极端微生物及其应用研究进展

极端微生物是指在高/低温、高/低p H、高盐、高压等极端环境条件下生存的微生物.特殊的生存条件导致其具有特殊的遗传背景和代谢途径,并可产生功能特殊的酶类和活性物质.随着系统生物学和合成生物学技术的发展,极端微生物作为一类特殊的微生物群体,在生物医疗、生物能源和生物材料等领域具有巨大的应用潜力.极端微生物相关研究也对生命起源与演化、生物工程技术等领域的发展具有重大意义.本文对极端环境及极端微生物的概念和分类进行了回顾,综述了极端微生物在不同环境条件下的适应机制及其酶的应用,并介绍了合成生物学在极端微生物研究中的应用情况.此外,由于极端微生物和极端酶的特殊性和高效性,本文还探讨了极端微生物开发过程中的挑战,以及其在航空航天与国防安全领域的综合应用潜力,并指出了相关研究的必要性.     

可用于二氧化碳捕获过程的微生物碳酸酐酶的挖掘与改造

二氧化碳排放量的急剧上升引起全球温室效应加剧。碳酸酐酶是地球上反应速率最快的几种酶之一,可以大幅提高CO_2捕获和生物矿化的效率,从而降低大气中CO_2的排放量。但捕获过程在高温条件,而CO_2生物矿化形成CaCO_3的过程则需要碱性条件。因此,迫切需要筛选出既嗜热又耐碱的碳酸酐酶以用于CO_2捕获,极端微生物是这类酶的重要来源之一。文中系统、深入地介绍了目前从极端微生物或利用蛋白质工程技术获取嗜热、耐碱的碳酸酐酶的最新研究进展,同时简要介绍了一些新型固定化碳酸酐酶的方法。最后指出当前研究的重点应致力于拓宽寻找碳酸酐酶的范围,改良蛋白质工程改造技术,研发高效廉价、易于放大的固定化方法,为减轻温室效应、延缓全球变暖这一迫切需要解决的问题提供新思路。     

深海微生物资源研究开发技术进展

深海微生物由于生存环境的特殊性而具有各种与陆地和浅海微生物不同的功能,这些特殊功能具有重要的应用价值,是争夺激烈的深海热点资源之一。近年来,不断有新的研究技术和方法得到应用,推动了深海微生物资源的获取、研究和开发。对深海微生物菌株和基因资源研究开发方面的技术发展以及工作策略进行了综述与讨论。     

嗜极微生物的多样性

嗜极微生物(extremophilicmicrobes)指的是极端条件下生存及繁衍的微生物,也称极端环境微生物。这个微生物世界的成员,有的能培养,从中获得培养物;有的则否,但它是客观存在的,通过间接的方法推断其存在。这些年来,人们较为熟悉的嗜极微生物有嗜碱微生物、嗜酸微生物、嗜高温微生物、嗜冷微生物、嗜盐微生物、嗜高压微生物;还有把抗辐射微生物、耐干旱微生物列为嗜极微生物。这充分表明,嗜极微生物生存于地球、宇宙间的多样性。就那些嗜盐微生物而言,也有它的多样性,丰富多彩。在美国,研究人员发现结晶盐中存在着微生物世界,也就是说,在大块…     

地球熔岩管道微生物研究对天体生物学的启示

天体生物学作为与深空探测相结合的交叉学科,旨在从地球极端环境类比、古代生命载体信息发掘和模拟等方面揭示地外行星体是否适合生命生存和繁衍,其中适宜的环境条件是评价所有天体是否宜居的重要条件。近年来在月球和火星等行星表面发现了大量由火山熔岩流形成的熔岩管道,这些巨型管状地下空间具有稳定的温度和防辐射等环境条件,为生物在地外星体上的生存提供了潜在的庇护场所。基于地球熔岩管道的天体生物学的类比研究可以为探索地外生命痕迹提供重要线索,本文综述了现阶段地球熔岩管道内微生物的研究进展、微生物痕量气体代谢在天体生物学研究中的潜力及天体生物学的研究进展,旨在为后续开展地球及地外熔岩管道的天体生物学研究提供思路。     

