Isolation and complete genome sequence of a novel virulent mycobacteriophage,CASbig

<正>Dear Editor,Bacteriophages are powerful tools for investigating and manipulating their hosts(Fernandes et al.,2014).This holds particularly true for mycobacteriophages,which have facilitated the development of mycobacterial genetic systems and have generated tools for the clinical     

The stress-strain relation of the plasma membrane of isolated plant protoplasts

Over periods of up to a few seconds the plasma membrane of isolated rye protoplasts behaves elastically with an area modulus of $\text{230}\text{mN}\text{·}\text{m}{}^{\mathrm{?1}}$. Over longer periods, the area increases with time under large tension and decreases under sufficiently small tension, suggesting that material is incorporated into or depleted from the plane of the membrane.     

Extracellular haemolytic activity of Serratia marcescens

Blood agar medium with dialysis membrane mounted between two layers of agar was applied to study the haemolytic activity of 28 strains of Serratia marcescens. Two kinds of lytic substances differing with their ability to pass through dialysis membrane were found. Haemolytic activity was not detected in cell-free filtrates from liquid cultures. The discrepancies between haemolytic activity in blood agar media and activity of liquid cultures were observed. Stable attachment of bacterial cells to the erythrocytes was not necessary to lysis. The possibility of extracellular haemolysin is discussed.     

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。     

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。     

Characterization of a Small Molecule Inhibitor of Plasminogen Activator Inhibitor Type 1 That Accelerates the Transition into the Latent Conformation

A novel class of small molecule inhibitors for plasminogen activator inhibitor type 1 (PAI-1), represented by AZ3976, was identified in a high throughput screening campaign. AZ3976 displayed an IC₅₀ value of 26 μm in an enzymatic chromogenic assay. In a plasma clot lysis assay, the compound was active with an IC₅₀ of 16 μm. Surprisingly, AZ3976 did not bind to active PAI-1 but bound to latent PAI-1 with a K_D of 0.29 μm at 35 °C and a binding stoichiometry of 0.94, as measured by isothermal calorimetry. Reversible binding was confirmed by surface plasmon resonance direct binding experiments. The x-ray structure of AZ3976 in complex with latent PAI-1 was determined at 2.4 Å resolution. The inhibitor was bound in the flexible joint region with the entrance to the cavity located between α-helix D and β-strand 2A. A set of surface plasmon resonance experiments revealed that AZ3976 inhibited PAI-1 by enhancing the latency transition of active PAI-1. Because AZ3976 only had measurable affinity for latent PAI-1, we propose that its mechanism of inhibition is based on binding to a small fraction in equilibrium with active PAI-1, a latent-like prelatent form, from which latent PAI-1 is then generated more rapidly. This mode of action, with induced accelerated latency transition of active PAI-1 may, together with supporting x-ray data, provide improved opportunities for small molecule drug design in the hunt for therapeutically useful PAI-1 inhibitors.     

Trypanosoma cruzi: ultrastructural studies of adhesion, lysis and biofilm formation by Serratia marcescens

A few days after blood meal the number of bacteria in the anterior midgut (stomach) of Rhodnius prolixus, a vector of Trypanosoma cruzi, the causative agent of Chagas' disease, increases dramatically. Many of the bloodstream trypomastigotes of the pathogenic protozoan as well as ingested erythrocytes are lysed in the stomach. Incubation of T. cruzi with Serratia marcescens variant SM365, lead to parasite lysis. In the present study, this bacterium rapidly adhered to the protozoan surface through d-mannose recognizing fimbriae and rapidly induced its complete lysis. In contrast, the DB11 variant of the same bacterial species did not adhere and did not induce protozoan lysis. Scanning and transmission electron microscopy revealed that following bacteria-protozoan attachment there is an assembly of long filamentous structures, identified as a biofilm, which connect the protozoan to the bacteria forming bacterial clusters. We conclude that parasite lysis and biofilm formation mechanisms are important for understanding parasite-microbiota interactions in the gut of insect vectors of trypanosomatids.     

Leishmania (Leishmania) chagasi interactions with Serratia marcescens: ultrastructural studies, lysis and carbohydrate effects

Studies on the lysis of L. chagasi caused by the bacteria Serratia marcescens were carried out. In vitro experiments demonstrated that S. marcescens variant SM 365, a prodigiosin pigment producer, lysed this species of Leishmania but variant DB11, a nonpigmented bacteria, was unable to lyse the parasite. High concentrations of d-mannose were found to protect L. chagasi markedly diminishing the lysis by S. marcescens SM 365. Promastigotes of L. chagasi bound the lectin Concanavalin A conjugated with FITC, the fluorescence was intensely found at the base of the flagellum (flagellar pocket). Scanning electron microscopy revealed that the bacteria adherence occurred mainly in the flagellar pocket. S. marcescens SM 365 formed filamentous structures, identified as biofilms, which connect the protozoan to the developing bacterial clusters, in low concentrations of bacteria after 30 min incubation time. We suggest that bacterial mannose-sensitive (MS) fimbriae are relevant to S. marcescens SM 365 in the lysis of L. chagasi.