Proteomic analysis of the sarcosine-insoluble outer membrane fraction of Flavobacterium columnare

Outer membrane proteins (OMPs) of bacteria are key molecules interacting with the host environment. Flavobacterium columnare, a pathogen-causing columnaris disease of fish worldwide, was studied in order to understand the composition of its OMPs. The sarcosine-insoluble membrane fraction of the OMPs was analysed using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) in combination with reverse-phase high-performance liquid chromatography-tandem mass spectrometry (RP-HPLC MS/MS). Thirty-six proteins were identified, including proteins involved in cell wall/membrane biogenesis, specific transport of various nutrients and in essential metabolism. The present study is the first report on the OMPs of F. columnare, and may serve as the basis for understanding the pathogenesis of the bacterium.

Effects of ytterbium ion on the growth, metabolism and membrane fluidity of Tetrahymena thermophila

Power-time curves and metabolic properties of Tetrahymena thermophila BF5 exposed to different Yb3+ stop levels were studied by ampoule method of isothermal calorimetry at 28 degrees C. Metabolic rate (r) decreased significantly while peak time (PT) increased with the increase of Yb3+ stop. These results were mainly due to the inhibition of cell growth, which corresponded to the decrease of cell number obtained by cell counting. Compared with cell counting, calorimetry was sensible, easy to use and convenient for monitoring the toxic effects of Yb3+ stop on cells and freshwater ecosystem. It was also found that cell membrane fluidity decreased significantly under the effects of Yb3+ stop, which indicated that Yb3+ could be membrane active molecules with its effect on cell membranes as fundamental aspect of its toxicity.

Optimization of operational conditions in a submerged membrane bioreactor

In this study, optimization of operational conditions of a submerged membrane bioreactor treating municipal waste-water was studied. Mixed liquid suspended solid (MLSS), membrane flux (J(v)), aeration (Q), ratio of pumping, time to break time (t(p)/t(b)), and ratio of up flow area to down flow area (A Ad) were chosen as the easily manipulable parameters to study their effects on removal efficiency and membrane fouling. Totally, 16 different runs were designed to compare and select the best combination of the 5 parameters. The results showed that the optimal operational conditions were MLSS = 7g(.)L(-1), J(v) = 10L(.)m(-2.)h(-1), Q = 6 m(3.)h(-1), t(p)/t(b)= 4 min/1 min, and A(r)/A(d) = 1.7 m(2)/m(2). Under such conditions, the SMBR could achieve a double win of high removal efficiency and low membrane fouling.

Characterization of two membrane-associated protease genes obtained from screening out-membrane protein genes of Flavobacterium columnare G(4)

In order to identify genes encoding the outer membrane proteins (OMPs) of the myxobacter Flavobacterium columnare G(4), the expression library of the bacterium was screened by using rabbit antisera developed against its OMPs. Positive colonies of Escherichia coli M15 containing fragments encoding the bacterial OMPs were selected for cloning the relevant genes by genomic walking methods. Two genes encoding a membrane-associated zinc metalloprotease and prolyl oligopeptidase are reported in this paper. The membrane-associated zinc metalloprotease gene (map) is 1800 bp in length, coding for 449 amino acids (aa). Despite the presence of a conserved motif HEXXH for all metalloproteases, the special HEXXH similar to 32 aa similar to E motif of the F. columnare G(4) Map and its low level of identity with other reported zinc-containing metalloproteases may imply that the membrane-associated zinc metalloprotease of F. columnare G(4) represents a new family of zincins. The gene encoding prolyl oligopeptidase (Pop), a serine proteinase, is 2352 bp in length, coding for 649 aa. Sequence homology analysis revealed that the Pop is also novel as it has <50% identity with other reported prolyl oligopeptidase family proteins. The present study represents the first to employ anti-fish bacterial OMP sera to screen genes of membrane-associated proteases of fish pathogenic bacteria, and to provide necessary information for the examination of the role of the two genes in the infection and pathogenesis of F. columnare.

