超声波对铜绿微囊藻与蛋白核小球藻生理特征及竞争生长的影响

铜绿微囊藻是常见的水华蓝藻,常常在湖泊中与蛋白核小球藻共存或竞争生长。超声波可用于藻华即时治理,能够降低藻类生理活性,影响藻类生长,还可能改变藻类种间竞争关系。为了探究超声胁迫(35 kHz,0.035 W·cm^-3)对铜绿微囊藻与蛋白核小球藻的生理特征及种间竞争的影响,本研究设置纯藻组和1:1混合组(细胞浓度比)进行试验。结果表明: 铜绿微囊藻对超声胁迫更加敏感。超声处理600 s后,铜绿微囊藻的光合活性(F_v/F_m)和酯酶活性存在显著变化,纯藻组和混合组的F_v/F_m分别降低了51.8%和64.7%。而各组中蛋白核小球藻的光合活性变化较小。同时,铜绿微囊藻释放的荧光溶解性有机物(类色氨酸、类酪氨酸、类富里酸物质)含量多于蛋白核小球藻。两种藻的细胞浓度对超声波的响应也不同,蛋白核小球藻变化较小,而铜绿微囊藻的细胞浓度出现不同程度的下降。尤其是600 s超声处理大幅降低了混合组中铜绿微囊藻的细胞浓度(-42.6%),在超声胁迫解除后的8 d内蛋白核小球藻占优势,种间关系由铜绿微囊藻单边抑制蛋白核小球藻转变为两者互相抑制。在超声处理后,铜绿微囊藻的活性能够逐渐恢复,为了提高控藻效果的持久性,建议在一周后再次进行超声处理。     

铜锈环棱螺对水华中常见藻类的抑制效应

藻类水华频发已成为全球性的水环境问题,近年来,生物控藻法因具有环境友好的特点而备受关注。本研究以我国富营养化湖泊中常见大型底栖动物铜锈环棱螺为操纵生物,通过室内培养试验,研究了其对水华水体中常见蓝藻铜绿微囊藻、绿藻普通小球藻和斜生栅藻生长及光合活性的影响,以期阐明螺-藻间相互作用关系,探究铜锈环棱螺作为生物操纵物种的可行性。结果表明: 铜锈环棱螺能在短时间内大量摄食藻细胞,其对铜绿微囊藻产毒株和不产毒株以及斜生栅藻的去除率均在12 h内达到最大值,分别为73.7%、73.2%和51.1%;其对普通小球藻的摄食强于其他藻类,至试验结束时去除率达到99.2%。产毒铜绿微囊藻产生的微囊藻毒素会在铜锈环棱螺体内累积并促发其肝脏病理学变化,进而阻碍铜锈环棱螺的摄食。试验后期各处理组藻细胞光合活性均显著低于对照组,表明铜锈环棱螺的摄食作用对藻细胞造成了损伤,抑制了其大量增殖。此外,当不产毒铜绿微囊藻与斜生栅藻混合时,铜锈环棱螺的选择摄食性导致微囊藻的优势地位被斜生栅藻所取代。因此,铜锈环棱螺可以通过摄食作用抑制藻类的光合活性并降低其生物量,从而在一定程度上抑制或减缓水华的形成。     

Synthesis and biological activity of novel 1beta-methylcarbapenems with oxyiminopyrrolidinylamide moiety

The synthesis and antibacterial activity of novel 1β-methylcarbapenems 1a–f bearing oxyiminopyrrolidinylamide moiety at C-5 position of pyrrolidine are described. Most compounds exhibited comparable antibacterial activity to meropenem against a wide range of Gram-positive and Gram-negative organisms including Pseudomonas aeruginosa isolates. Of these carbapenems, 1a showed potent and broad spectrum of antibacterial activity and similar stability to DHP-I to meropenem. Against clinical isolates of 40 Gram-negative bacterial species including MDR and ESBL-producing strains, the selected carbapenem 1a possessed excellent in vitro activity except for MDR P. aeruginosa, and was comparable in potency to meropenem.     

Development of novel antibacterial peptides that kill resistant isolates

The rapid emergence of bacterial strains that are resistant to current antibiotics requires the development of novel types of antimicrobial compounds. Proline-rich cationic antibacterial peptides such as pyrrhocoricin kill responsive bacteria by binding to the 70 kDa heat shock protein DnaK and inhibiting protein folding. We designed and synthesized multiply protected dimeric analogs of pyrrhocoricin and optimized the in vitro antibacterial efficacy assays for peptide antibiotics. Pyrrhocoricin and the designed dimers killed β-lactam, tetracycline- or aminoglycoside-resistant strains of Escherichia coli, Salmonella typhimurium, Klebsiella pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in the submicromolar or low micromolar concentration range. One of the peptides also killed Pseudomonas aeruginosa. The designed dimers showed improved stability in mammalian sera compared to the native analog. In a murine H. influenzae lung infection model, a single dose of a dimeric pyrrhocoricin analog reduced the bacteria in the bronchoalveolar lavage when delivered intranasally. The solid-phase synthesis was optimized for large-scale laboratory preparations.     

