中度嗜盐或耐盐放线菌生长对阴离子选择性研究*

长期以来Cl^-被作为主要阴离子来分离和培养中度嗜盐放线菌,但是盐湖中还含有NO3^-、SO4^2-、CO3^2-和HCO3^-等阴离子。培养基中只加入含有Cl^-的盐,不能完全模拟出自然界的环境,因此对中度嗜盐或耐盐放线菌的研究会有一定的限制。实验通过研究部分中度嗜盐或耐盐放线菌菌株生长对阴离子的选择影响,结果发现中度嗜盐或耐盐放线菌对部分阴离子如NO3^-和SO4^2-没有太大的选择性,Cl^-可以被NO3^-和SO4^2-所代替;但有些阴离子如CO3^2-和HCO3^-仅对拟诺卡氏菌属(Nocardiopsis)影响较小,对盐碱环境中的其他属的放线菌,如普氏菌属(Prauserella)、链单孢菌属(Streptomonospora)、糖单孢菌属(Saccharomonospora)等影响较大。     

中度嗜盐菌相容性溶质机制的研究进展

生活在高盐环境中的中度嗜盐菌不仅能抗衡外界的高渗透压胁迫,而且还能迅速适应短时间内的渗透冲击。为适应该环境,中度嗜盐菌依赖于一种被称为相容性溶质的物质,以执行渗透保护功能。这类物质属于极性的、易溶的和低分子量的有机化合物,其中包括糖类、氨基酸类、甜菜碱类和四氢嘧啶类等。中度嗜盐菌主要采用相容性溶质机制来适应盐环境。在此,就中度嗜盐菌的盐适应机理、相容性溶质的种类和特点,以及其作用的分子机制进行了阐述和讨论。     

极端嗜盐菌的特性及其应用前景

主要介绍极端嗜盐菌的嗜盐机理、细菌视紫红质(bR)和嗜盐菌素的研究进展,然后对其在环境生物治理、生物电子和医药工业等领域的应用研究进行总结和展望。     

嗜盐微生物

高盐环境通常是指那些盐浓度高于海水的环境．在这些环境中能够生存的微生物可划分为三类：一“类是能耐受一定浓度的盐溶液,但在无盐存在条件下生长最好的菌称为耐盐菌．第二类是一定浓度的盐为菌体生长所必需,且在一定浓度的盐溶液中生长最好,称为嗜盐菌．在盐浓度从零至饱和的盐溶液中均能生长,在一定浓度的盐溶液中生长最好的特殊类群称为多能盐生苗。依据嗜盐浓度的不同,嗜盐菌又可分为轻度嗜盐菌（最适盐浓度0．2—0．smol／L）、中度嗜盐菌（最适盐浓度0．5—2．omol／L）和极端嗜盐菌（最适盐浓度＞3mol／U,其中部分极端嗜…     

中度嗜盐菌产木聚糖酶发酵条件的研究

中度嗜盐菌在盐碱环境下生长繁殖,其产生的木聚糖酶也同样具有在盐碱环境下发挥作用的特性。本文对一株中度嗜盐菌的产木聚糖酶活性进行了初步研究。研究包括氮源、液体种子接种量、培养温度、pH值、培养时间等因素对该菌株产木聚糖酶能力的影响。结果表明,最佳培养氮源为蛋白胨;最佳产生木聚糖酶的发酵条件是液体种子接种量为6%,温度为35℃,pH值7,培养时间为4 d。     

嗜盐古菌分类学研究进展

嗜盐古菌是一类需要高盐维持生长的古菌。到目前为止,已发现的嗜盐古菌都属于古菌域的广古菌门,主要包括:嗜盐甲烷古菌类群、嗜盐古菌纲的全部成员以及尚不能培养的纳米嗜盐古菌类群。嗜盐古菌是盐环境的土著类群,驱动着盐环境生态系统的生物地球化学循环。作为极端微生物,嗜盐古菌在理论研究和应用领域具有重要的研究价值。本文从嗜盐古菌分类学地位的变迁、分类学方法、分类学研究现状及我国的嗜盐古菌分类学研究等方面综述了嗜盐古菌分类学的最新研究进展。     

青藏高原察尔汗盐湖地区可培养中度嗜盐菌的群落结构与多样性

【目的】研究青海察尔汗盐湖地区的可培养中度嗜盐菌的群落结构及多样性。【方法】采用多种选择性培养基进行中度嗜盐菌的分离、培养;通过16S r RNA基因序列扩增、测定,根据序列信息,进行系统进化树构建、群落结构组成分析及多样性指数计算。【结果】从察尔汗盐湖卤水及湖泥中分离到中度嗜盐菌421株,合并重复菌株后共83株中度嗜盐菌。菌株16S rRNA基因序列信息显示,4株中度嗜盐菌为潜在的新分类单元。83株嗜盐细菌分布于3个门的6个科16个属。其中,Bacillus属、Oceanobacillus属和Halomonas属为优势属。多样性结果显示,水样中的菌株多样性高于泥样,而泥样中的菌株优势度高于水样。【结论】察尔汗盐湖中度嗜盐菌具有丰富的遗传多样性,种群种类丰富,优势菌群集中,该盐湖地区存在可分离培养的中度嗜盐菌的疑似新物种。     