嗜热微生物酶的嗜热机制及应用研究进展

从细胞膜组分、蛋白质结构、遗传物质、钨元素等方面阐述了嗜热微生物酶的嗜热机制 ,并简要介绍了其应用的研究进展。     

古老的嗜极微生物

在极端环境条件下生存的微生物又有古微生物之称,主要是古菌,所谓“古”,即有些细菌几千万年来一直生活在地球表面下层几万公里的深处,它们生活在没有阳光的黑暗深处,靠什么来维持其生存呢？研究人员（LIN Li-Hung）极其同事在南非一个金矿钻到2．8km深处的一个水层中对其有水、有矿的地方进行采样,发现一类靠分解硫酸盐化合物获得能源以维持生存的细菌。     

极端微生物：一种新型的酶资源

极端微生物具有自身独特的特点和代谢产物 ,在食品工业、化工、药用工业和环境生物技术领域都有潜在的应用。一些酶已经得到纯化 ,其基因在宿主中已成功克隆。主要介绍和讨论极端微生物的类型、基因组及极端酶类的生产、分离与应用。     

深海冷泉微生物遗传资源研究进展

深海冷泉由甲烷等烃类化合物渗漏形成,其独特的生态环境孕育了新颖且系统发育多样的原核生物、真核生物和病毒。冷泉微生物通过化能合成作用获得能量和物质,驱动碳、硫、氮等元素的生物地球化学循环,维持着冷泉生态系统的稳定。冷泉生境蕴含丰富的微生物遗传资源,特别是极端环境下产生的酶和次级代谢产物,具有脱卤、固氮和抗菌等作用,在农业、药物开发和环境保护等领域展现出潜在的应用前景。此外,冷泉微生物与天然气水合物开采的环境影响评估紧密相关,并在全球气候变化中扮演重要角色。为了有效开发深海冷泉微生物的遗传资源,未来研究应通过原位采样、测序和培养技术,结合环境参数监测,深入探讨冷泉微生物的生态角色与进化机制,挖掘冷泉微生物的基因资源,研究水合物开采中的微生物响应,从而为全面开发深海冷泉微生物遗传资源及水合物资源提供科学依据。     

极端嗜热性微生物纤维素酶的活性

极端嗜热厌氧菌H173羧甲基纤维素酶的最适pH为6.5-7.0.加入二硫苏糖醇(DTT)和CaCl_2.2H_2O能使酶活稳定.80℃酶活非常稳定,放置120分钟仍保留原酶活的77%,90℃9分钟保留50%的活性,120分钟仅保留3%的原始酶活.在缓冲溶液中该酶能将微晶纤维素水解成葡萄糖和纤维二糖.培养基中含有最高至50mm葡萄糖时,对溶解微晶纤维素的活性不敏感.HPLC分析表明葡萄糖是该酶在液体培养基中的主要水解终产物.     

Adaptive radiation of chemosymbiotic deep-sea mussels

Adaptive radiations present fascinating opportunities for studying the evolutionary process. Most cases come from isolated lakes or islands, where unoccupied ecological space is filled through novel adaptations. Here, we describe an unusual example of an adaptive radiation: symbiotic mussels that colonized island-like chemosynthetic environments such as hydrothermal vents, cold seeps and sunken organic substrates on the vast deep-sea floor. Our time-calibrated molecular phylogeny suggests that the group originated and acquired sulfur-oxidizing symbionts in the Late Cretaceous, possibly while inhabiting organic substrates and long before its major radiation in the Middle Eocene to Early Oligocene. The first appearance of intracellular and methanotrophic symbionts was detected only after this major radiation. Thus, contrary to expectations, the major radiation may have not been triggered by the evolution of novel types of symbioses. We hypothesize that environmental factors, such as increased habitat availability and/or increased dispersal capabilities, sparked the radiation. Intracellular and methanotrophic symbionts were acquired in several independent lineages and marked the onset of a second wave of diversification at vents and seeps. Changes in habitat type resulted in adaptive trends in shell lengths (related to the availability of space and energy, and physiological trade-offs) and in the successive colonization of greater water depths.     