A TPR-family membrane protein gene is required for light-activated heterotrophic growth of the cyanobacterium Synechocystis sp PCC 6803

The unicellular cyanobacterium Synechocystis sp. PCC6803 can grow heterotrophically in complete darkness, given that a brief period of illumination is supplemented every day (light-activated heterotrophic growth, LAHG), or under very weak ( < 0.5 mumol m(-2) s(-1)) but continuous light. By random insertion of the genome with an antibiotic resistance cassette, mutants defective in LAHG were generated. In two identical mutants, sll0886, a tetratricopeptide repeat (TPR)-family membrane protein gene, was disrupted. Targeted insertion of sll0886 and three downstream genes showed that the phenotype was not due to a polar effect. The sll0886 mutant shows normal photoheterotrophic growth when the light intensity is at 2.5 mumol m(-2) s(-1) or above, but no growth at 0.5 mumol m(-2) s(-1). Homologs to sll0886 are also present in cyanobacteria that are not known of LAHG. sll0886 and homologs may be involved in controlling different physiological processes that respond to light of low fluence. (C) 2003 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.

Fracture properties of silicon carbide thin films by bulge test of long rectangular membrane

This paper reports the mechanical properties and fracture behavior of silicon carbide (3C-SiC) thin films grown on silicon substrates. Using bulge testing combined with a refined load-deflection model of long rectangular membranes, which takes into account the bending stiffness and prestress of the membrane material, the Young's modulus, prestress, and fracture strength for the 3C-SiC thin films with thicknesses of 0.40 and 1.42 mu m were extracted. The stress distribution in the membranes under a load was calculated analytically. The prestresses for the two films were 322 +/- 47 and 201 +/- 34 MPa, respectively. The thinner 3C-SiC film with a strong (111) orientation has a plane-gstrain moduli of 415 +/- 61 GPa, whereas the thicker film with a mixture of both (111) and (110) orientations exhibited a plane-strain moduli of 329 +/- 49 GPa. The corresponding fracture strengths for the two kinds of SiC films were 6.49 +/- 0.88 and 3.16 +/- 0.38 GPa, respectively. The reference stresses were computed by integrating the local stress of the membrane at the fracture over edge, surface, and volume of the specimens and were fitted with Weibull distribution function. For the 0.40-mu m-thick membranes, the surface integration has a better agreement between the data and the model, implying that the surface flaws are the dominant fracture origin. For the 1.42-mu m-thick membranes, the surface integration presented only a slightly better fitting quality than the other two, and therefore, it is difficult to rule out unambiguously the effects of the volume and edge flaws.

MEMBRANE-BASED FIBER BRAGG GRATING PRESSURE SENSOR WITH HIGH SENSITIVITY

A fiber Bragg grating (FBG) pressure sensor packaged by using a hard core in the membrane is presented. By utilizing the unique membrane-based FBG packagine method, its pressure sensitivity has been effectively enhanced. The pressure sensitivity of the FBG reaches 5.75 X 10(-3)/MPa within the pressure range of 0.0.16 Mpa. (C) 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51 1279-1281, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24335

Silicon membrane resonant-cavity-enhanced photodetector

A Si resonant-cavity-enhanced (RCE) photodiode was fabricated on a silicon membrane. The Si membrane was formed by etching from the back side of the silicon-on-insulator substrate with the buried SiO2 layer as etch-stop layer. A gold layer was deposited serving as an electrode layer and bottom mirror of the RCE photodiode. The photodiode had an external quantum efficiency of 33.8% at the resonant wavelength of 848 nm and a full width at half maximum (FWHM) of 17 nm. The responsivity was 4.6 times that of a conventional Si p-i-n photodiode with the same absorption layer thickness. (c) 2005 American Institute of Physics.

Si-based membrane resonant cavity enhanced photodetectors

Si-based membrane RCE photodetectors were introduced. The RCE photodiodes were fabricated on silicon membranes formed from SOI substrate. Compared with the conventional p-i-n photodiode, the responsivity has a threefold enhancement.

A NOVEL ODOR SENSOR COATED WITH A LIPID-MEMBRANE

In this paper, an interdigital electrode lipid film odour sensor (ILOS) is designed, fabricated and tested. It is made from a microfabricated chemiresistor coated with a synthetic multibilayer film. Nine odorants in gas phase at room temperature have been detected using the odour sensor. For most of the odorants, the relation between the response of the ILOS and odorant concentration obeys Stevens' power law, and there is a good correlation between the minimum odorant concentrations that give rise to a change of the sensor's conductance and human olfactory thresholds.

