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...     

微生物嗜盐酶的研究进展

嗜盐酶一般来自于嗜盐菌,它的主要特点是严格依赖体系中一定的盐离子浓度,可以在高盐环境中维持其结构稳定,并且能够抵抗高温、p H和有机溶剂存在下的变性,因此在高盐、水/有机和非水介质环境的催化中具有重要的应用价值。本综述从盐对嗜盐酶活性和稳定性的影响、金属离子和有机溶剂对嗜盐酶的影响几个方面介绍了嗜盐酶的特点。在总结蛋白质数据库(PDB)中已有嗜盐酶的结构和特点的基础上,对嗜盐酶的嗜盐机制进行了分析,认为嗜盐酶不同于非嗜盐酶的特点在于盐桥和氢键明显增多,含有一些特殊的盐离子结合位点并且常以低聚体的形式存在,表面酸性氨基酸含量明显增多。最后对嗜盐酶的分子改造和应用进行了简要的介绍。     

嗜热酶的特性及其应用

海洋微生物作为一类生长在特殊极端环境下的生物正日益引起人们的重视。其中嗜热微生物由于能在高温温泉及火山口附近的高热环境下生长而引起人们的极大关注[1] 。同时 ,人们也从许多人工高热环境 (如堆肥 )中分离得到这种嗜热菌。近年来 ,人们从这些嗜热菌中已分离得到多种嗜热酶 (5 5℃～80℃ )及超级嗜热酶 (80℃～ 1 1 3℃ ) [2 ] 。嗜热酶不仅具有化学催化剂无法比拟的优点 ,如催化效率高和底物专一性强 ,而且酶在高温条件下的稳定性极好[3 ] 。因而它可以克服中温酶 (2 0℃～ 5 5℃ )及低温酶 (-2℃～ 2 0℃ )在应用过程中常常出现的…     

微生物几丁质酶的研究进展、应用及展望

几丁质普遍存在于地球的陆地和水生生态系统中,是地球上产量最丰富的有机大分子多聚物之一。几丁质酶在自然界中分布广泛,不仅有重要的生态意义,而且在生物技术方面应用广阔。介绍了几丁质的降解过程和几丁质酶的分类,着重阐明了几丁质酶在细菌、真菌、古菌中的分布,总结了近年来微生物几丁质酶的研究进展及其在环境废弃物管理、农业和医药等关键领域的应用,最后基于粤港澳大湾区丰富的海洋几丁质资源,对微生物几丁质酶在新兴海洋生物技术产业中的发展和贡献进行了展望。     

嗜热微生物及在高温生物冶金过程中的应用

嗜热微生物包括中度嗜热微生物和极端嗜热微生物,主要栖息于热泉、火山口、海底热液喷口、高温反应器以及工厂高温废水排放区等自然或人为产生的高温环境中。它们可以生活在40-80°C、甚至更高的温度中,其中有些具备嗜酸性及特殊的代谢类型,在高温生物冶金过程中具有应用潜力。高温生物冶金较传统中温生物冶金更具优势,其能浸出某些难处理矿、解决浸矿过程的钝化问题,以及提高浸出效率等,目前已引起了生物冶金工业的重视。本文概述了应用于生物冶金的主要嗜热微生物的生理特点、耐热机制以及对铁、铜和砷等离子的耐受机制,进一步介绍了嗜热微生物在高温生物冶金中的发展及应用。     

