假单胞菌Hy—1对多房棘球蚴泡块的抑制作用

从成都土壤中分离到一株假单胞菌,编号Hy—1。该菌株为革兰氏阴性需氧短杆菌,具极生丛鞭毛,营呼吸代谢,化能异养;还具有能分解Twccn60,液化明胶,不水解淀粉,产生聚—B—羟基丁酸盐颗粒(PHB)等特性。该菌株的代谢产物对一些革兰氏阳性细菌有较强拮抗作用。Hy—1菌苗对小白鼠多房棘球蚴移植泡块有显著抑制作用,能阻止多房棘球蚴在鼠体内的生长,发育和扩散。初步毒理试验发现Hy—1 对小鼠无急性毒性作用,在体内无存活扩散现象。     

Studies on Locusts‘ Pathogenesis and Energy Metabolic Inhibition Induced by the Insecticidal Protein Purified from Pseudomonas Pseudoalcaligenes

The insecticidal protein produced by Pseudomonas pseudoalcaligenes is purified from the suspension of the bacterial culture. As an intact molecule, the protein acts on the foregut, midgut, hindgut, vasa Malpighii and fat body, and kills locusts. The disinsection rates of feeding and injection are 63.3% and 65.7%, respectively. After 24h to 48h, it is observed that all these tissues and cells show pathological changes in varying degrees, and so did the host cellular organs of these cells, such as cytoblast, mitochondria, endoplasmic reticulum and ribosome. Particularly, the changes of the mitochondria are much more serious than those of others. Detection of oxygen electrode shows the efficiency of oxidative phosphorylation and the ATP synthesis decreases, while the activity of mitochondrial ATPase is almost not affected. That means the energy utilization of locusts is in gear, but the shortage of the supplying of energy results in their death. This research forms the substantial basis for controlling locusts.     

Cloning and characterization of Pfl_1841, a 2-methylenebornane synthase in Pseudomonas fluorescens PfO-1

The pfl_1841 gene from Pseudomonas fluorescens PfO-1 is the only gene in any of the three sequenced genomes of the Gram-negative bacterium P. fluorescens, that is, annotated as a putative terpene synthase. The predicted Pfl_1841 protein, which harbors the two strictly conserved divalent metal binding domains found in all terpene cyclases, is closely related to several known or presumed 2-methylisoborneol synthases, with the closest match being to the MOL protein of Micromonaspora olivasterospora KY11048 that has been implicated as a 2-methylenebornane synthase. A synthetic gene encoding P. fluorescens Pfl_1841 and optimized for expression in Escherichia coli was expressed and purified as an N-terminal His₆-tagged protein. Incubation of recombinant Pfl_1841 with 2-methylgeranyl diphosphate produced 2-methylenebornane as the major product accompanied by 1-methylcamphene as well as other minor, monomethyl-homomonoterpene hydrocarbons and alcohols. The steady-state kinetic parameters for the Pfl_1841-catalyzed reaction were K_M=110±13 nM and k_cat=2.4±0.1×10⁻² s⁻¹. Attempts to identify the P. fluorescens SAM-dependent 2-methylgeranyl diphosphate synthase have so far been unsuccessful.     

两株苯酚降解菌的降解特性及对比分析

采用驯化的方法从活性污泥中筛选分离得到两株高效苯酚降解菌XTT-1,XTT-3,均能在含苯酚的培养基中生长,初步鉴定均为假单胞菌属(Pseudomonassp.).研究了两株菌降解苯酚的最适条件;XTT-3菌经48 h培养可完全降解500 mg.L-1苯酚,而XTT-1菌需要64 h;两株菌的苯酚耐受能力均不超过1000 mg.L-1苯酚;NaCl含量2.0%以上对两株菌的苯酚降解率有不同程度的抑制作用.     

产吩嗪羧酸抗生素的植物根部致金色假单胞菌的菌株多样性分析与鉴定

从新疆和北京两地的十余种经济植物中的4种植物的根部分离筛选到6株可向培养基中分泌橙黄色色素物质的根内内生菌和根表附生菌,采用BOX—PCR基因组指纹图谱扩增技术对这6株细菌的遗传多样性进行了分析,结果表明这6株细菌可以划分为3个遗传群。采用系统发育和表型分析相结合对这3个遗传群的代表菌株的分类地位进行了鉴定,结果表明3个代表菌株均为绿针假单胞菌致金色假单胞菌亚种（P$eUdomonoschlororo础如subsp．aureofaciens）。采用薄层层析对3个代表菌株的色素分泌物组成进行了分析,结果显示3个代表菌株的色素分泌物组成完全相同。进一步采用电喷雾质谱和核磁共振分析确认色素主要组分为吩嗪-1-羧酸（Phenazine-1．carboxylicAcid,PCA）,并对其抗真菌活性进行了分析。结论：植物根部产吩嗪羧酸抗生素的致金色假单胞菌在菌株水平上存在着显著的多样性,这种多样性与其地理分布的多样性和宿主植物的多样性之间存在着一定程度的对应关系,其中的3株内生细菌LJ1、GL1、TC1由于与宿主植物存在极为密切的关系而有可能作为生物活体农药直接应用于宿主植物病害的生物防治,显示了很好的应用潜力。     

A new 15N tracer method to determine N turnover and denitrification of Pseudomonas stutzeri

