一株广盐性蛭弧菌的生物学特性

【背景】蛭弧菌有裂解水产养殖中常见致病菌的能力,具有重要的潜在应用价值,但在实际应用中,存在着菌株生长条件与应用环境不相符而导致效果差乃至无效果等问题。因此获得适应范围宽的蛭弧菌甚为关键。【目的】筛选出一株广盐性蛭弧菌以利推广应用;提升蛭弧菌蛭质体密度以利保存。【方法】以枯草芽孢杆菌为宿主,于浅滩水域分离纯化出一株广盐性蛭弧菌;对该广盐性蛭弧菌菌株进行分子生物学鉴定;之后探究其生物学特性及裂解性能,并研究谷氨酸钠、Ca~(2+)和Mg~(2+)、吲哚等影响蛭质体密度的因素。【结果】分离获得一株广盐性蛭弧菌BDN-1,其适宜温度、盐度和pH范围分别为20-30°C、0.5%-3.0%、6.0-8.5;BDN-1对30株受试菌的裂解率为86.7%,对其中16株受试弧菌裂解率为87.5%;谷氨酸钠、吲哚、Ca~(2+)和Mg~(2+)对BDN-1蛭质体密度有提升作用。【结论】研究结果提供了一株裂解能力强且海淡水均可应用的蛭弧菌菌株,查明了其生物学特性及影响其蛭质体密度的因素,为蛭弧菌的高效利用奠定了基础。     

人粪便中分离的噬菌蛭弧菌生物学特性的研究

本文研究了人粪便中分离的噬菌蛭弧菌的生物学特性,测定了它们的生长曲线,并利用微孔滤膜过滤和机械振荡的方法,研究了它们的吸附和穿入动力学,发现链霉素、庆大霉素和卡那霉素能抑制蛭弧菌的吸附;青霉素不影响蛭弧菌的吸附和穿入,但抑制蛭弧菌在宿主内的生长过程。从人粪中分出的噬菌蛭弧菌不仅能裂解大部分需氧的革兰氏阴性菌,而且在微氧条件下也能裂解厌氧菌中的二株脆弱拟杆菌。我们发现一株人粪便中分出的噬菌蛭弧菌能形成蛭弧菌囊体——它的休眠态,它对高热、紫外线照射和真空干燥的耐受力较相应的繁殖体强,看来它是蛭弧菌保持生命期限的一种方式。     

两种培养基对对虾苗池海洋蛭弧菌的分离及其多样性分析

【目的】明确海水(Sw)和聚蛋白胨20(Pp20)两种双层琼脂培养基对海洋蛭弧菌的分离计数效果,了解对虾苗池可培养海洋蛭弧菌多样性。【方法】采用双层平板法,比较Sw和Pp20培养基对2株海洋蛭弧菌和对虾苗池未知海洋蛭弧菌的计数效果。通过宿主范围测试和16S rRNA基因序列分析评估两种培养基分离苗池海洋蛭弧菌的多样性。【结果】宿主菌含量高时,Sw培养基对两株已知海洋蛭弧菌的计数值均显著高于(P0.05)Pp20。Sw和Pp20培养基从同一苗池水样分别分离得到21和22株蛭弧菌。根据宿主裂解范围差异,43株分离物可分为15种裂解模式,其中Sw和Pp20培养基各分离到12和8种。16S rRNA基因序列分析表明,所有分离物都被鉴定为噬菌弧菌属(Bacteriovorax)菌株,并可分为6个类群,Sw和Pp20培养基分别分离到6和4个类群。【结论】Sw培养基在分离计数海洋蛭弧菌及其多样性检测上效果均优于Pp20;对虾苗池可培养海洋蛭弧菌具有较高多样性,并以类群XIII、X及一个潜在新类群为优势种群。     