嗜热链霉菌过氧化氢酶的纯化及性质研究

嗜热链霉菌(Thermostreptostreptomyces sp.)T485的除去菌体的培养液,经硫酸铵盐析,Sepha- dex G—100、DEAE—Sephadex A-50及羟基磷灰石等柱层析,得到了凝胶电泳均-的过氧化氧酶,纯化了954倍,得率为7％。用浓度梯度PAGE测定分子量为152000,SDS—PAGE测定亚基分子量为57000,凝胶薄层等电点聚焦测定等电点为4．25。过氧化氢酶的反应最适温度为60℃,最适pH为7．0;对H2O2的K为50 mmol·L-1,Vmas值为6．0 mmol·min-1·mg-1。Nall3和Hg2+对酶活力有强烈抑制作用．Ca2+对酶活力有激活作用。测定了波长200—500nm的吸收光谱,在405nm处有明显的吸收峰。根据受NaN3,抑制和吸收光谱性质,推测它为含血红素酶。此外还测定了过氧化氢酶的氨基酸组成。     

嗜热酶的结构特征与热稳定性

相对于嗜温酶,嗜热酶作为生物催化剂有许多优势而受到人们的广泛重视。嗜热酶的热稳定性机制历来是生物化学家们研究的重点。本文综述了嗜热酶的结构特征及其与热稳定性的关系。相对于嗜温酶,嗜热酶的结构比较僵硬,折叠紧密,廿螺旋更长,构象张力低,大多数为多聚体。了解嗜热酶的结构特征与热稳定性的关系,对于采用酶工程改造嗜温酶从而提高其热稳定性具有重要的指导意义。     

嗜热蓝细菌高温适应机制及生物技术应用

嗜热蓝细菌是一类具有独特耐热特征的蓝细菌,可以作为研究光合生物高温适应机制的模式生物。系统解析嗜热蓝细菌的高温适应机制,有助于深入理解光合生物及其他微生物响应和适应高温环境的分子机理,同时还具有指导耐热作物培育和构建微生物耐热细胞工厂的潜在应用前景。本文全面综述了嗜热蓝细菌的相关研究进展,包括其生态分布、形态特征、组学研究和耐热机制挖掘等多个方面;此外,还对嗜热蓝细菌在生物技术领域的应用前景与未来研究方向进行了展望。本文为深入了解蓝细菌光合生理与代谢特点,特别是嗜热蓝细菌在高温适应机制方面的研究提供了参考。     

嗜冷酶及其工业应用

生物圈中超过 80 %的地方温度低于5℃ ,在生态学上低温环境的影响范围更广。生活在这些低温环境中的嗜冷菌对低温有特殊的适应性。相对于嗜温菌而言 ,嗜冷微生物在低温条件下调节其膜流动性和膜通透性的能力更强 ,含有更多的不饱和脂肪酸和短链脂肪酸 ,还可通过合成冷激蛋白来响应冷激作用。嗜冷菌也可通过基因调控和自身的抗生素作用来适应低温。近来有研究报道 ,南北极严寒地区的海洋鱼类依靠血液中的抗冻蛋白来适应低温。生物体内的大多数生化反应都是由酶催化而成的 ,所以考虑嗜冷微生物的适应机制时首先应研究嗜冷酶的适冷机制。1 .嗜…     

极端嗜酸微生物

一般认为,极端嗜酸微生物指那些生长ｐＨ上限为３．０最适生长ｐＨ在１．０～２．５之间的微生物。它们一般分布于金属硫矿床酸性矿水、生物滤沥堆、煤矿床酸性矿水以及合硫温泉和土壤中,包括原核和真核两大类。其中原核嗜酸微生物依生长的温度范围不同又可划分成常温型、中温型和高温型３个类群。由于嗜酸微生物在低品位矿生物滤沥及煤的脱硫等方面有重要应用前景,因此受到广泛重视。１极端嗜酸微生物的多样性及主要类群在极端酸性环境中的真核生命几乎完全限于微生物。在黄石公园的温泉水体中已分离到光合作用的藻类。从其它一些地方金…     

高温菌生物学特性的应用

高温菌是一个热点研究领域。这一领域不断发现新的苗种及特性。高温菌广泛地存在于自然界中,它与常温菌相比有着许多不同的特性。例如,其酶在高温下的稳定性,为化工应用提供了便利。简要介绍了高温微生物已有的应用领域,为进一步的研究工作提供参考。     