温度对外源性32P在水、铜绿微囊藻和底泥中迁移的影响

采用同位素示踪法,在实验室模拟研究不同温度下外源性无机磷酸盐在水、铜绿微囊藻(Microcystis aeruginosa)和底泥中的迁移过程.外源性³²P加入水中后,首先是一种与温度无关的快速物理化学分配,大量溶解性磷酸盐迅速进入底泥和微囊藻中.随后水中³²P的迁移主要受微囊藻生长状况的影响.温度升高有利于微囊藻的生长,并提高了微囊藻吸磷的速度.微囊藻中最大外源性磷浓度只与水环境中的初始磷浓度有关.25℃时铜绿微囊藻的生长曲线有7d的对数期,没有明显的稳定期就转入衰亡期.在25℃时,当微囊藻超积累P到一定程度后,其对数生长同细胞内含P量无关.随着时间的推移,外源性³²P不断向底泥中迁移,实验末期所有的³²P都转移到底泥中.提高温度使水中溶解性外源性磷的下降速率加快,7d后水中溶解的外源性磷浓度低于0.00716mg·L^-1.     

Critical thermal maximum and body water loss in first instar larvae of three Cetoniidae species (Coleoptera)

Critical thermal maximum (CT_max) and body water losses were measured in first instar larvae of Gnorimus nobilis, Osmoderma eremita (Trichiinae) and Cetonischema aeruginosa (Cetoniinae) when air temperature was increased gradually (0.5 °C/min) from 20 °C to the critical thermal maximum (CT_max), in dry air (near 0% R.H.).

The CT_max was significantly lower in O. eremita (45.6±0.7 °C) than in G. nobilis (48.5±0.6) and C. aeruginosa (51.4±0.9 °C).

An increase of 10 °C (30–40 °C) induced a 2-fold increase of the water loss in C. aeruginosa and O. eremita (Q₁₀=2.10±0.12 and 2.13±0.20, respectively). In the range from 40 to 45 °C to CT_max a strong increase of the water loss was observed in O. eremita and C. aeruginosa, respectively. Body water losses were significantly lower in C. aeruginosa than in O. eremita and G. nobilis over the range 20 °C—CT_max; no significant difference occurred between G. nobilis and O. eremita.     

CP6679, a new injectable cephalosporin. Part 1: synthesis and structure-activity relationships

A series of cephalosporins bearing a 5,5-fused ring system, an (imidazo[5,1-b]thiazolium-6-yl)methyl group, at the C-3 position were synthesized and evaluated for in vitro antibacterial activities. CP6679 (1s) and its analogues showed potent antibacterial activities against Gram-positive and Gram-negative bacteria, including Pseudomonas aeruginosa. They were also highly active against methicillin-resistant Staphylococcus aureus (MRSA). CP6679 (1s) showed more potent antibacterial activity than ceftazidime (CAZ) or cefpirome (CPR) against Pseudomonas aeruginosa and MRSA.     

Identification of a gene, pilF, required for type 4 fimbrial biogenesis and twitching motility in Pseudomonas aeruginosa

Many bacterial pathogens produce a class of surface structures called type 4 fimbriae. In Pseudomonas aeruginosa these fimbriae are responsible for adhesion and translocation across host epithelial surfaces. We have identified a novel gene involved in the complex process of type 4 fimbrial biogenesis. This gene, termed pilF, is located on SpeI fragment S at 30 min on the P. aeruginosa genomic map, which is the sixth region on the chromosome shown to contain a fimbrial-associated gene. The PilF protein has a predicted M_r of 22 402, and together with a highly homologous upstream ORF shares a chromosomal arrangement similar to that found in Haemophilus influenzae. A pilF mutant is blocked in the export/assembly of the fimbrial subunit PilA, and accumulates this protein in the membrane fraction. Complementation studies indicate that the cloned pilF gene is able to restore the expression of surface fimbriae, twitching motility and susceptibility to fimbrial-specific bacteriophage     

Synthesis and structure-activity relationships of cephalosporins, 2-isocephems, and 2-oxaisocephems with C-3′ or C-7 catechol or related aromatics

