鲍曼不动杆菌LpxC的同源模建及分子对接

鲍曼不动杆菌已成为最普遍的医院致病菌,且耐药情况严峻.LpxC作为新抗菌药物靶点被大量研究,但鲍曼不动杆菌LpxC晶体尚未解析得到,基于其结构的药物设计等工作无法开展.以铜绿假单胞菌LpxC晶体结构为模板,通过同源模建方法获得鲍曼不动杆菌LpxC结构模型.较好的Ramachandran plot分布和Profile-3D结果验证了模型的合理性.用分子动力学模拟优化鲍曼不动杆菌LpxC模型,修补部分不合理构象.后续分子对接结果显示S构型的苄氧乙酰基羟肟酸类抑制剂比R构型分子能更有效地结合在F191,H237和K238组成的较浅口袋中,这可能是S构型抑制剂活性更高的主要因素,模拟结果与实验数据吻合较好.     

Polymyxin B Combined with Minocycline: A Potentially Effective Combination against blaOXA-23-harboring CRAB in In Vitro PK/PD Model

Polymyxin-based combination therapy is commonly used to treat carbapenem-resistant Acinetobacter baumannii (CRAB) infections. In the present study, the bactericidal effect of polymyxin B and minocycline combination was tested in three CRAB strains containing bla_OXA-23 by the checkerboard assay and in vitro dynamic pharmacokinetics/pharmacodynamics (PK/PD) model. The combination showed synergistic or partial synergistic effect (fractional inhibitory concentration index ≤0.56) on the tested strains in checkboard assays. The antibacterial activity was enhanced in the combination group compared with either monotherapy in in vitro PK/PD model. The combination regimen (simultaneous infusion of 0.75 mg/kg polymyxin B and 100 mg minocycline via 2 h infusion) reduced bacterial colony counts by 0.9–3.5 log₁₀ colony forming units per milliliter (CFU/mL) compared with either drug alone at 24 h. In conclusion, 0.75 mg/kg polymyxin B combined with 100 mg minocycline via 2 h infusion could be a promising treatment option for CRAB bloodstream infections.     

不动杆菌静息细胞催化拆分外消旋环戊酮醇乙酸酯反应条件的优化

 考察了反应条件对不动杆菌Acinetobactersp．YQ231催化外消旋环戊酮醇乙酸酯对映选择性水解的反应速度和对映选择性的影响．确定的最佳酶反应条件为pH8．0，温度50℃．不同乳化剂对对映选择性的影响不同，以壬基酚聚氧乙烯醚的效果最好，当其加入量为15g／L时，反应的对映选择性最高．产物环戊酮醇对酶活性有显著的抑制作用．细胞中的酯酶优先水解（R）－环戊酮醇乙酸酯，生成（R）－环戊酮醇，在底物浓度为250mmol／L时，对映体比率（E值）可达50．     

Role of the shape of various bacteria in their separation by Microthermal Field-Flow Fractionation

The steady-state movement of the spherical and non-spherical particles, such as prolate or oblate rotational ellipsoids, cylinders, or parallelepipeds, suspended in a liquid and exposed to a unidirectional temperature gradient, is analyzed theoretically. The differences in the ratios of the rotational to translational diffusion coefficients of the non-spherical to spherical particles, the heterogeneity of thermal conductivity of the particle body, and the heterogeneity in surface chemical nature make possible to separate the particles according to differences in shape. Preliminary experimental separations of Gram-positive and Gram-negative, nearly spherical and rod-shaped bacteria performed by Microthermal Field-Flow Fractionation confirmed that the fractionation of the cells according to differences in shape is possible.     

固定化细菌去除苯甲酸类化合物的研究

用富集培养法，从工业废水中分离到能以苯甲酸类化合物为唯一碳源和能源而生长的细菌不动杆菌ＢＪ１和产碱杆菌ＳＢ１。用海藻酸钙共固定化的ＢＪ１和ＳＢ１菌株于３０℃培养７２ｈ以后，模拟工业废水中１ｇ／Ｌ的苯甲酸，邻羟基苯甲酸，间羟基苯甲酸，以羟基苯甲酸，邻苯二甲酸和苯乙酸的去除率分别为８９％，９８％，９７％，１００％，９０％和６１％。     

Determination of organophosphorus aromatic nitro insecticides by using electric-field cell orientation in microbial suspensions

We examined the effect of the cellular metabolism of the organophosphorus aromatic nitro insecticides metaphos and sumithion on the electro-physical properties (EPPs) of Pseudomonas putida C-11, P. putida BA-11, and Acinetobacter calcoaceticum A-122 suspensions. We used the dependences of cell-suspension absorbance changes induced by electric-field orientation on the orienting-field frequency in the range 10-10,000 kHz. Substantial orientational-spectrum changes, caused by insecticide action, occurred at frequencies of 10-1000 kHz. The plots of electro-optical effect versus insecticide-concentration were linear over the following concentration ranges: 0.5-3.0 mM metaphos and 0.5-3.5 mM sumithion for P. putida C-11 and BA-11; and 0.5-2.0 mM metaphos and 0.5-2.5 mM sumithion for A. calcoaceticum A-122. We discuss the possibility of developing a biosensor-method based on the measurement of cell-suspension orientational spectra (OS).     