A Comparative Molecular Dynamics Study of Thermophilic and Mesophilic Ribonuclease HI Enzymes

Abstract

We studied a pair of homologous thermophilic and mesophilic ribonuclease HI enzymes by molecular dynamics simulations. Each protein was subjected to three 5 ns simulations in explicit water at both 310 K and 340 K. The thermophilic enzyme showed larger overall positional fluctuations at both temperatures, while only the mesophilic enzyme at the higher temperature showed significant instability. When the temperature is changed, the relative flexibility of different local segments on the two proteins changed differently. Principal component analysis showed that the simulations of the two proteins explored largely overlapping regions in the conformational space. However, at 340 K, the collective structure variations of the thermophilic protein are different from those of the mesophilic protein. Our results, although not in accordance with the view that hyperthermostability of proteins may originate from their conformational rigidity, are consistent with several recent experimental and simulation studies which showed that thermophilic proteins may be conformationally more flexible than their mesophilic counterparts. The decorrelation between conformational rigidity and hyperthermostability may be attributed to the temperature dependence and long range nature of electrostatic interactions that play more important roles in the structural stability of thermophilic proteins.     

Identification of Thermophilic Bacterial Strains Producing Thermotolerant Hydrolytic Enzymes from Manure Compost

Ten thermophilic bacterial strains were isolated from manure compost. Phylogenetic analysis based on 16S rRNA genes and biochemical characterization allowed identification of four different species belonging to four genera: Geobacillus thermodenitrificans, Bacillus smithii, Ureibacillus suwonensis and Aneurinibacillus thermoaerophilus. PCR-RFLP profiles of the 16S-ITS-23S rRNA region allowed us to distinguish two subgroups among the G. thermodenitrificans isolates. Isolates were screened for thermotolerant hydrolytic activities (60–65°C). Thermotolerant lipolytic activities were detected for G. thermodenitrificans, A. thermoaerophilus and B. smithii. Thermotolerant protease, α-amylase and xylanase activities were also observed in the G. thermodenitrificans group. These species represent a source of potential novel thermostable enzymes for industrial applications.     

Thermophilic denitrifying bacteria: A survey of hot springs in Southwestern Iceland

Abstract Samples of water, sediment and bacterial mat from hot springs in Grændalur and Hveragerdi areas in southwestern Iceland were screened at 70°C and 80°C for thermophilic denitrifying bacteria by culturing in anaerobic media containing nitrate or N₂O as the terminal oxidant. The s springs ranged in temperature from 65–100°C and included both neutral (pH 7–8.5) and acidic (pH 2.5–4) types. Nitrate reducing bacteria (nitrate → nitrite) and denitrifiers (nitrate → N₂) were found that grew at 70°C but not at 80°C in nutrient media at pH 8. Samples from neutral springs that were cultured at pH 8 failed to yield a chemolithotrophic, sulfur-oxidizing and nitrate-reducing bacterium, and samples from acidic springs that were cultured at pH 3.5 seemed entirely to lack dissimilatory, nitrate-utilizing bacteria. No sample yielded an organism capable of growth solely by N₂O respiration. The denitrifiers appeared to be Bacillus . Two such Bacillus strains were examined in pure culture and found to exhibit the unusual denitrification phenotype described previously for the mesophile, Pseudomonas aeruginosa , and one other strain of thermophilic Bacillus . The phenotype is characterized by the ability to grow by reduction of nitrate to N₂ with N₂O as an intermediate but a virtual inability to reduce N₂O when N₂O was the sole oxidant.     

Thermophilic bacterial leaching of manganese dioxide

Summary Thermophilic bacterial leaching of low-grade manganese oxide ore was, demonstrated at 50°C and 70°C. A static culture system was used with cane molasses as the nutrient source. By employing batch cultures, with an acid wash to redissolve adsorbed Mn²⁺ at completion of each batch, the bacterial reduction could be driven to completion.     