A series of cephalosporins, 2-isocephems, and 2-oxaisocephems with C-3′ catechol-containing (pyridinium-4-thio)methyl groups and 2-isocephems with C-7 catechol related aromatics have been prepared and evaluated for antimicrobial activity. It turns out that these compounds have highly potent activity against Gram-negative bacteria, especially resistant pathogens such as Pseudomonas aeruginosa. The most active compound of the series was (6S,7S)-7-[2-(2-aminothiazol-4-yl)-2-[(Z)-[(1,5-dihydroxy-4-pyridon-2-yl)methoxy] imino]acetamido]-3-[[[(4-methyl-5-carboxymethyl)thiazol-2-yl]thio]methyl]-8-oxo-1-aza-4-thiabicyclo [4.2.0] oct-2-ene-2-carboxylic acid which exhibited potent in vitro activity against clinically isolated P. aeruginosa and Acinetobacter baumanii which is also resistant to many anti-infectives, and good in vivo efficacy against clinically isolated P. aeruginosa.

A series of cephalosporins, 2-isocephems, and 2-oxaisocephems and C-3′ or C-7 catechol or related aromatics have been prepared and evaluated for antibacterial activity.     

滇池入湖河流大清河河口段浮游藻类格局研究

2006年7月至2007年12月对大清河3个样点的浮游藻类组成及密度、浮游叶绿素a浓度等指标进行逐月监测.共观察到浮游藻类65个分类单元,计53个属.所有样点的平均藻类密度是1.23×10⁸ ind·L^-1,最高密度为1.39×10⁹ ind·L^-1,最低密度为3.21×10⁵ ind·L^-1.铜绿微囊藻(Microcystis aeruginosa)为绝对优势种,监测期间其平均相对丰度为92.23%.随着离湖距离的增加,浮游藻类总密度、铜绿微囊藻的百分含量明显降低,而香农-威纳(Shannon-Wiener)、辛普森(Simpson 1/Dominance)多样性指数和均匀度(Evenness)则呈现升高趋势.同时,样点2、3的铜绿微囊藻百分含量与滇池的极为相似,而样点1则距离滇池较远,其铜绿微囊藻的百分含量及生物多样性指数方面均不同于样点2、3,说明滇池水的倒灌已显著影响到样点2、3的藻类组成.通过比较各样点间的群落相似性指数发现:样点1、3间的相似性指数显著低于样点1、2和样点2、3间的相似性指数.样点2、3间的相似性指数除2007年4、5及7月外,均超过60%.通过对样点1、2和3的浮游藻类群落在工程运行前后进行"非度量多维标度"(NMS)分析,发现示范工程运行后的1年内还未对大清河监测河段水生生物群落的恢复有显著作用.     

New potent antimicrobial peptides from the venom of Polistinae wasps and their analogs

Four new peptides of the mastoparan family, characterized recently in the venom of three neotropical social wasps collected in the Dominican Republic, Polistes major major, Polistes dorsalis dorsalis and Mischocyttarus phthisicus were synthesized and tested for antimicrobial potency against Bacillus subtilis, Staphylococcus aureus, Escherichia coli (E.c.) and Pseudomonas aeruginosa, and for hemolytic and mast cells degranulation activities. As these peptides posses strong antimicrobial activity (minimal inhibitory concentration (MIC) values against Bacillus subtillis and E.c. in the range of 5–40 μM), we prepared 40 of their analogs to correlate biological activities, especially antimicrobial, with the net positive charge, hydrophobicity, amphipathicity, peptide length, amino acid substitutions at different positions of the peptide chain, N-terminal acylation and C-terminal deamidation. Circular dichroism spectra of the peptides measured in the presence of trifluoroethanol or SDS showed that the peptides might adopt -helical conformation in such anisotropic environments.     

Preparation and characterization of konjac glucomannan/poly(diallydimethylammonium chloride) antibacterial blend films

A novel antibacterial film was prepared by blending konjac glucomannan (KGM) and poly(diallydimethylammonium chloride) (PDADMAC) in an aqueous system. The antibacterial activity of the films against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Saccharomyces were measured by the halo zone test and the double plate method. The films exhibited an excellent antibacterial activity against B. subtilis and S. aureus but not against E. coli, P. aeruginosa or Saccharomyces. The miscibility, morphology, thermal stability, water vapour permeability and mechanical properties of the blend films were investigated by density determination, SEM, ATR-IR, XRD, DSC, TGA, WVA and tensile tests. The results of density determination predicted that the blends of KGM and PDADMAC were miscible when the PDADMAC content was less than 70 wt%. Moreover, SEM and XRD confirmed the result. ATR-IR showed that strong intermolecular hydrogen bonds and electrostatic interactions occurred between KGM and PDADMAC in the blends. The tensile strength and the break elongation of the blends were improved largely to 106.5 MPa and 32.04% and the water vapour permeability decreased when the PDADMAC content was 20 wt%. The thermal stability of the blends was higher than pure KGM. The blends should be good antibacterial materials.     