噬菌蛭弧菌对鱼类常见致病菌裂解作用的研究

调查了北京地区２５份水样,其中２４份检出噬菌蛭弧菌。本次试验选用４株鱼类主要致病菌为宿主菌,检出的蛭弧菌对上述４种细菌的裂解范围有所不同。其中嗜水气单胞菌可被全部检出的蛭弧菌裂解（２４／２４）,其他３株菌仅部分被裂解,依次为肠型点状气单胞菌（１７／２４）,荧光假单胞菌（９／２４）,鳗弧菌（７／２４）。本次试验直接从水样中检出６株对４种宿主菌均有裂解作用的蛭弧菌,为进一步利用蛭弧菌防治鱼类常见细菌性疾病提供了可用资料。     

噬菌蛭弧菌对鱼类常见致病菌裂解作用的研究*

调查了北京地区２５份水样,其中２４份检出噬菌蛭弧菌。本次试验选用４株鱼类主要致病菌为宿主菌,检出的蛭弧菌对上述４种细菌的裂解范围有所不同。其中嗜水气单胞菌可被全部检出的蛭弧菌裂解（２４／２４）,其他３株菌仅部分被裂解,依次为肠型点状气单胞菌（１７／２４）,荧光假单胞菌（９／２４）,鳗弧菌（７／２４）。本次试验直接从水样中检出６株对４种宿主菌均有裂解作用的蛭弧菌,为进一步利用蛭弧菌防治鱼类常见细菌性疾病提供了可用资料。     

噬菌蛭弧菌生物特性研究进展

本文介绍了噬菌蛭弧菌的培养特性,温度对噬菌蛭弧菌的影响,噬菌蛭弧菌的生化特征,感染宿主的机制,在死的宿主菌中生长的特性,宿主的特异性以及噬菌蛭弧菌对致病菌的生物净化作用等生物特性的研究进展。研究认为,噬菌蛭弧菌是自然环境(水、土壤)中致病微生物的生物拮抗体,且极有可能利用它的寄生和溶解宿主菌细胞的特殊性,对环境水体的生物净化。     

蛭弧菌的分离及其生长条件和裂解能力的研究

噬菌蛭弧菌具有裂解病原菌、净化水体的功效,从海洋环境中分离到4株Bh04系列蛭弧菌,对其生长条件进行了测定,同时研究了它们对61株菌株的裂解能力。结果表明,在1%～3%的盐度范围内,蛭弧菌均可生长,最适盐度为3%;在15～30℃温度条件下蛭弧菌也可生长,但最适培养温度为20-25℃;只有在使用活的宿主菌的培养条件下,蛭弧菌才能生长。4株蛭弧菌分别可裂解21、24、40、43株菌,各占总试验菌数(61)的34.4%、39.3%、65.6%和70.5%。4株蛭弧菌一起,则可裂解55菌株,占总试验菌株的90.2%。研究结果揭示了蛭弧菌在消除海洋环境中有害细菌方面的潜在应用价值。     

鱼病蛭弧菌的微生态学初步研究

本次以鲫鱼出血性腹水病病原菌点状产气单胞菌（Ａｅｒｏｍｏｎａｓ Ｐｕｎｃｔａｔａ）为宿主菌。从自然界分离获得６株噬菌蛭弧菌菌株,它们具有噬菌蛭弧菌的生物学特性。研究表明,这６株蛭弧菌的最适培养条件为温度２５￣２８℃,ｐＨ７．２,有溶菌性,能裂解多种鱼类病原菌。其中对蛭弧菌Ｂｄｓ－４菌株在实验条件下对病原菌的自然净化作用等方面进行了研究。说明蛭弧菌是精养鱼糖水体中某些致病菌的自然净化的重要生物因素之     

海洋蛭弧菌的分离鉴定及其对副溶血弧菌的作用

蛭弧菌广泛存在于自然水体, 具有噬菌的特性, 对水体中细菌数量控制具调节作用。以副溶血弧菌为宿主菌, 利用双层琼脂法, 从海洋水体中分离出15株具有噬菌作用的细菌, 对形成噬菌斑能力最强的1株菌株进行特异性16S rDNA扩增, 确认为蛭弧菌, 命名为Bd-M1。Bd-M1对大多数海水养殖动物病原菌有裂解作用, 裂解率在90%(20/22)以上, 模拟水环境实验发现, 蛭弧菌对副溶血弧菌有较强的裂解和净化作用, 102 h内能使副溶血弧菌从3.0′108 CFU/mL下降到8.7×103 CFU/mL。动物实验表明蛭弧菌能有效预防对虾弧菌病的发生, 表明蛭弧菌有望成为水产动物疾病防治的一种有效的生物制剂。     