Semicontinuous production of lipase by Acinetobacter radioresistens in presence of nonwoven fabric

The effect of a hydrophobic nonwoven fabric on the lipase production by Acinetobacter radioresistens was investigated with semicontinuous culture. The fermentation medium contained n-hexadecane as the carbon source. The nonwoven fabric was made from nylon 6 and coated with an acrylic resin. Equipping the nonwoven fabric around the baffles of a 2.5-L agitated fermentor could provide a fine dispersion of n-hexadecane, thus enhancing lipase production. The improvement on lipase yield by using the nonwoven fabric was found to be comparable to that of using an emulsifier (gum arabic). Compared with the corresponding culture in the absence of nonwoven fabric, the employment of the nonwoven fabric could significantly enhance both lipase yield and volumetric productivity.     

Structural and immunochemical analysis of the lipopolysaccharide from Acinetobacter lwoffii F78 located outside Chlamydiaceae with a Chlamydia-specific lipopolysaccharide epitope

Chemical analyses, NMR spectroscopy, and mass spectrometry were used to elucidate the structure of the rough lipopolysaccharide (LPS) isolated from Acinetobacter lwoffii F78. As a prominent feature, the core region of this LPS contained the disaccharide alpha-Kdo-(2-->8)-alpha-Kdo (Kdo=3-deoxy-d-D-manno-oct-2-ulopyranosonic acid), which so far has been identified only in chlamydial LPS. In serological investigations, the anti-chlamydial LPS monoclonal antibody S25-2, which is specific for the epitope alpha-Kdo-(2-->8)-alpha-Kdo, reacted with A. lwoffii F78 LPS. Thus, an LPS was identified outside Chlamydiaceae that contains a Chlamydia-specific LPS epitope in its core region.     

Degradation of Perfluorooctane Sulfonamide by Acinetobacter Sp. M and Its Extracellular Enzymes

The Acinetobacter sp. strain M isolated from a contaminated soil sample in Jiangsu Province of China was found to be able to degrade perfluorooctane sulfonamide (PFOSA) effectively. Fluoride anion (F^?) released from PFOSA degradation was detected by ion chromatography, and showed positive correlation to the growth curve of Acinetobacter sp. strain M. The PFOSA degradation efficiency of strain M was approximately 27 %, as assessed by GC analysis. It was shown that enzymes localized outside of cells of Acinetobacter sp. strain M catalyzed the degradation of PFOSA. This further indicates a possibly new (multi‐step/pathway) mechanism for PFOSA degradation. It revealed that the extracellular enzyme of the Acinetobacter strain M preferentially cleaves carbon‐carbon and carbon‐fluorine bonds instead of destroying the carbon‐sulfur bond. The growth condition for Acinetobacter sp. strain M was optimized at 30 °C and pH 7.0 in the presence of 2000 mg L^?1 of PFOSA and 0.5 % (v/v) of Tween‐20. The optimal PFOSA degradation time was found to be 12 h, with a degradation efficiency of 76 % by extracellular enzymes in strain M as determined by GC analysis. The result may provide potential applications for biodegradition of perfluoro organic compounds, such as derivatives of perfluorooctane (C8).     

Synthesis and investigation of binding interactions of 1,4-benzoxazine derivatives on topoisomerase IV in Acinetobacter baumannii$

Abstract

Acinetobacter baumannii has emerged as an important pathogen for nosocomial infections having high morbidity and mortality. This pathogen is notorious for antimicrobial resistance to many common antimicrobial agents including fluoroquinolones, which have both intrinsic and acquired resistance mechanisms. Fluoroquinolones targeting the bacterial topoisomerase II (DNA gyrase and Topo IV) show potent broad-spectrum antibacterial activity by the stabilization of the covalent enzyme–DNA complex. However, their efficacy is now being threatened by an increasing prevalence of resistance. Fluoroquinolones cause stepwise mutations in DNA gyrase and Topo IV, having alterations of their binding sites. Furthermore, the water–Mg⁺² bridge, which provides enzyme–fluoroquinolone interactions, has a significant role in resistance. In this study, 13 compounds were synthesized as 1,4-benzoxazine derivatives which act as bacterial topoisomerase II inhibitors and their antibacterial activities were determined against multi-drug resistant Acinetobacter strains which have ciprofloxacin (CIP) resistant and GyrA mutation. Afterwards we performed docking studies with Topo IV (pdb:2XKK) of these compounds to comprehend their binding properties in Discovery Studio 3.5. The results of this study show significant conclusions to elucidate the resistance mechanism and lead to the design of new antibacterial agents as bacterial topoisomerase II inhibitors.