嗜热微生物

嗜热微生物任红妍（华中农业大学植保系武汉４３００７０）嗜热微生物是一类生活在高温环境中的微生物,如火山口及其周围区域、温泉、工厂高温废水排放区等。近３０年来,这一类微生物越来越广泛地引起了科学家们的重视和兴趣。特别是在水的沸点和沸点以上温度条件下能生...     

嗜热细菌解开早期生物进化谜团

为了更好地了解内含子的早期历史，科学家对细长聚球藻（增殖原理与高等生物十分相似）进行了研究，并尝试推断内含子在真核生物中的进化过程。     

高效嗜热聚磷菌的构建

以一株能聚磷但不耐热的芽孢杆菌和一株嗜热但不聚磷的嗜热菌为亲本,PEG诱导原生质体融合,筛选出2株既耐高温又能聚磷的融合菌株。对2株融合子进行传代培养,同时对未传代培养的融合子和传代培养后的融合子进行聚磷及耐热性测定,2株菌株的聚磷能力均比亲株高,其对无机磷的聚积能力分别为27.8%和5.8%,对有机磷的聚积能力分别为39.2%和56.1%,,耐热温度达55℃。该稳定的融合子具有嗜热和聚磷的双重遗传标记,可以作为研究基因重组的材料及高温生物除磷的生产菌株,对研究聚磷菌的聚磷机理和嗜热菌耐热机理,解决夏季污水处理曝气池发泡过多现象提供一定的依据。     

中等嗜热细菌浸出黄铜矿过程中pH对群落结构的影响

为了优化浸出工艺,研究了pH对浸矿过程主要微生物种群结构的影响。用中度嗜热混合菌槽浸黄铜矿精矿,在不控制pH,控制pH为2．5及控制pH为1．2时,应用PCR-RFLP（限制性酶切片段长度多态性）方法对上述浸出条件下的细菌群落动态变化进行研究。结果表明,浸出体系只有两种微生物,一种为Acidithiobacillus Caldus,一种为Leptospirillum ferriphilum。pH对群落结构有明显影响。不控制pH时,浸出开始阶段At．caldus是优势种群,占群落的96％,随着浸出的进行,L．ferriphilum增多,在浸出后期代替At．caldus成为优势菌种,占69％。控制pH时,L．ferriphilum始终占主导地位,同时发现pH为2．5时At．caldus在群落中的丰度比pH为1．2时高。     

嗜热菌群降解偶氮染料的特性及机制

【背景】印染废水的出水温度高,抑制了微生物对偶氮染料的降解,而关于嗜热菌在高温下降解偶氮染料的报道较少。【目的】富集能在高温下降解偶氮染料的嗜热微生物菌群,并研究其降解潜力和基因组特征。【方法】通过富集的方法获得嗜热微生物菌群,利用分光光度法测定其降解特性;采用全波长扫描、傅里叶变换红外吸收光谱(Fourier transform infrared spectroscopy,FTIR)和气相质谱(gas chromatography-mass spectrometer,GC-MS)分析其降解机理;采用植物毒性的方法比较偶氮染料降解前后的毒性;采用高通量测序技术分析其功能基因和群落结构。【结果】该菌群(SD1)可以在65℃降解偶氮染料,Caldibacillus、unclassified＿f＿＿Bacillaceae、Geobacillus等为优势属,在降解过程中起关键作用;菌群SD1能在较宽泛的p H (5.0-9.0)、温度(50-75℃)、染料浓度(100-500 mg/L)和盐度(1%-5%)降解酸性大红GR;偶氮还原酶和NADH-DCIP是主要的降解酶,GC-MS和FTIR结果...     

腾冲嗜热厌氧菌热休克蛋白60及其基因表达的热激动态变化分析

热休克蛋白60(HSP60)是细菌体内一种非常重要的分子伴侣,其可以协助蛋白质或肽链的正确折叠和构型,防止变性和降解。基于本实验室的早期观察,腾冲嗜热厌氧菌的HSP60是一个典型的温度相关蛋白质,在80℃的表达水平最高。为了进一步了解嗜热菌应急的分子机制,继续进行了在热激后HSP60基因表达的动态研究。将最适温度(75℃)下培养的腾冲嗜热厌氧菌迅速地转移至80℃继续培养,然后在不同的时间点上分别取样,并通过双向电泳、Western blot和Real_time PCR等方法,分析了HSP60在mRNA和蛋白质水平上的表达量的改变。试验结果表明,在80℃热处理4h内的短期应急过程中,HSP60蛋白水平一直呈上升趋势,而它的mRNA水平则表现为先升高后下降的一个非对称性的峰形变化。HSP60的mRNA和蛋白质的对温度的应答快慢程度是不同的。HSP60的mRNA水平的显著变化在1h内便可观察到,而蛋白质水平的显著改变要延迟3h左右。此外,HSP60的mRNA和蛋白质对温度的应答量变大小也是不同的。     