噬菌蛭弧菌对嗜水气单胞菌裂解作用的研究

本文报道了8株噬菌蛭弧菌对河水中分离的9株嗜水气单胞菌的裂解作用。结果发现,噬菌蛭弧菌Bd32的裂解率为77.78％;Bd83、Bd98的裂解率为88.89％,其余5株噬菌蛭弧菌对9株嗜水气单胞菌全部裂解。     

Calcium in fungi

Abstract. Recently much experimental evidence has accumulated concerning intracellular calcium and its fundamental role as a regulator in eukaryotic cells. The literature relating to Ca²⁺ in fungi is large and diverse and this paper draws together the available information and discusses the particular functions of the ion in this group of organisms.
Uptake mechanisms in fungi are considered with special reference to the effect of Ca²⁺ on permeability and the systems responsible for transport of ions, sugars and amino acids. Discussion of the subcellular locations and distribution of Ca²⁺ is accompanied by a critique of methodology used in determination of subcellular sites of Ca²⁺ in fungi. The role of Ca²⁺ in morphogenesis in fungi is considered with particular reference to selected groups.     

Isolation and characterization of cytoplasmic NADP+-malic enzyme from Lupinus luteus leaves

NADP⁺-dependent malic enzyme (L-malate : NADP⁺ oxidoreductase, decarboxylating, EC 1.1.1.40) was extracted from the leaves of yellow lupine. The purification procedure included fractionation with (NH₄)₂SO₄ and Sephadex G-25 chromatography, followed by purification on DEAE-cellulose and Sephadex G-200 columns. The enzyme was purified 122-fold. The enzyme affinity towards L-malate was found to be significantly higher with Mn²⁺ than with Mg²⁺. The Hill coefficient for Mg²⁺ depended on concentration and was 1.6 for the lower and 3.9 for the higher concentrations. The dependence of the enzyme activity on NADP⁺ followed a hyperbolic curve. K_m values and Hill coefficients for NADP⁺ were similar with both Mn²⁺ and Mg²⁺. The enzyme activity was strictly dependent on divalent cations and followed a sigmoidal curve at least for Mg²⁺. The enzyme had 4-fold higher affinity towards Mn²⁺ than towards Mg²⁺, the K_m values being 0.3 and 1.15 m M respectively. Of several tested organic acids, oxalate was the most effective inhibitor followed by oxaloacetate while succinate was the strongest activator.     

The effect of Sirt1 deficiency on Ca2+ and Na+ regulation in mouse ventricular myocytes

This study addressed the hypothesis that cardiac Sirtuin 1 (Sirt1) deficiency alters cardiomyocyte Ca²⁺ and Na⁺ regulation, leading to cardiac dysfunction and arrhythmogenesis. We used mice with cardiac‐specific Sirt1 knockout (Sirt1^?/?). Sirt1^flox/flox mice were served as control. Sirt1^?/? mice showed impaired cardiac ejection fraction with increased ventricular spontaneous activity and burst firing compared with those in control mice. The arrhythmic events were suppressed by KN93 and ranolazine. Reduction in Ca²⁺ transient amplitudes and sarcoplasmic reticulum (SR) Ca²⁺ stores, and increased SR Ca²⁺ leak were shown in the Sirt1^?/? mice. Electrophysiological measurements were performed using patch‐clamp method. While L‐type Ca²⁺ current (I_{Ca, L}) was smaller in Sirt1^?/? myocytes, reverse‐mode Na⁺/Ca²⁺ exchanger (NCX) current was larger compared with those in control myocytes. Late Na⁺ current (I_{Na, L}) was enhanced in the Sirt1^?/? mice, alongside with elevated cytosolic Na⁺ level. Increased cytosolic and mitochondrial reactive oxygen species (ROS) were shown in Sirt1^?/? mice. Sirt1^?/? cardiomyocytes showed down‐regulation of L‐type Ca²⁺ channel α1c subunit (Cav1.2) and sarcoplasmic/endoplasmic reticulum Ca²⁺ ATPase 2a (SERCA2a), but up‐regulation of Ca²⁺/calmodulin‐dependent protein kinase II and NCX. In conclusions, these findings suggest that deficiency of Sirt1 impairs the regulation of intracellular Ca²⁺ and Na⁺ in cardiomyocytes, thereby provoking cardiac dysfunction and arrhythmogenesis.     

