手机辐射对大肠杆菌生长影响作用的研究

目的：探索了解手机辐射对大肠杆菌生长与繁殖的影响。方法：用不同型号的手机以通话方式对大肠杆菌进行辐射,检测大肠杆菌培养后的茵落的大小和数量,比较实验组与对照组的差异。结果：对照组与手机辐射组茵落数量相近,经统计学分析,两组菌落数差别无显著性,但是经手机辐射后,菌落的直径大于对照组,不同型号的手机之间也有差别,且差别有显著性（P〈0．05）。结论：手机辐射对大肠杆菌生长可能有影响,但其具体机制还有待进一步的研究进行阐明。     

Impact of Three Ampicillin Dosage Regimens on Selection of Ampicillin Resistance in Enterobacteriaceae and Excretion of blaTEM Genes in Swine Feces

The aim of this study was to assess the impact of three ampicillin dosage regimens on ampicillin resistance among Enterobacteriaceae recovered from swine feces by use of phenotypic and genotypic approaches. Phenotypically, ampicillin resistance was determined from the percentage of resistant Enterobacteriaceae and MICs of Escherichia coli isolates. The pool of ampicillin resistance genes was also monitored by quantification of bla_TEM genes, which code for the most frequently produced β-lactamases in gram-negative bacteria, using a newly developed real-time PCR assay. Ampicillin was administered intramuscularly and orally to fed or fasted pigs for 7 days at 20 mg/kg of body weight. The average percentage of resistant Enterobacteriaceae before treatment was between 2.5% and 12%, and bla_TEM gene quantities were below 10⁷ copies/g of feces. By days 4 and 7, the percentage of resistant Enterobacteriaceae exceeded 50% in all treated groups, with some highly resistant strains (MIC of >256 μg/ml). In the control group, bla_TEM gene quantities fluctuated between 10⁴ and 10⁶ copies/g of feces, whereas they fluctuated between 10⁶ to 10⁸ and 10⁷ to 10⁹ copies/g of feces for the intramuscular and oral routes, respectively. Whereas phenotypic evaluations did not discriminate among the three ampicillin dosage regimens, bla_TEM gene quantification was able to differentiate between the effects of two routes of ampicillin administration. Our results suggest that fecal bla_TEM gene quantification provides a sensitive tool to evaluate the impact of ampicillin administration on the selection of ampicillin resistance in the digestive microflora and its dissemination in the environment.     

重组大肠杆菌高密度培养研究进展

重组大肠杆菌细胞高密度培养(High cell-density cultivation,HCDC)是获得高外源蛋白产率的一种重要策略,影响重组大肠杆菌高密度培养的因素主要有以下几个方面:重组体的构建及其稳定性,培养基成分,培养方式,培养条件及培养过程中抑制性代谢产物的积累等。从以上几个方面对近期的研究进展进行了综述。     

Accumulation of E. Coli bacteria in mini-channel flow

The objective of this research is to design and optimize a mini/micro-channel based surface-accumulator of E. coli bacteria to be detected by acoustic wave biosensors. A computational approach has been carried out using the state of the art software, CFD-ACE with water as bacteria bearing fluid. E. coli bacteria have been modeled as random discrete particles tracked by solving the Lagrangian equations. The design challenges are to achieve low shear force (pico-N), high concentration at accumulation, and high enough Reynolds number to avoid bacteria swimming. A range of low Reynolds number (Re) has been considered along with the effects of particle boundary interactions, gravity, Saffman lift, etc. More than two orders of magnitude higher concentration at the accumulation than the inlet concentration, and lower shear force of less than pico-N have been achieved in the optimized designs.     

低能氮离子注入大肠杆菌诱发的生物学效应研究

研究离子注入的诱变和导入外源DNA的生物学效应,用低能氮离子注入处理大肠杆菌野生型菌株MC4100A,将含水母绿色荧光蛋白基因的质粒导入细胞中。实验结果表明,在一些转化子中绿色荧光蛋白的表达或折叠受到了影响,一些转化子丧失了分裂后分离能力,且细胞膜有一定程度的损伤,为进一步研究微生物细胞分裂和蛋白质折叠机理提供了菌株。故低能氮离子注入对微生物细胞的诱变效应和导入外源DNA效应的有机结合将使离子注入技术在生物学基础研究中有着广泛的应用前景。     