超嗜热羧酸酯酶的性质和应用研究

摘要 来源于超嗜热菌的超嗜热羧酸酯酶,结构上与激素敏感性脂肪酶(HSL)家族近似,属于α/β-水解酶,但是其空间结构比HSL更加紧密而有韧性,具有很强的热稳定性。性质研究表明,温度和有机溶剂对超嗜热羧酸酯酶的活性和对映选择性影响显著;其最适底物一般是对硝基苯酯,部分酯酶的基因含有GGGX基序,能够水解叔醇酯结构。由于超嗜热羧酸酯酶的独特结构和性质,其应用潜力巨大,尤其在拆分手性的外消旋酯方面独具优势。     

不同能源条件下中度嗜热嗜酸细菌多样性分析

采用黄铁矿、黄铜矿、硫酸亚铁和硫粉混合物作为主要能源物质在50°C条件下分别培养中度嗜热细菌混合物,研究其细菌多样性。提取细菌基因组总DNA,采用PCR结合限制性酶切片段多态性分析(RFLP)方法进行细菌16SrRNA基因的系统发育分析,比较不同能源条件下富集培养的混合细菌群落构成的差异。从3个培养物中共获得阳性克隆303个并进行RFLP分析,对29种不同酶切谱型的克隆插入序列进行测定和系统发育分析。大部分序列与已报道的浸矿微生物16SrRNA序列相似性较高(89.1%~99.7%),归属于硫化叶菌属的耐温氧化硫化杆菌(Sulfobacillus thermotolerans)和热氧化硫化杆菌(Sulfobacillus thermosulfidooxidans),嗜酸硫杆菌属的喜温硫杆菌(Acidithiobacillus caldus),钩端螺旋菌属的嗜铁钩端螺旋菌(Leptospirillumferriphilum)以及unculturedforest soil bacterium、uncultured proteobacterium。其中Acidithiobacillus caldus,Sulfobacillus thermotolerans,Leptospirillumferriphilum3种细菌为三类能源物质培养物中的优势细菌类群。L.ferriphilum在黄铁矿培养体系(53.8%)和硫酸亚铁和硫粉为能源的培养体系中(45.9%)中丰度最高;在以黄铜矿为能源物质的培养体系中,S.thermotolerans的比例大幅上升(70.1%)。关键词:中度嗜热细菌;生物多样性;生物浸矿;喜温硫杆菌(Acidithiobacillus caldus);耐温氧化硫化杆菌(Sulfobacillus thermotolerans);嗜铁钩端螺旋菌(Leptospirillumferriphilum)     

嗜热细菌解开早期生物进化谜团

一个长期以来备受争议的话题是：在脑部是否有一个中心时钟,或者说计时是否是大脑中不同回路的共有本领？最近科学家发现,培养皿中的脑细胞网络可以被培养成像沙漏一样精确走时的计时器,这一结果或许可以帮助人们揭示大脑追踪时间之谜。     

一株嗜热菌的分离鉴定及其苯酚降解特性

从油田地层水中分离到一株嗜热并高效降解苯酚的BF80菌株,其最适生长和降解苯酚的温度为60℃65℃。利用API50CHB/E系统和16SrDNA序列分析对菌株BF80进行了分类鉴定,该菌株的形态和生理生化特性与Geobacillusthermoglucosidasius基本相同,其16SrDNA序列与GeobacillusthermoglucosidasiusBGSCW95A1(=ATCC43742)的相似性为99·22%。在接种量为1%的条件下,该菌在20h内能完全降解3mmol/L的苯酚;在pH值5·59·0范围内能保持对苯酚良好的降解能力,并在12mmol/L苯酚的无机盐培养基中也能生长和降解苯酚,表明该菌能耐受高浓度苯酚并可用于高温含酚废水的生物处理。     

Thermophilic chitinolytic microorganisms of brown semidesert soil

In brown semidesert soil, thermophilic prokaryotic organisms identified as Streptomyces roseolilacinus and Silanimonas lenta were shown to play the main role in chitin transformation at 50°C. The phylogenetic positions of the isolated dominant chitinolytic microorganisms were determined on the basis of 16S rRNA gene sequencing. The consumption of chitin as a source of carbon and nitrogen by both the bacterium and the actinomycete was evident from considerable biomass accumulation, high emission of carbon dioxide, and presence in the medium of the chitinase exoenzyme.     

Synergic and Opposing Activities of Thermophilic RecQ-like Helicase and Topoisomerase 3 Proteins in Holliday Junction Processing and Replication Fork Stabilization