The Ca 2+ pumps and the Na + / Ca 2+ exchangers

The Ca 2+ ATPases or Ca 2+ pumps transport Ca 2+ ions out of the cytosol, by using the energy stored in ATP. The Na + / Ca 2+ exchanger uses the chemical energy of the Na + gradient (the Na + concentration is much higher outside than inside the cell) to remove Ca 2+ from the cytosol. Ca 2+ pumps are found in the plasma membrane and in the endoplasmic reticulum of the cells. The pumps are probably present in the membrane of other organelles, but little experimental information is available on this matter. The Na + / Ca 2+ exchangers are located on the plasma membrane. A Na + / Ca 2+ exchanger was found in the mitochondria, but very little is known on its structure and sequence. These transporters control the Ca 2+ concentration in the cytosol and are vital to prevent Ca 2+ overload of the cells. Their activity is controlled by different mechanisms, that are still under investigation. A number of the possible isoforms for both types of proteins has been detected.© Kluwer Academic Publishers     

Effects of α2-Adrenergic Agonists and Antagonists on Photoreceptor Membrane Currents

Type B photoreceptors of the nudibranch mollusc Hermissenda crassicornis receive excitatory synaptic potentials (EPSPs) whose frequency is controlled by potential changes of a neighboring cell known as the S optic ganglion cell which is thought to be electrically coupled to the presynaptic source of these EPSPs, the E optic ganglion cell. The frequency of the EPSPs increases when a conditioned stimulus (light) is paired with an unconditioned stimulus (rotation) during acquisition of a Pavlovian conditioned response. The results of the present study are consistent with an adrenergic origin for these EPSPs. Noradrenergic agonists (greater than 100 microM), norepinephrine and clonidine, only slightly depolarize the type B cell but clearly prolong its depolarizing response to light. Serotonin, by contrast, causes hyperpolarization of the type B cell's resting potential as well as after a light step. Clonidine reduces voltage-dependent outward K+ currents (IA, an early current, ICa2+-K+, a late Ca2+-dependent current) that control the type B cell's excitability (and thus its light response and membrane potential). These effects of clonidine are reduced or blocked by the alpha 2-receptor antagonist, yohimbine (0.5 microM), but not the alpha 1-blocker, prazosin. The same yohimbine concentration also blocked depolarizing synaptic excitation of the type B cell in response to depolarization of a simultaneously impaled S optic ganglion cell. Histochemical techniques (both the glyoxylic acid method of de la Torre and Surgeon and the formaldehyde-induced fluorescence or Falck-Hillarp method) demonstrated the presence of a biogenic amine(s) within a single neuron in each optic ganglion as well as three or four cells within the vicinity of previously identified visual interneurons. No serotonergic neurons were found within the optic ganglion or in proximity to visual interneurons. A clonidine-like synaptic effect on type B cells, therefore, could amplify conditioning-specific changes of membrane currents by increasing type B depolarization and possibly, as well, by elevating intracellular second messengers.     

Effect of aluminium on the NAD+ kinase activity of Euglena gracilis grown heterotrophically

The effect of 2 mM AlCl3 on NAD+ kinase (E.C. 2.7.1.23) activity was studied using Euglena gracilis strain Z grown heterotrophically in darkness at pH 3.5 in the presence of lactate as sole carbon source. The Al-treatment slowed down the culture growth and suppressed the peak of NAD+ kinase activity, which characterizes the beginning of the exponential phase of growth of the control cell cultures. There are two possible explanations of the Al effect: it 1) either prevents the enzyme activation by the Ca-calmodulin (CaM) complex; or 2) suppresses the CaM-dependent NAD+ kinase form. In Euglena cells, a part of the NAD+ kinase activity is enhanced by EGTA and lowered by Ca2+: this peculiar NAD+ kinase activity is unaffected by the Al treatment. This revised version was published online in July 2006 with corrections to the Cover Date.     

