Polyphasic detection of cyanobacteria in terrestrial biofilms

Cyanobacterial populations detected on buildings by traditional methods are mainly filamentous, whereas direct microscopy shows that they are principally coccoid morphotypes that often cannot be isolated in culture, but may grow on artificial media when the spatial biofilm relationships are maintained. The polyphasic strategy described here was to select morphologically distinct colonies from rehydrated biofilms for direct DNA amplification, allowing uncultured organisms to be sequenced and their morphology to be characterized by microscopy. DNA data banks currently contain many entries for cyanobacteria of unrecorded morphology, which does not facilitate identification, although genetic variability in a population may be assessed. The sequence homologies of the present biofilm organisms (EMBL accession numbers AJ619681 to 619690) with those in DNA databanks were low, indicating differences between xerophytic cyanobacteria on walls and aquatic species comprising the majority in the databases. Further development of databases for the populations found in this environment, subject to temperature extremes, repeated desiccation and high UV and salt levels, is required.     

甲亢患者甲状腺激素水平与血脂代谢相关性分析及临床意义探讨

目的:探讨甲亢患者甲状腺激素水平与血脂代谢指标之间的关系。方法:对160例甲亢患者治疗前后的甲状腺激素(TH)水平、血脂水平进行对照分析。结果:甲亢治疗前后与健康对照组比较,游离三碘甲状腺原氨酸(FT3)、游离甲状腺素(FT4)明显增高,促甲状腺激素(TSH)明显降低,差异有统计学意义(P<0.01);总胆固醇(TC)、三酰甘油(TG)、高密度脂蛋白胆固醇(LDL-C)、载脂蛋白A(apoAΙ)、载脂蛋白B(apoB)均明显降低,且差异具有统计学意义(P<0.01);低密度脂蛋白胆固醇(HDL-C)无明显变化(P>0.05)。结论:甲状腺激素与脂类代谢密切相关,临床上在诊治甲亢患者时,应当加强血脂水平的监测,以便更好地指导临床诊治,为疾病的发生发展、判断预后提供有价值的实验室检测指标。     

Physiological metal uptake by Nostoc punctiforme

Trace metals are required for many cellular processes. The acquisition of trace elements from the environment includes a rapid adsorption of metals to the cell surface, followed by a slower internalization. We investigated the uptake of the trace elements Co(2+), Cu(2+), Mn(2+), Ni(2+), and Zn(2+) and the non-essential divalent cation Cd(2+) in the cyanobacterium Nostoc punctiforme. For each metal, a dose response study based on cell viability showed that the highest non-toxic concentrations were: 0.5?μM Cd(2+), 2?μM Co(2+), 0.5?μM Cu(2+), 500?μM Mn(2+), 1?μM Ni(2+), and 18?μM Zn(2+). Cells exposed to these non-toxic concentrations with combinations of Zn(2+) and Cd(2+), Zn(2+) and Co(2+), Zn(2+) and Cu(2+) or Zn(2+) and Ni(2+), had reduced growth in comparison to controls. Cells exposed to metal combinations with the addition of 500?μM Mn(2+) showed similar growth compared to the untreated controls. Metal levels were measured after one and 72?h for whole cells and absorbed (EDTA-resistant) fractions and used to calculate differential uptake rates for each metal. The differences in binding and internalisation between different metals indicate different uptake processes exist for each metal. For each metal, competitive uptake experiments using (65)Zn showed that after 72?h of exposure Zn(2+) uptake was reduced by most metals particularly 0.5?μM Cd(2+), while 2?μM Co(2+) increased Zn(2+) uptake. This study demonstrates that N. punctiforme discriminates between different metals and favourably substitutes their uptake to avoid the toxic effects of particular metals.     

铜绿假单胞菌临床菌株TTSS表达水平及相关因素分析

Ⅲ型分泌系统（type Ⅲ secretion system, TTSS）是铜绿假单胞菌的重要致病因子．分析临床菌株中TTSS的表达水平,对于研究铜绿假单胞菌的致病机制具有重要意义．本研究通过测定融合报告基因exsA-lacZ和exoT-lacZ编码的β-半乳糖苷酶活力,分析了150株铜绿假单胞菌临床菌株exsA和exoT基因的表达水平,发现71株（47.33%）细菌exsA基因的表达为阳性,65株（43.33%）细菌exoT基因的表达为阳性,基因exsA与exoT表达水平存在正相关（P <0.001）,且不同菌株间两者表达水平差异较大．采用统计学方法对实验结果进一步分析发现,TTSS表达与呼吸道感染等临床症状相关（P <0.05）;与标本的分离时间相关（P =0.029）;与菌株亚胺青霉烯耐药性存在负相关（P <0.05）．本研究结果显示,铜绿假单胞菌临床菌株TTSS表达水平差异较大,与多种因素存在相关性.     