应用负载型纳米铁去除饮用水中砷的研究

砷是毒性最强的元素之一，水体中砷的污染己经引起人们广泛的关注。我国的新疆、内蒙、山西和台湾等省和地区地下水砷含量严重超标。全球共有5,000多万人遭受高砷饮用水的威胁，其中中国有1,500多万，是饮用水砷污染最严重的国家之一。WHO推荐饮用水砷的最高允许浓度从原来的50 µg•L-1已降至10 µg•L-1。更为严格的砷卫生标准的颁布，对作为饮用水源的地下水中的砷去除工艺提出了更高的要求。吸附法除砷比膜法、混凝法和离子交换法更安全、简便，是砷去除工艺中最有效的方法之一。 首先，本研究通过优化制备条件（包括炭种类的选择、炭的粒径大小、还原剂的浓度及滴定速率、反应温度、铁盐的种类及浓度、分散剂的比例及浓度），制备了负载型纳米铁。考虑到砷的去除效率、工程应用的可行性以及经济性，最优的制备条件如下：选用粒径为20~40目煤质炭，在室温、一定的分散剂比例及浓度，0.2 M KBH4滴速为20 d•min-1时所制备的Fe/炭为82.0 mg•g-1；纳米铁在活性炭孔内呈针状，其直径为30~500 nm，长度为1,000~2,000 nm。绝大多数的铁都负载到活性炭内部，这在处理水时铁不流失很重要。 其次，利用制备的负载型纳米铁作吸附载体，进行了饮用水中As(Ⅴ)的吸附去除实验。研究了该吸附剂对As(Ⅴ)的吸附等温线、动力学以及影响动力学的各种因素（包括As(Ⅴ)的不同初始浓度、吸附剂用量、pH值、共存离子和不同温度）、pH值、共存离子等环境条件对As(Ⅴ)去除的影响；以及吸附剂的再生及再生后的吸附效率等。研究发现在前12 h内吸附较快，72 h时达到了平衡。用Langmuir 吸附等温式估算出As(Ⅴ)的吸附量为12.0 mg•g-1。该吸附剂在pH 6.5， (25±2)℃， As(Ⅴ)初始浓度为2 mg•L-1，吸附剂用量为1.0 g•L-1时，As(Ⅴ)的去除率为75.2%；当把吸附剂的用量增加到1.5 g•L-1时，As(Ⅴ)的去除率可达99.9%以上。吸附剂可以用0.1M的NaOH浸泡12 h后即可再生，再生效率较高。常见的阴离子中PO43-、SiO32-对As(Ⅲ)的去除抑制较大，而SO42-、CO32-、C2O42-等离子对砷的去除影响较小。Fe2+对As(Ⅲ)的吸附抑制作用较大而其它阳离子影响不大。吸附剂可用0.1 M NaOH 有效再生，并且具有良好的机械性能。实验室初步实验数据表明，该吸附剂对饮用水除砷具有较好的应用前景。 第三，利用实验室制备的负载型纳米铁对饮用水中As(Ⅲ)的吸附去除也进行了研究。考察了吸附等温线、动力学以及影响动力学的各种因素、pH值、共存离子等环境条件对As(Ⅲ)去除的影响；以及吸附剂的再生及再生后的吸附效率等。研究发现，该吸附剂在pH 6.5， (25±2)℃， As(Ⅲ)初始浓度为2 mg•L-1，吸附剂用量为1.0 g•L-1时， 对As(Ⅲ)的去除率为99.8%；其吸附容量为1.996mg•g-1。吸附过程中部分As(Ⅲ)被氧化。与As(Ⅴ)的吸附相比，该吸附剂对As(Ⅲ)的效率比较高-而常见的其它除砷吸附剂如载铁纤维棉等，对As(Ⅴ)的效率比As(Ⅲ)高，为有效去除As(Ⅲ)，常常需要专门加上氧化这一过程。 最后，利用负载型纳米铁对饮用水中As(Ⅲ) 的氧化性能进行考察，发现该吸附剂不但能够有效吸附去除饮用水中的砷，而且还能把As(Ⅲ)有效地氧化为As(Ⅴ)。经过对吸附剂的构成组分分析发现，活性炭表面因富含多种官能团而对三价砷的氧化作用最大；其次是纳米铁也能把As(Ⅲ)氧化为As(Ⅴ)。