Bacteria Spectra Obtained by Laser Induced Fluorescence

Laser-induced fluorescence technique (LIF) is described for getting bacteria spectra in the liquid phase. An excimer laser pumping a dye-laser and a doubly frequency laser have been used, exciting the bacteria to 290 nm, and using a monochromator, 600 lines/mm grating, with a CCD to measure and obtain the fluorescence spectra. In this study, a laser induced fluorescence system to measure certain bioaerosols (bacteria) was optimised. Finally, a small bacteria fluorescence spectra collection is presented.     

Selection and analytical applications of aptamers binding microbial pathogens

DNA aptamers specifically recognizing microbial cells and viruses have a range of analytical and therapeutic applications. This article describes recent advances in the development of aptamers targeting specific pathogens (e.g., live bacteria, whole viral particles, and virally-infected mammalian cells). Specific aptamers against pathogens have been used as affinity reagents to develop sandwich assays, to label and to image cells, to bind with cells for flow-cytometry analysis, and to act as probes for development of whole-cell biosensors. Future applications of aptamers to pathogens will benefit from recent advances in improved selection and new aptamers containing modified nucleotides, particularly slow off-rate modified aptamers (SOMAmers).     

HPLC Fingerprint Characteristics of Active Materials of Garlic and Other Allium Species

The bioactive molecules of garlic are classified according to their enzymatic activities as either alliinase activators or alliinase inactivators. The alliinase activation reaction system is mainly composed of sulfur-containing compounds, whereas the alliinase inactivation system is mainly composed of amino acid-based materials. The purpose of this study was to develop an effective way to digitally express features of complex active compounds of garlic as a basis for quality control. HPLC was used to develop the fingerprints of plants from different Allium species and different geographical regions according to whether the compounds were sulfur containing or based on amino acids. Using the Shannon equation, I values of sulfur-containing compounds from garlic ranged from 3.55 to 3.94, whereas I values of sulfur-containing compounds from other Allium plants, onions, leek, and Welsh onion, ranged from 3.38 to 3.53. The I values of amino acid-based compounds from garlic ranged from 3.67 to 3.91, whereas I values of these compounds from other Allium plants ranged from 3.88 to 3.99. This method effectively distinguished garlic from different species of Allium plants. This method also provided a way to digitally monitor the presence of complex active compounds of garlic and may allow evaluation of quality. This method may also provide a theoretical basis for quality control of bioactive compounds from other medicinal plants.     

Electropermeabilization responses in Gram-positive and Gram-negative bacteria

Effects of 3-kJ kg^?1 nanosecond pulsed electric fields (PEFs) on cellular permeabilization of Salmonella enterica and Staphylococcus aureus were observed. It was seen that bacterial responses depend on both the electrical pulse attribute and the cell plasma membrane structure. For traditional permeabilization, the responses involved the thickness of the peptidoglycan layer where a maximum of 2.5 log reduction in S. enterica population was achieved. Meanwhile, in the area of selective permeabilization, it showed insignificant reduction in both pathogens. Such inactivation mechanisms were described through the behavior of potential across plasma membrane and intracellular organelles by PSPICE simulations incorporating PEF-cell interaction model.     

Effect of pH and high pressure at sub-zero temperature on the viability of some bacteria

The objective of this study was to investigate the viability of Escherichia coli and Staphylococcus aureus in apple juice after treatment with high pressure at sub-zero temperature and during subsequent storage at 5 and 20 °C. The viability of E. coli and S. aureus cells suspended in the apple juice with a pH of 3.8 did not decrease considerably after pressure treatment at 193 MPa and?20 °C. However, viability losses occurred during storage of samples after pressure treatment. Living cells of both strains were not detected in pressurized samples of apple juice stored for 10 days at 20°C. The lethal effect was lower when the samples after pressure treatment were incubated at refrigerated temperature; the number of E. coli and S. aureus decreased by 6 log cycles when the juice was stored for 10 days at 5 °C.     

温压协同处理黑莓β-葡萄糖苷酶失活动力学研究

 以黑莓β-葡萄糖苷酶为对象,研究其温压协同条件下的失活动力学规律,可为超高压食品处理技术的工业化和花色苷的保留提供有力的技术支持。实验压力为300~600 MPa,温度为35~55 ℃。结果表明：β-葡萄糖苷酶在温压协同条件下的失活过程为两个阶段,第一阶段用瞬时失活值描述,压力和温度影响其大小,不受保压时间影响;第二阶段将β-葡萄糖苷酶分为稳定部分和敏感部分,β-葡萄糖苷酶的失活过程用双相一级反应动力学模型描述,其失活速率常数随温度、压力的升高而增大。敏感部分和稳定部分在400 MPa、55 ℃条件下,失活速率常数K_L和K_S分别为2.777和0.047 min^-1,二者失活90%所需时间D_L和D_S分别为0.83和49.1 min。在400 MPa条件下,敏感部分的D值减少90%所需增加的温度T_Z和活化能E_a分别为23.36 ℃和81.95 kJ/mol;在45 ℃条件下D值减少90%所需增加的压力p_Z和活化体积V_a分别为1 111 MPa和-5.02 cm³/mol。     

50 Hz magnetic field effect on the morphology of bacteria

Atomic force microscopy was used to distinguish changes in morphology of bacteria induced by 50 Hz 10 mT magnetic field exposure. It is known that alternating magnetic field exposure causes decrease of viability of different bacterial strains. Previously we found that the viability of rod-like bacteria exposed to magnetic field decreased twice more in comparison with the spherical ones. Motivated by this fact we carried out this study with bacterial cells of both shapes. We used Escherichia coli (rod-like) and Paracoccus denitrificans (spherical) bacteria. As a result we have not observed any change in bacterial morphology neither of rod-like nor of spherical bacteria after 1 h, 50 Hz and 10 mT magnetic field exposure.     

PCR生物微流体芯片中的表面钝化技术

聚合酶链式反应（polymerase chain reaction,PCR）是一种重要的体外DNA扩增技术,在生物化学、分析化学以及分子生物学等领域中得到广泛的应用．基于微电子机械系统（Microelectromechanical system,MEMS）技术构建而成的PCR生物微流体芯片由于具有反应速度快、样品消耗少以及所占空间体积少等优点而倍受人们亲睐．然而,伴随之较大比表面积以及其所用的裸露衬底材料常常抑制PCR反应,从而导致PCR不能顺利进行．本文结合本试验室的研究工作,综述了PCR生物微流体芯片中为了获得“友善”的PCR扩增体系而采取的表面钝化技术,主要包括表面钝化的必要性、静力学／动力学表面钝化技术以及硅相关材料对PCR抑制的机制等等．