三种杜拉属（Drawida）蚯蚓的酯酶同工酶的初步研究

应用聚丙烯酰胺凝胶电泳的方法，对寡毛纲杜拉属三种蚯蚓进行酯酶同工酶酶谱分析。其结果表明，同属蚯蚓具有几条相似的酶谱区带，而不同种蚯蚓又具有各自独特的酶谱带，种间酶谱区带数目、泳动率及染色强度都有明显区别。雅和杜拉蚓酶谱图和天锡杜拉蚓相似，而与管状杜拉蚓相差较远，表明同属蚯蚓在进化水平上的亲缘关系。     

Effects of Saxitoxin (STX) and Veratridine on Bacterial Na+-K+ Fluxes: a Prokaryote-Based STX Bioassay

Saxitoxin (STX) is a potent natural sodium channel blocker and represents a significant health concern worldwide. We describe here the antagonistic effects of STX and veratridine (VTD), an Na⁺ channel activator, on three gram-negative bacteria and their application to an STX bioassay. STX reduced the total cellular levels of both Na⁺ and K⁺, as measured by flame photometry, whereas VTD increased the cellular concentrations relative to control ion fluxes in the cyanobacterium Cylindrospermopsis raciborskii AWT205. Endogenous STX production in toxic cyanobacterial strains of C. raciborskii and Anabaena circinalis prevented cell lysis induced by VTD stress. Microscopic cell counts showed that non-STX producing cyanobacteria displayed complete cell lysis and trichome fragmentation 5 to 8 h after addition of VTD and vanadate (VAN), an inhibitor of sodium pumps. The addition of STX, or its analogue neoSTX, prior to treatment with VTD plus VAN prevented complete lysis in non-STX-producing cyanobacteria. VTD also affected cyanobacterial metabolism, and the presence of exogenous STX in the sample also ameliorated this decrease in metabolic activity, as measured by the cellular conversion of tetrazolium into formazan. Reduced primary metabolism was also recorded as a decrease in the light emissions of Vibrio fischeri exposed to VTD. Addition of STX prior to VTD resulted in a rapid and dose-dependent response to the presence of the channel blocker, with samples exhibiting resistance to the VTD effect. Our findings demonstrate that STX and VTD influence bacterial Na⁺ and K⁺ fluxes in opposite ways, and these principles can be applied to the development of a prokaryote-based STX bioassay.     

Screening, identification and kinetic characterization of a bacterium for Mn(II) uptake and oxidation

Following sample collection and screening at a number of Mn-associated mine sites in Northern Australia, a microbial strain was selected for its enhanced rate of Mn uptake. The strain was identified by phylogenetic analysis as a Rhizobium sp. Kinetic studies of Mn(II) uptake and oxidation by this strain in glucose-based media established that the uptake of Mn(II) was much greater than the conversion of Mn(II) to Mn oxide. Chemical analysis and scanning electron microscopy confirmed the production of significant amounts of polysaccharides by this strain. These polysaccharides may play a role both in enhancing Mn(II) accumulation and in minimizing Mn oxide production.     

Detection of Toxigenicity by a Probe for the Microcystin Synthetase A Gene (mcyA) of the Cyanobacterial Genus Microcystis: Comparison of Toxicities with 16S rRNA and Phycocyanin Operon (Phycocyanin Intergenic Spacer) Phylogenies

The relationship between toxigenicity and phylogeny within the cyanobacterial genus Microcystis is unclear. To investigate this issue, we have designed PCR primers for the N-methyltransferase (NMT) domain of the microcystin synthetase gene mcyA and have probed 37 Microcystis sp. cultures as well as several field samples. The NMT region was present in all 18 laboratory strains that gave positive reactions in the protein phosphatase inhibition assay for microcystin but was absent in 17 nontoxic strains. Two other nontoxic strains, one of which had previously been reported to produce microcystin, possessed the NMT region. Detection of NMT-specific DNA in field samples corresponded to periods of toxicity as assessed by protein phosphatase inhibition. The Microcystis strains formed a monophyletic cluster based on 16S rRNA gene sequences but comprised two groups with respect to phycocyanin intergenic spacer (PC-IGS) sequences. Toxic and nontoxic strains appeared to be erratically distributed within the PC-IGS and 16S rRNA trees. Sequence analysis of the NMT domain revealed two coherent groups. The genomic region immediately downstream of the mcyABC cluster in all 20 NMT-positive strains contained an open reading frame of unknown function (uma1) at a conserved distance from mcyC. All nontoxic strains also contained uma1, which is not cotranscribed with mcyABC. The consistent linkage of mcyC to uma1 suggests that mcyC has not been frequently transferred into nontoxic strains via any mechanism involving insertion at random chromosomal locations. These results are discussed with respect to various mechanisms that could explain the patchy distribution of toxigenicity among the various Microcystis clades.     

血管抑素的临床应用研究进展

血管抑素是第一个被发现的肿瘤源性血管生成抑制因子,能抑制血管内细胞的增殖和迁移,从而抑制肿瘤的生长。通过一些实验方法能够检测肿瘤患者体内的血管抑素水平。血管抑素在未来的肿瘤治疗、诊断、预后判断和新生血管疾病的治疗中有着广阔的应用前景。     

北京市不同植物群落的降温增湿效应研究

在北京市植物园选取14个不同结构特征的植物群落作为研究对象,利用温湿度记录仪对其温湿度进行测定,分别研究郁闭度、平均冠幅、叶面积指数与降温增湿效应之间的相关性。结果表明,不同群落的降温增湿效果存在较大差异:碧桃(Prunus persica Batsch.var.duplex)、洋白蜡(Fraxinus pennsylvanica)、杂种鹅掌楸(Liriodendron chinense×tulipifera)、杜仲(Eucommia ulmoides)群落的降温增湿效果较好,而绦柳(Salix matsudana f.pendula)、楸树(Catalpa bungei)、毛泡桐(Paulownia tomentosa)群落的降温增湿效果相对较弱。对实验数据进行统计分析可知,郁闭度与群落降温效应呈极显著正相关,与增湿效应呈正相关但不显著;平均冠幅与群落的降温效应呈显著正相关,但与增湿效应的正相关并不显著;叶面积指数对群落的降温效应起到一定促进作用,但对增湿效应影响不大。除此之外,其他影响植物群落降温增湿效应的结构特征有待进一步探讨。