Lateral symbiont acquisition in a maternally transmitted chemosynthetic clam endosymbiosis

Deep-sea clams of the family Vesicomyidae live in symbiosis with intracellular chemosynthetic bacteria. These symbionts are transmitted maternally (vertically) between host generations and should therefore show a pattern of genetic variation paralleling that of the cotransmitted host mitochondrion. However, instances of lateral (nonvertical) symbiont acquisition could still occur, thereby decoupling symbiont and mitochondrial phylogenies. Here, we provide the first evidence against strict maternal cotransmission of symbiont and mitochondrial genomes in vesicomyids. Analysis of Vesicomya sp. mt-II clams from hydrothermal vents on the Juan de Fuca Ridge (northeastern Pacific) revealed a symbiont phylotype (designated symB(VII)) highly divergent from previously described symbionts of the same host lineage. SymB(VII)-hosting clams occurred at low frequency (0.02) relative to individuals hosting the dominant symbiont phylotype. Phylogenetic analysis of 16S rRNA genes from a wide range of symbionts and free-living bacteria clustered symB(VII) within the monophyletic clade of vesicomyid symbionts. Further analysis of 3 symbiont loci (23S, dnaK, and soxA) across 11 vesicomyid taxa unambiguously placed symB(VII) as sister to the symbiont of a distantly related host lineage, Vesicomya sp. from the Mid-Atlantic Ridge (98.9% median nucleotide identity across protein-coding loci). Using likelihood and Bayesian model discrimination methods, we rejected the strict maternal cotransmission hypothesis by showing a significant decoupling of symbiont and host mitochondrial (COI and mt16S genes) phylogenies. Indeed, decoupling occurred even when symB(VII) was excluded from phylogenetic reconstructions, suggesting a history of host switching in this group. Together, the data indicate a history of lateral symbiont transfer in vesicomyids, with symB(VII) being the most conspicuous example. Interpreted alongside previous studies of the vesicomyid symbiosis, these results suggest a mixed mode of symbiont transmission characterized by predominantly vertical transmission punctuated with instances of lateral symbiont acquisition. Lateral acquisition may facilitate the exchange of genetic material (recombination) among divergent symbiont lineages, rendering the evolutionary history of vesicomyid symbiont genomes much more complex than previously thought.     

深海热液区超嗜热古菌Thermococcus sp. TVG2的培养分离与鉴定

【目的】培养分离大西洋脊热液区的超嗜热古菌,为进一步认识该生态系统中的物种及其特点奠定基础。【方法】将大西洋脊热液区海水样品用YTSV培养基富集培养,选取其中富集效果最佳的TVG2培养物用减绝稀释法分离纯化。对所分离菌株进行形态、生理生化特征等分析,并通过分子生物学手段对其进行初步鉴定。【结果】菌株TVG2属于超嗜热厌氧球菌,直径约1.0 μm;生长温度范围50?88 °C,最适生长温度82 °C;生长pH范围为5.0?9.0,最适生长pH 6.5;生长NaCl浓度为1.0%?4.0% (质量体积比),最适生长浓度为2.5%;元素硫可显著提高菌株TVG2的生物量,但非生长必需;丙酮酸钠能显著促进该菌株生长,但葡萄糖对其生长则有抑制作用。根据其形态特征、生理生化特性及16S rRNA基因序列分析,确定菌株TVG2属于热球菌属。【结论】用YTSV培养基从大西洋脊热液区样品中分离获得超嗜热厌氧菌株TVG2,并确定其为Thermococcus属成员,命名为Thermococcus sp. TVG2。     

