and polymyxin B as well as the cationic peptides indolicidin and bactenecin from bovine neutrophils decreased the viability of both SRB by 90% after a 1-h exposure at concentrations of 25–100 μg ml⁻¹. To reduce corrosion by inhibiting SRB in biofilms, the genes for indolicidin and bactenecin were expressed in Bacillus subtilisBE1500 and B. subtilis WB600 under the control of the constitutive alkaline protease (apr) promoter, and the antimicrobials were secreted into the culture medium using the apr signal sequence. Bactenecin was also synthesized and expressed as a fusion to the pro-region of barnase from Bacillus amyloliquefaciens. Concentrated culture supernatants of B. subtilis BE1500 expressing bactenecin at 3 μg ml⁻¹ decreased the viability of Escherichia coli BK6 by 90% and the reference SRB D. vulgaris by 83% in suspension cultures. B. subtilis BE1500 and B. subtilis WB600 expressing bactenecin in biofilms also inhibited the SRB-induced corrosion of 304 stainless steel six to 12-fold in continuous reactors as evidenced by the lack of change in the impedance spectra (resistance polarization) upon addition of SRB and by the reduction in hydrogen sulfide and iron sulfide in batch fermentations with mild steel. A 36-fold decrease in the population of D. vulgaris in a B. subtilis BE1500 biofilm expressing bactenecin was also observed. This is the first report of an antimicrobial produced in a biofilm for in vivo applications and represents the first application of a beneficial, genetically-engineered biofilm for combating corrosion. Received 27 October 1998/ Accepted in revised form 21 February 1999     

Microbial diversity in soil: effect of releasing genetically engineered micro-organisms

This review examines the potential for change in microbial diversity, with the emphasis on bacteria, in soil resulting from the introduction of genetically engineered microorganisms (GEMs). With the advent of GEMs came the impetus for new technologies to recover these micro-organisms from soil and to assess their effects on microbial diversity. This review also presents general aspects of and genetic approaches to accessing bacterial diversity in the environment.     

基因工程菌生产抗菌肽的研究进展

目前,利用基因工程菌生产抗菌肽,提供有效和稳定的方法是抗菌肽生产的热点之一。了解抗菌肽工程菌表达系统、生产量尤为重要,为此本文阐述了抗菌肽的生产方式,介绍了基因工程菌表达系统的种类、组成及特点,分析了基因工程菌生产抗菌肽的主要困难因素,并对近些年利用基因工程菌生产抗菌肽的进展进行了综述。     

棉花抗虫工程菌对棉铃虫的离体及活体生物测定

棉花抗虫工程菌是以能在棉株体内定殖的优势内生细菌Bacillus cereus (Bc9102)为宿主菌,将Bt kurstaki的δ-内毒素基因cryIA©整合到其染色体上形成的内生工程菌。以棉铃虫Helicoverpa armigera为供试昆虫的离体生测结果表明：在同一剂量水平上,HE-1、HE-2、ME14-2、ME14-3、MK14-1等工程菌株对棉铃虫幼虫的毒力高于或等于Bt野生菌株HD-73,浓度最高时这几个工程菌处理的棉铃虫死亡率分别为96.7%、83.3%、93.3%、83.3%、80.0%,而HD-73为80.0%,死亡率与浓度呈正相关。在用上述工程菌接种棉花的活体生测中,注射处理和喷雾处理法杀虫效果均优于浸种处理法。以HE-1为例,注射、喷雾、浸种处理4周后棉铃虫校正死亡率分别达到90.0%、76.0%和23.3%。工程菌对棉铃虫的生长发育也有抑制作用。     

基因工程技术在降解农药中的应用

综述了基因重组、原生质体融合、外源基因、降解酶和固相反应器等基因工程技术在降解农药中的研究及应用进展,提出了几种高效降解农药的基因工程菌的构建策略和构建手段。     

天蚕素AD在毕赤酵母中的多拷贝整合表达及表达条件优化

【背景】天蚕素抗菌肽是目前研究最清楚、效果最显著的抗菌肽,实现工业化生产为其在农业、养殖业中的应用奠定了基础。【目的】获得一株高效生产天蚕素AD的基因工程菌株。【方法】构建重组载体pGAPZαA-CAD通过电击转化至PichiapastorisX33中,表达天蚕素AD基因并获得X33/GCAD菌株;构建重组载体pUCGAP-CAD导入至X33/GCAD菌株中。pGAPZαA-CAD是以博来霉素为抗性筛选标签被整合到P. pastoris X33的GAPDH启动子区域,pUCGAP-CAD是以遗传霉素为抗性筛选标签被整合到P. pastoris X33的非翻译rDNA区域,最终获得一株高效表达天蚕素AD的酵母菌株X33/GUCAD。【结果】通过质谱分析鉴定X33/GUCAD表达的抑菌物质为天蚕素AD,通过发酵条件的优化,表明X33/GUCAD菌株在以甘油为碳源和以蛋白胨、酵母提取物为有机氮源的情况下具有较强表达天蚕素AD的能力。【结论】较高的拷贝数更有利于提高天蚕素AD的产量,此工程菌株在后期发酵过程中稳定性较好,适于工业化生产。     

The influence of moisture on microbial transport, survival and 2,4-D biodegradation with a genetically marked Burkholderia cepacia in unsaturated soil columns