MexAB-OprM specific efflux pump inhibitors in Pseudomonas aeruginosa. Part 6: exploration of aromatic substituents

A series of 4-oxo-4H-pyrido[1,2-a]pyrimidine derivatives, derivatized at the 2-position with aromatic substituents, were synthesized by the Suzuki cross-coupling method and evaluated for their ability to potentiate the activity of the fluoroquinolone levofloxacin (LVFX) and the anti-pseudomonas β-lactam aztreonam (AZT) in Pseudomonas aeruginosa. By incorporating hydrophilic substituents onto the aryl nucleus, we found a morpholine analogue that possessed improved solubility, retained activity in vitro, and displayed potentiation activity in vivo in a rat model of P. aeruginosa pneumonia.     

Directional Modifications of Resibufogenin by Mucor subtilissimus and Pseudomonas aeruginosa

Directional modifications of resibufogenin 1 by Mucor subtilissimus and Pseudomonas aeruginosa were carried out. The substrate was hydroxylated at C-12 by M. subtilissimus AS 3.2454, from which a major product 12-hydroxyresibufogenin 2 was obtained. Then product 2 was dehydrogenated by P. aeruginosa AS 1.860, which resulted in a new compound 12β-hydroxy-3-keto-resibufogenin 3.     

Intracellular phosphorus metabolism of Microcystis aeruginosa under various redox potential in darkness

Phosphorus metabolism of Microcystis aeruginosa was studied under gradient redox potential from 252 mV to –70 mV in darkness. The release of phosphorus occurred in all the treatments, and this process was accelerated in darkness when the redox potential was lowered. Low redox potential in darkness stimulated the accumulation of polyphosphate (PolyP) and the degradation of polyglucose. The synthesis of PolyP delayed the decrease of intracellular orthophosphate. The death of M. aeruginosa was slowered when the redox potential was low in darkness. The accumulation of PolyP under low redox potential in the dark was very important to M. aeruginosa for endurance through the unfavorable growth conditions for maintaining phosphorus concentration, energy storage, and other physiological functions. The ability to accumulate PolyP in the dark and negative redox potential may be of considerable advantage in the low-light, organically rich, and low-redox habitats.     

Phenolics and antimicrobial activity of traditional stoned table olives 'alcaparra'

In the present work, we report the determination of phenolic compounds in ‘alcaparra’ table olives by reversed-phase HPLC/DAD, and the evaluation of their extract in vitro activity against several microorganisms that may be causal agents of human intestinal and respiratory tract infections, namely Gram positive (Bacillus cereus, Bacillus subtilis, and Staphylococcus aureus), Gram negative bacteria (Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumoniae) and fungi (Candida albicans and Cryptococcus neoformans). Three flavonoidic compounds were identified and quantified: luteolin 7-O-glucoside, apigenin 7-O-glucoside, and luteolin. At low concentrations (0.05 mg/mL) ‘alcaparra’ extract revealed significant inhibition of both Gram positive and Gram negative bacteria growth, with exception of P. aeruginosa. Nevertheless, no antifungal activity was observed at the tested concentrations.     

Type-specific carbohydrate antigens of pathogenic bacteria. Part 2

This review summarises the recently elucidated structures of the carbohydrate antigens of gram-negative (Haemophilus influenzae, Neisseria meningitidis, Pseudomonas aeruginosa and Vibrio cholera) and grampositive bacteria (Streptococcus pneumoniae and Group B Streptococcus). The use of carbohydrate antigens as vaccines is discussed.     

Burkholderia genome analysis reveals new enzymes belonging to the nitrilase superfamily. The amidase of Burkholderia cepacia (hospital isolate)

Burkholderia cepacia (formerly Pseudomonas cepacia) grows in media containing acetamide or propionamide as C and N sources. Chromosomal DNA from a hospital isolate of B. cepacia served as a template in PCRs using primers designed for the amplification of the P. aeruginosa amiE gene that encodes an aliphatic amidase. Partial sequencing of the PCR products gave a translated sequence 100% identical with the amino acid sequence of P. aeruginosa amidase. A search of Burkholderia genomes detected a putative amidase in B. cepacia J2315 with high identity to the P. aeruginosa amidase and predicted that other Burkholderia species also possessed CN_hydrolases that use the same catalytic triad (Glu–Lys–Cys) as amidase. Superimposition of theoretical three-dimensional models suggested that differences in the amino acid sequences between amidases from B. cepacia (hospital isolate) and B. cepacia J2315 do not affect their three-dimensional structure.