Although denitrification is one of the key processes of ecosystem N turnover, the understanding of the regulation of the denitrification pathway is still limited due to the lack of feasible methods for the quantification of N₂ formation. Based on the previously developed isotope pairing method, we present a new in vitro ¹⁵N tracer method for the quantification of N₂ released from denitrification by bacterial cultures. The application of the new method was enabled by replacing the background air in the sample flasks with a gas mixture of He and O₂ with an approximately 50-fold reduced N₂ background (1.7% v/v), allowing for a direct and sensitive quantification of N₂ formation with isotope-ratio mass spectrometry after ¹⁵N-labelling on the one hand, but leaving the method relatively insensitive to intrusion of ambient N₂ on the other hand. The method was tested on bacterial cultures of Pseudomonas stutzeri grown at different oxygen levels. Additionally, NO and N₂O formation were determined with a chemoluminescence analyser and a gas chromatograph, respectively. Following labelling with ¹⁵N-ammonium and ¹⁵N-nitrate, it could be shown that P. stutzeri used ammonium preferably for biomass build-up, and nitrate preferably as electron acceptor. Between 84–107% of the total available N could be recovered. Due to the high sensitivity of the new method only low levels of ¹⁵N tracer were necessary, minimising substrate-induced effects and making this method also an appropriate tool for the use on soil cores. By that it offers a new method for studying denitrification in terrestrial ecosystems.     

Konstanz summer school 2018 on isotope ecology

Abstract

Biodegradation of polychlorinated biphenyls (PCBs) in soil is considered to be very complex due to various physico-chemical factors involved. Isotope labelling technique is the best to trace fate of the xenobiotic in the environment. In this work, the uniformly ¹⁴C-labelled PCB congener 11 (3,3′-chlorobiphenyl) was chosen as a low chlorinated coplanar biphenyl which was assumed to be readily degraded by microorganisms. Pleurotus ostreatus and two Pseudomonas species, representing white rot fungi and soil bacteria were used separately or in a consortium. The amount of liberated ¹⁴CO₂ and radio-HPLC, HPLC, GC-MS, and radio-TLC analyses of extracts at the end of a two-month experiment showed that the mineralization of PCB 11 was < 0.4%, volatilization < 3.1%, and 30% of radioactivity was irreversibly bound to the soil matrix. The respective contents of all intermediate metabolites were 4.7 to 10.5 and 2.5 to 2.7% where Pseudomonas alcaligenes alone or in combination with P. putida was applied. 3-Chlorobenzoic acid was the major biodegradation product.     

不动杆菌与假单胞菌对17β-雌二醇的协同降解特性

分别用纯培养与模拟培养法考察不动杆菌LM1与假单胞菌LY1组成的复合菌对17β-雌二醇(E2)的协同降解特性.结果表明:当细胞数量比为1时,复合菌对E2的降解率分别为菌株LM1和LY1单独作用的2.2倍和2.6倍,降解过程中菌株LM1和LY1的细胞数量比趋于1;在28℃,150r/min条件下培养7d后,复合菌对初始质量浓度为1,5,10,20mg/L的E2降解率分别为99.6%,97%,93%,85%;当培养基中氯化钠添加的质量分数为3.5%时,复合菌对E2的降解率显著下降(p0.05);在25℃时复合菌对鸡粪、猪粪及土壤样品中E2的降解率分别为对照组的2.7,3.0,2.8倍.即由菌株LM1和LY1组成的复合菌可通过协同作用降解E2.     

Synthesis,characterization, density functional theory calculations,and in vitro antibacterial activity of novel transition metal complexes containing an O3-tridentate amoxicillin-based Schiff base: A silver(II) complex as alternative against Pseudomonas aeruginosa resistant to amoxicillin

Transition metal complexes containing an amoxicillin-based Schiff base (H₂L, 3 ) obtained from the condensation of amoxicillin 1 with salicylaldehyde 2 were prepared. Spectroscopic and physicochemical techniques, namely, UV–visible, Fourier-transform infrared spectroscopy, ¹H NMR, electron paramagnetic resonance, transmission electron microscopy, mass spectrometry, magnetic susceptibility, molar conductance, density functional theory (DFT) calculations, together with elemental and thermal analyses were used to characterize the synthesized complexes. Based on these studies, the general formulae [ML(H₂O)₃], where M = Mn 4 , Ni 5 , Zn 6 , and [ML(H₂O)], where M = Cu 7 , Ag 8 , were proposed for the complexes. The amoxicillin-based Schiff base ligand behaved as a dianionic O₃-tridentate chelating agent. DFT studies and magnetic and spectral data revealed octahedral geometries for Mn, Ni, and Zn atoms and distorted tetrahedral geometries for Cu(II) and Ag(II) complexes. Synthesized compounds were tested for antibacterial activity by both agar disk diffusion method and the minimum inhibitory concentration. in vitro bacterial viability revealed that complex 5 had similar antibacterial activity as 1 against Staphylococcus aureus and Staphylococcus epidermidis, whereas Pseudomonas aeruginosa, resistant to amoxicillin, was sensitive to complex 8 . The antibacterial activity of complex 8 could be attributed to its greater catalytic activity as shown by DFT calculations. Toxicity bioassay of the tested compounds showed LC₅₀ values > 1000 ppm, indicating their nontoxicity against brine shrimp nauplii (Artemia salina).