The influence of moisture on the survival, movement anddegradation activity of a 2,4-D degrading bacterium,Burkholderia cepacia strain BRI6001L, geneticallyengineered to contain bioluminescent and lactoseutilization genes, was studied in unsaturated soil columns.The distance traveled by BRI6001L was dependent on theclay content of the soil, higher clay contents beingresponsible for higher filtration coefficients. Long termsurvival, in excess of one year, was attributed to strainBRI6001L's ability to survive dry conditions. Changes inthe 2,4-D biodegradation rate showed a better correlationwith the BRI6001L population density than with the totalviable bacterial population. At moisture levels betweenfield capacity and 40% moisture (– 33 kPa to –100 kPa)2,4-D degradation was attributed mainly to BRI6001L. Atmoisture levels between 6 and 15%, 2,4-D disappearancewas attributed to the indigenous microbial population,with no degradation occurring at moisture levels below6%. Returning the moisture to above 40% led to anincrease of 4 orders of magnitude in the BRI6001Lpopulation density and to a 10-fold increase in the 2,4-Ddegradation rate. The ability to monitor a specificmicrobial population using reporter genes hasdemonstrated the importance of controlling moisturelevels for maximizing biodegradation rates in unsaturatedsoil environments.     

改造肠道微生物在疾病诊断与治疗中的应用

肠道微生物是近年来新兴的热门研究领域,它与人类疾病健康存在着密切的关系。伴随高通量测序技术的发展,研究者们发现了肠道微生物在疾病的诊断与治疗中的潜力。合成生物学通过设计编辑工具以及反馈回路,可以构建具有诊断疾病或者靶向治疗疾病的肠道微生物工程菌株。这些工程菌能够对环境进行感知、计算和反馈。本文概述了改造后的肠道微生物在疾病诊断与治疗中的应用,同时阐述了目前改造后肠道微生物的临床应用现状,并对\"工具短缺\"以及目前改造后肠道微生物所存在的安全性等问题进行了讨论。     

玉米内生杀虫工程菌对玉米螟的离体及活体生物测定

12#Bt/CXC是以能定植在玉米维管束系统的内生菌I>Clavibacter xyli subsp.Cynodon—tis(CXC)为宿主菌,将Bt urstaki的δ—内毒素基因cryIA?整合到其染色体上形成的内生工程菌。以玉米螟Ostrinia furnacalis Guenee为供试昆虫的生测结果表明：在同一浓度下,12^#菌株对玉米螟的毒力均高于野生型Bt菌株HD73和空白对照(最低浓度除外)。浓度最高时12^#处理的死亡率为63%,而m工73为53%,死亡率与浓度呈正相关,相关系数r₁₂^#大于r_HD—73。在用12^#Bt/CXC接种玉米的活体生测中,人工接虫4周后检测,注射接种法效果明显优于种子处理法。不同浓度的注射接种处理,玉米螟幼虫减少率最低70%,最高可达96%,与未处理对照相比差异显著。12#菌剂处理后对玉米螟的生长发育也有抑制作用,虫体重减轻26.4%～44.5%,处理株虫龄平均为2龄,而对照株为4龄。     

产姜黄素大肠杆菌工程菌的构建

姜黄素是姜科植物的特征性成分,具有重要的药理活性.文中利用姜黄素生物合成关键酶β-酮酰辅酶A合酶(Diketide-CoA synthase,DCS)基因和姜黄素合酶(Curcumin synthase,CURS)基因构建非天然融合基因DCS::CURS,并将其与4-香豆酰辅酶A连接酶(4-coumarate coen...     

基于相邻木排列关系的混交度研究

混交度是反映森林群落中树种相互隔离状况的一个重要指标,目前已提出多种混交度指数.Mg考虑了对象木与最近相邻木的树种异同,Mv和Ms进一步考虑了最近相邻木(空间结构单元)树种数,但仍不能准确描述树种隔离程度.基于相邻木排列关系的混交度Mp,利用“1+4”结构的17个不同空间结构单元和天目山常绿阔叶林数据对Mg、Mv、Ms和Mp4个混交度进行了比较分析.结果表明:Mp的区分能力最强,Mv和Ms次之,Mg最差.Mp最适用于分析混交结构复杂的林分.在天目山常绿阔叶林分析中,混交度水平为中度,4个最近邻体中有2个相同种顺序排列的空间结构单元个数明显多于交错排列的个数.基于相邻木排列关系的混交度Mp能准确区分树种隔离程度,提高了混交度的区分度,可反映森林实际混交状况.     

联合固氮的研究进展

1975年,Dbereiner实验发现与禾本科植物联合共生的固氮菌并提出根际联合固氮的概念。近年来,随着一些新的研究手段包括化学分析、遗传工程、分子生物学、免疫学等方法的运用,推进了联合固氮领域的研究深度。综述了近年来发现的联合固氮菌的种类;联合固氮体系的形成过程（趋化、结合和侵入）;影响联合固氮的主要因素：自然条件、土著微生物的竞争、植物基因型差异和环境条件的变化、结合态氮（氨、亚硝酸盐、硝酸盐等）和氧。并从固氮联合作用测定方法、联合固氮菌的资源筛选、联合固氮工程菌的研究、联合固氮分子生态学研究方法4个方面,论述了联合固氮的研究现状。     

On interacting populations that disperse to avoid crowding: The effect of a sedentary colony

An analysis is given of a model for two interacting species, one mobile and the other sedentary, in which the mobile one disperses to avoid crowding. The spatial distribution of the mobile species over the habitat, as it evolves with time, is studied. In particular it is shown that a colony of the sedentary species can form an effective barrier against the spreading mobile species, and prevent it from entering certain parts of the habitat.