Biosynthesis of polyribonucleotide phosphorylase and polyribonucleotides by E. Coli

The biochemical functions of Polyribonucleotide phosphorylase (PNP-ase; EC 2.7.7.8) has been studied The present work was aimed at studying the interrelation between PNP-ase biosynthesis and RNA content of E. coli cells under various conditions of bacterial growth, obtaining the biomass of E. coli with high PNP-ase activity as well as to study the possibility of secondary cultivation of E. coli cells for obtaining polyribonucleotides from nucleoside-5′-diphosphates The spcific PNP-ase activity increases at secondary cultivation, when the medium contains ribonucleoside-5′-diphosphates. Besides one may observe an extracellular polycondensation of nucleoside-5′-diphosphates It may be presumed that the PNP-ase is a multifunctional enzyme whose biological role may be confined to regulating the energetic processes connected with the metabolism of glucose, nucleosidephosphates and orthophosphate in the cells of E. coli.     

Binding of metal ions to apoalkaline phosphatase from E. Coli: Effect of ionic radius

Binding of metal ions to $\text{E. Coli}$ apoalkaline phosphatase causes 1) chromophoric changes in tyrosine absorption, 2) changes in enzymatic activity and 3) the release of protons from the enzyme. Investigation of these effects for a selection of metal ions from the Group 11A, Group 11B and transition series revealed that only those ions having crystal ionic radii in the range of 0.72 – 0.99A are able to produce changes in these three properties. The hydrated ionic radii, which are in the range of 4.0 – 4.5A for the ions examined do not correlate well with the ability of the ion to affect the three properties studied here. The size requirement therefore would seem not to apply to the initial binding step which undoubtedly involves the hydrated ion. Rather, the size requirement reflects the size range of a binding site generated by the folding of the protein around the metal ion with concomitant displacement of water molecules from the coordination sphere of the metal.     

重组人内皮抑素工程菌菌种稳定性考察

研究重组人内皮抑素突变体质粒HM-E的宿主菌E．coliBL21（DE3）在LB培养基中传代50代过程中菌种的稳定性。研究表明,重组人内皮抑素工程菌在传代50代的过程中质粒稳定性（ST）高,为98％,菌体与菌落呈典型的大肠杆菌形态,反复冻融后表达量未下降,目标蛋白在菌体超声的沉淀中质量分数为（58．75±3．78）％,同时,四甲基偶氮唑盐微量反应比色法（MTT）结果表明目的蛋白质量浓度为20μg／mL时对内皮细胞ECV-304具有很高的抑制率,达（94．72±2．10）％。     

The Molecular Genetics of Superoxide Dismutase in E. Coli

The biological role and the regulation of superoxide dismutase (SOD) in E. coli have been investigated using genetics. Cloning of both E. coli SOD genes permitted construction of mutants completely lacking SOD. The conditional oxygen sensitivity of those mutants, together with their increased mutation rate, demonstrated the essential biological role of SOD. SOD-deficient mutants constitute a powerful tool to assess a possible role of O^?2 or SOD in biological processes. Complementation of their deficiencies by the expression of SOD originating from a different organism is used for screening libraries for SOD genes of other species. Regulation of MnSOD has been studied using protein and operon fusions with the lactose operon, and isolating regulation mutants. These studies reveal multiregulation of MnSOD including response to the superoxide mediated oxidative stress and response to variations of the intracellular redox state induced by metabolic changes.     

E. Coli Transfer RNA: Fractionation By Electrophoresis on Polyacrylamide Gel

1. The tRNA (4S) of E. coli has been fractionated by electrophoresis on polyacrylamide gel and separated into two electrophoretic classes designated 4S RNA A and 4S RNA B.     

大肠杆菌中的小分子RNA

迄今为止,已知由大肠杆菌基因组编码的小分子ＲＮＡ（ｓＲＮＡ）除了５ＳｒＲＮＡ和ｔＲ－ＮＡ外,共有１０种,其中大多数是调控ＲＮＡ,可调控细菌的某些代谢过程。１．ｓＲＮＡ的发现用聚丙烯酰胺凝胶电泳分析３２Ｐ标记的大肠杆菌总ＲＮＡ,发现除５ＳｒＲＮＡ和ｔＲ...