嗜热真菌的分离鉴定与系统发育分析

目的:研究广西热带地区嗜热真菌的多样性.方法:从广西热带地区各地采集的土壤样品,将土样撒在PDA平板上,50℃高温培养,挑取真菌菌丝进一步划线分离纯化,20℃低温培养验证获得嗜热真菌,对其进行形态观察和ITS基因序列分析.结果:共分离到33株嗜热真菌,形态和分子生物学鉴定结果显示分离到的菌株中有20株属于Thermomyces lanuginosus,4株属于Thermoascus aurantiacus,1株属于Chaetomium thermophilum,l株属于Talaromyces emersonii,1株属于Myceliophthora thermophila,还有6株的ITS序列与已知真菌的同源性很低,尚无法鉴定到种属.结论:广西热带地区的嗜热真菌存在多样性,Thermomyces lanuginosus为该地区主要嗜热真菌种.     

Thermophilic methane production and oxidation in compost

Methane cycling within compost heaps has not yet been investigated in detail. We show that thermophilic methane oxidation occurred after a lag phase of up to one day in 4-week old, 8-week old and mature (>10-week old) compost material. The potential rate of methane oxidation was between 2.6 and 4.1 micromol CH4(gdw)(-1)h(-1). Profiles of methane concentrations within heaps of different ages indicated that 46-98% of the methane produced was oxidised by methanotrophic bacteria. The population size of thermophilic methanotrophs was estimated at 10(9) cells (gdw)(-1), based on methane oxidation rates. A methanotroph (strain KTM-1) was isolated from the highest positive step of a serial dilution series. This strain belonged to the genus Methylocaldum, which contains thermotolerant and thermophilic methanotrophs. The closest relative organism on the basis of 16S rRNA gene sequence identity was M. szegediense (>99%), a species originally isolated from hot springs. The temperature optimum (45-55 degrees C) for methane oxidation within the compost material was identical to that of strain KTM-1, suggesting that this strain was well adapted to the conditions in the compost material. The temperatures measured in the upper layer (0-40 cm) of the compost heaps were also in this range, so we assume that these organisms are capable of effectively reducing the potential methane emissions from compost.     

一株产高温蛋白酶嗜热菌A-2的筛选鉴定及酶学特性分析

本研究为从云南腾冲热泉中分离纯化得到一株产高温蛋白酶的菌株并对其进行驯化培养,用以探究该菌株的生长条件及酶学特性,通过选择培养基筛选能够分解脱脂奶粉产蛋白酶的菌株,应用常规方法液体培养菌体,探究温度、pH、碳源、氮源对菌株生长情况的影响,并采用福林酚法测蛋白酶活性。并提取蛋白酶液对酶的最适pH、温度以及热稳定性、pH稳定性进行研究。结果发现通过含脱脂奶粉的固体培养基筛选得到一株产蛋白酶菌株A-2,经过生理生化试验和16S rDNA鉴定知该菌种属于Aneurinibacillus属。酵母粉、葡萄糖、55℃、pH值7.5分别为菌株生长的最适氮源、碳源、温度和pH。此外该菌株所产的蛋白酶最适温度为60℃,在pH值7~9具有较好的酶活性。因此,该菌株为嗜热芽孢杆菌,所产的碱性蛋白酶具有较高的耐受温度和pH稳定性,为进一步开发利用提供参考的价值。     

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.     

RNA干扰机制及其应用研究进展

2006年诺贝尔生理学或医学奖,授予给了美国科学家Andrew Z.Fire和Craig C.Mello以表彰他们发现了RNA 干扰(RNAinterference RNAi)现象,使人们在基因治疗传染性、恶性肿瘤等危重疾病领域取得了突破性的发展.本文主要综述了RNA干扰系统的组成、分子机制、作用特点及其在探索基因功能、传染性、恶性肿瘤的基因治疗和药物研发等四个方面的应用.