RecQ family helicases and topoisomerase 3 enzymes form evolutionary conserved complexes that play essential functions in DNA replication, recombination, and repair, and in vitro, show coordinate activities on model recombination and replication intermediates. Malfunctioning of these complexes in humans is associated with genomic instability and cancer-prone syndromes. Although both RecQ-like and topoisomerase 3 enzymes are present in archaea, only a few of them have been studied, and no information about their functional interaction is available. We tested the combined activities of the RecQ-like helicase, Hel112, and the topoisomerase 3, SsTop3, from the thermophilic archaeon Sulfolobus solfataricus. Hel112 showed coordinate DNA unwinding and annealing activities, a feature shared by eukaryotic RecQ homologs, which resulted in processing of synthetic Holliday junctions and stabilization of model replication forks. SsTop3 catalyzed DNA relaxation and annealing. When assayed in combination, SsTop3 inhibited the Hel112 helicase activity on Holliday junctions and stimulated formation and stabilization of such structures. In contrast, Hel112 did not affect the SsTop3 DNA relaxation activity. RecQ-topoisomerase 3 complexes show structural similarity with the thermophile-specific enzyme reverse gyrase, which catalyzes positive supercoiling of DNA and was suggested to play a role in genome stability at high temperature. Despite such similarity and the high temperature of reaction, the SsTop3-Hel112 complex does not induce positive supercoiling and is thus likely to play different roles. We propose that the interplay between Hel112 and SsTop3 might regulate the equilibrium between recombination and anti-recombination activities at replication forks.     

红树植物分子生态与进化研究进展

红树林是热带与亚热带海洋森林和地球湿地生态系统的重要组成部分 ,是多种海洋动物及鸟类栖息繁衍的重要场所 ,在调节全球生态平衡及维持生物多样性方面起着十分重要的作用。有关红树林的生态生物学研究 ,特别是红树林及其生物多样性变化的监测研究 ,红树林的保护与管理已成为热带亚热带海洋及湿地生态学研究的重要内容。海南岛有长达 1 5 2 8ｋｍ的海岸线 ,红树林群落的分布十分广泛。孢粉学证据说明 ,海南岛滨海地区在第三纪时即有红树林出现[1 ] 。现海南岛红树林植物种类有 1 8科 2 6属 34种 ,占中国红树植物种数的 97.1 % [2 ] 。由于…     

Thermophilic anaerobic spirochetes in New Zealand hot springs

Abstract Electron and light microscopy revealed the presence of spirochetes in New Zealand thermal springs. The spirochete population in one spring studied (Kuirau Lake) was affected by fluctuations in temperature and/or pool level. A pure culture of the strictly anaerobic bacterium revealed that it grew optimally at a temperature of 45–50°C, with no growth occurring above 60°C, and a pH of 7.0–7.5 with no growth occurring at pH 5.5 or 8.5. Growth was inhibited by chloramphenicol, penicillin, streptomycin, tetracycline and neomycin but not by d -cycloserine, novobiocin or phosphomycin at 10 μg/ml. A wide range of carbohydrates were utilized but not organic acids. Acetate was the major end product of glucose fermentation with substantial amounts of ethanol and traces of lactate being produced.     

Contrasting patterns of disparity suggest differing constraints on the evolution of trilobite cephalic structures during the Cambrian ‘explosion’

Trilobites are an abundant group of Palaeozoic marine euarthropods that appear abruptly in the fossil record c. 521 million years ago. Quantifying the development of morphological variation (or ‘disparity’) through time in fossil groups like trilobites is critical in understanding evolutionary radiations such as the Cambrian ‘explosion’. Here, I use geometric morphometrics to quantify ‘cumulative disparity’ in functionally-important structures within the trilobite cephalon across their initial radiation during Cambrian Series 2. Overall cephalic disparity increased rapidly and attained a maximum within several million years. This pattern is dominated by the cephalic outline (in particular the genal spines), reflecting rapid, convergent expansion to the extremes of morphospace in a few early families. In contrast, removing the outline and focusing on structures such as the glabella and eye ridges (associated with feeding and vision, respectively) showed a more gradual increase in disparity, closer in line with taxonomic diversity and supporting the hypothesis of a relatively accurate trilobite fossil record. These contrasting patterns suggest that disparity in different structures was constrained in different ways, with extrinsic (ecological) factors probably having the major impact on overall disparity. It also implies that patterns of disparity in isolated substructures cannot necessarily be taken individually as representative of overall morphologies.     

The Reverse Gyrase from Pyrobaculum calidifontis,a Novel Extremely Thermophilic DNA Topoisomerase Endowed with DNA Unwinding and Annealing Activities

Reverse gyrase is a DNA topoisomerase specific for hyperthermophilic bacteria and archaea. It catalyzes the peculiar ATP-dependent DNA-positive supercoiling reaction and might be involved in the physiological adaptation to high growth temperature. Reverse gyrase comprises an N-terminal ATPase and a C-terminal topoisomerase domain, which cooperate in enzyme activity, but details of its mechanism of action are still not clear. We present here a functional characterization of PcalRG, a novel reverse gyrase from the archaeon Pyrobaculum calidifontis. PcalRG is the most robust and processive reverse gyrase known to date; it is active over a wide range of conditions, including temperature, ionic strength, and ATP concentration. Moreover, it holds a strong ATP-inhibited DNA cleavage activity. Most important, PcalRG is able to induce ATP-dependent unwinding of synthetic Holliday junctions and ATP-stimulated annealing of unconstrained single-stranded oligonucleotides. Combined DNA unwinding and annealing activities are typical of certain helicases, but until now were shown for no other reverse gyrase. Our results suggest for the first time that a reverse gyrase shares not only structural but also functional features with evolutionary conserved helicase-topoisomerase complexes involved in genome stability.