南海F-冷泉和冲绳海槽热液区可培养二甲基巯基丙酸内盐合成与降解细菌的分离鉴定及其多样性

【目的】 冷泉和热液是海洋中典型的化能生态系统,其独特的理化特征孕育了特殊的微生物类群。二甲基巯基丙酸内盐(dimethylsulfoniopropionate, DMSP)是地球上最丰富的有机硫化合物之一,多种海洋细菌能够合成与降解DMSP,在驱动海洋碳、硫元素循环过程中发挥重要作用。本研究对南海F-冷泉和冲绳海槽热液区的DMSP合成与降解细菌进行了分离鉴定,分析其多样性与分布,拓展了对海洋中DMSP代谢细菌的认识。【方法】 选取南海F-冷泉和冲绳海槽Yaeyama Knoll热液区不同深度水体、沉积物和动物为研究对象,利用3种富集培养基(甲硫氨酸添加、高盐低氮条件用于富集DMSP合成细菌,DMSP添加用于富集DMSP降解细菌)和2216E分离培养基进行细菌的富集与分离培养。通过16S rRNA基因测序确定菌株分类地位,并检测代表菌株的DMSP合成与降解能力。【结果】 本研究共获得874株可培养细菌,其中γ-变形菌纲(Gammaproteobacteria)为3种培养基中获得的优势纲;海杆菌属(Marinobacter)为优势属。经富集后冷泉样品的可培养菌株数量和多样性均高于热液样品。冷泉来源的14株DMSP合成细菌分属于7个属,其中5株属于近海螺旋菌属(Thalassospira)且含有DMSP合成基因mmtN,2株属于假栖大洋菌属(Pseudooceanicola)并含有dsyB。冷泉来源的130株DMSP降解细菌分属于39个属,谷氨酸杆菌属(Glutamicibacter)为最优势属(24株)且不含已知DMSP降解基因。热液区来源的DMSP合成细菌仅1株,降解细菌18株,均远少于冷泉样品。具有DMSP裂解途径的菌株占降解细菌总数(148株)的98.6%,其中55株裂解活性较强且以放线菌纲(Actinobacteria)为主。在40株不同种且DMSP降解能力较强的菌株中,9株含有已知的裂解基因,3株含有已知的脱甲基基因。【结论】 南海F-冷泉和冲绳海槽热液区存在丰富的DMSP合成与降解细菌,包括多种含有潜在新型DMSP合成/降解基因的细菌类群。本研究为进一步深入理解化能生态系统中微生物驱动的有机硫循环提供了基础。     

A Review on the Phylogeography of Potentially Chemoautotrophic Bacteria from Major Vent and Seep Fauna and Their Contribution to Primary Production

Though geochemically and microbially well-defined, the phylogeographic data of microbial symbionts in these highly productive vent and seep systems require a closer examination and synthesis. QIIME analysis of 16S rDNA of bacterial associates of major fauna from 1995 to 2015 was thus undertaken to examine phylogeography of their microbial symbionts along with host specificity. While phylotypes were generally unrelated, bivalve Calyptogena exhibited vertical transmission sharing similar symbionts in geographically separated geosystems. Different species of tubeworms possessed identical symbionts through horizontal acquisition at geographically distinct Guaymas basin vent and the Arctic seep. Vents were more versatile with both mobile and sessile fauna hosting ecto- and endo-symbionts. Comparatively, seeps were more specialized with sessile animal hosts with endosymbionts. C-fixation rate measurements are still scanty for sediments, bedrocks and serpentine systems; vent, seep, anoxic and oxic basins were shown to fix up to 22, 325, 96, and 37,400 g C m^?3 y^?1, respectively. Estimation of chemosynthetic primary production rates in chemoautotrophic ecosystems could endeavor to improve existing biogeographic models by coupling volcanism and plate-tectonics to global climate and phylogeography.     

Halomonas profundus sp. nov., a new PHA-producing bacterium isolated from a deep-sea hydrothermal vent shrimp

Aims:  The objective of the present work was to describe a new deep-sea, aerobic, mesophilic and heterotrophic bacterium, referenced as strain AT1214, able to produce polyhydroxyalkanoates (PHAs) under laboratory conditions. This bacterium was isolated from a shrimp collected nearby a hydrothermal vent located on the Mid-Atlantic Ridge. Methods and Results:  This micro-organism, on the basis of the phenotypical features and genotypic investigations, can be clearly assigned to the Halomonas genus and the name of Halomonas profundus is proposed. Optimal growth occurred between 32 and 37°C at a pH between 8 and 9 and at ionic strength between 20 and 30 g l⁻¹ of sea salts. The G + C content of DNA was 58·6%. This bacterium produced PHAs of poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) from different carbon sources. Conclusions:  The bacterium H. profundus produces PHA of 3HB and 3HV monomers from different carbon sources. Significance and Impact of the Study:  PHAs share physical and material properties that suggest them for application in various areas, and are considered as an alternative to nonbiodegradable plastics produced from fossil oils. In this study, we describe a new bacteria isolated from a deep-sea hydrothermal vent with the capability to produce polyesters of biotechnological interest.