Anion-sensitive ATPase activity and proton transport in isolated vacuoles of species of the CAM genus Kalanchoë

Vacuoles were isolated from leaves of Kalanchoë daigremontiana Hamet et Perrier de la Bathie, and the ionic sensitivity of the vacuolar ATPase was studied in vacuole homogenates desalted on Sephadex G-25. The ATPase activity was dependent on the presence of divalent cations (Mg²⁺≥ Mn²⁺≥ Ca²⁺, Co²⁺; Zn²⁺ had no effect). Mg²⁺-dependent ATPase activity was stimulated by anions (Cl^? > malate²⁺, HCO^?₃), with maximal stimulation at concentrations above 50 mM. Mg²⁺-Dependent activity was inhibited by NO^?₃ above 2 mM, but no saturation was observed up to 100 mM. No stimulation by K⁺ or Na⁺ was detected; stimulation by NH⁺₄ was abolished by 0.01% (w/v) Triton X-100, suggesting that the NH⁺₄ effect was due to the permeability of vacuolar membrane vesicles to NH₃. Trans-tonoplast electrical potentials (Δψ) and intra-vacuolar pH were measured with glass microelectrodes and antimony covered glass micro-pH-electrodes, respectively. Free vacuofes isolated from Kalanchoë tubiflora (Harv.) Hamet were slightly positive with respect to the suspension medium. This Δψ was insensitive to the protonophore FCCP and depolarized by about 4 mV on addition of 50 mM KCl, still remaining about +5 mV. Upon addition of 7 mM Mg-ATP, vacuoles showed an FCCP-sensitive increase of Δψ from +9.2 ± 2.8 (13) to +17.8 ± 3.7 (12) mV [given as x?± sd (n)] and an internal acidification from pH 5.4 ± 0.2 (11) to pH 4.3 ± 0.4 (12). Mg-ADP and ATP without Mg²⁺ had no effect on Δψ. It is concluded that the H4 pumping at the tonoplast is due to the functioning of the anion-sensitive vacuolar ATPase and that this is an essential part of the mechanism of nocturnal acid accumulation in CAM.     

Kinetic Characterization of Ca2+ Transport in Synaptic Membranes

Lysed synaptosomal membranes were prepared from brain cortices of HA/ICR Swiss mice, and the ATP-stimulated Ca2+ uptake, Ca2+-stimulated Mg2+-dependent ATPase activity, and the Ca2+-stimulated acyl phosphorylation of these membranes were studied. The Km values for free calcium concentrations ([Ca2+]f) for these processes were 0.50 microM, 0.40 microM, and 0.31 microM, respectively. Two kinetically distinct binding sites for ATP were observed for the ATP-stimulated Ca2+ uptake and the Ca2+-stimulated Mg2+-ATPase activity. The high-affinity Km values for ATP for these two processes were 16.3 microM and 28 microM, respectively. These results indicate that the processes studied operate in similar physiological concentration ranges for the substrates [Ca2+]f and ATP under identical assay conditions and, further, that these processes may be functionally coupled in the membrane.     

A model for cation content of plants based on surface potentials and surface charge densities of plant membranes

The model presented takes into account the interaction between the negatively charged membranes and macromolecules and the cations. A central postulate is that a constant average surface charge density (σ) as well as a constant average surface potential (Ψ) is conserved under different ionic conditions. The model makes it possible to predict the size of σ and Ψ from measurements of Na, K, Mg and Ca content in plant tissues of the same age but grown under two different ionic conditions (e.g. high and low K⁺). Assumptions were made about the relative amounts of free and bound Ca²⁺ and σ and Ψ were calculated from values in the literature. In all cases σ (and Ψ) are predicted to be higher for shoot (−29 to −96 mC m⁻²) than for root membranes (−14 to −27 mC m⁻²). In most cases the predicted σ falls within the range determined experimentally for biological membranes.