新疆艾丁湖中度嗜盐苯酚降解菌多样性研究

高盐含酚废水属于极难处理的废水之一,筛选具有生物学降解能力的嗜盐菌有助于解决这一难题。从新疆艾丁湖盐湖中分离筛选能够降解苯酚的中度嗜盐菌,了解盐湖中度嗜盐苯酚降解菌的多样性组成和降解能力。研究结果表明,10%(质量分数)的盐浓度条件下,分离得到166株嗜盐菌,通过以苯酚为唯一碳源的培养基进行降解活性筛选后得到45株阳性菌,根据细菌16S rRNA基因序列系统进化分析,这45株菌分别归类到3个门,5个科,9个属。其中拟诺卡氏菌属(Nocardiopsis)是优势菌,占总量的68.8%,其余菌分布于Bacillus、Gracilibacillus、Pontibacillus、Halobacillus、Marinococcus和Halomonas属。在含100 mg/L苯酚的液体培养基,经过10 d培养后,这45株菌降解效率为1%~17%。本研究为工业应用提供了嗜盐微生物种质资源,极具进一步发掘和研究价值。     

新疆达坂城盐湖中度嗜盐微生物的筛选分离与其抑菌性、生长特性初步研究

极端微生物作为非常宝贵的微生物资源,具有广阔的研究和应用前景。为获得中度嗜盐微生物,采用渗透压选择性培养基,从采自新疆达坂城盐湖及附近的20份水土样本中获得6株中度嗜盐菌,其中包括2株细菌、1株放线菌和3株霉菌。其中两株嗜盐菌对包括大肠杆菌在内的三种指示菌有不同程度的抑制作用。对有抑菌能力的两株中度嗜盐微生物进行生长特性的初步研究,发现其最适生长盐度为10%(以NaCl计),当盐度超过15%时则不生长;在pH6~9,温度25~37℃条件下均长势良好。     

酸微菌纲(Acidimicrobiia)的研究概况

酸微菌是酸微菌纲(Acidimicrobiia)下所有菌的统称,广泛存在于酸性矿废水和海洋、湖泊、土壤、沙漠等环境,因其难培养、特殊的生理特性而受到特别的关注。酸微菌在酸性、中性和弱碱性环境中均有分布,一部分种属嗜酸、中度嗜热、可进行Fe2+氧化和Fe3+还原反应,具有矿石氧化和合成新型活性物质的能力,在生物浸矿与化学合成有潜在的应用价值;一部分种属存在于中性或弱碱性的土壤、沙漠和水体中,是该类环境中放线菌的优势种类。本文概述了酸微菌纲的建立和发展、酸微菌的系统发育、生物多样性与地理分布、主要生理特性、代谢途径、基因组研究等情况,并对酸微菌的应用前景和未来研究方向进行展望。     

Potential of halotolerant and halophilic microorganisms for biotechnology

Halotolerant or halophilic microorganisms, able to live in saline environments, offer a multitude of actual or potential applications in various fields of biotechnology. The technical applications of bacteriorhodopsin comprise holography, spatial light modulators, optical computing, and optical memories. Compatible solutes are useful as stabilizers of biomolecules and whole cells, salt antagonists, or stress-protective agents. Biopolymers, such as biosurfactants and exopolysaccharides, are of interest for microbially enhanced oil recovery. Other useful biosubstances are enzymes, such as new isomerases and hydrolases, that are active and stable at high salt contents. Halotolerant microorganisms play an essential role in food biotechnology for the production of fermented food and food supplements. The degradation or transformation of a range of organic pollutants and the production of alternative energy are other fields of applications of these groups of extremophiles.     

Mining metagenomes for novel cellulase genes

Cellulases hydrolyze the β-1,4 linkages of cellulose and are widely used in food, brewing and wine, animal feed, textiles and laundry, and pulp and paper industries, especially for hydrolyzing cellulosic materials into sugars, which can be fermented to produce useful products such as ethanol. Metagenomics has become an alternative approach to conventional culture-dependent methods as it allows exhaustive mining of microbial genomes in their natural environments. This review covers the current state of research and challenges in mining novel cellulase genes from the metagenomes of various environments, and discusses the potential biotechnological applications of metagenome-derived cellulases.     

Alkaliphiles — from an industrial point of view

Abstract: Organisms with pH optima for growth in excess of pH 9 are defined as alkaliphiles (or sometimes alkalophiles). Alkaliphiles contain prokaryotes, eukaryotes, and archaea. It is clear that many different taxa are represented among the alkaliphiles, and some of them are proposed as new taxa. Alkaliphiles can b isolated from normal environments such as garden soil, although counts of the alkaliphiles are higher in alkaline environments. Alkaliphiles have made a great impact in industrial applications. Biological detergents contain alkaline enzymes, such as alkaline cellulases and/or alkaline proteases that have been produced from alkaliphiles. The current proportion of total world enzyme production destined for the laundry detergents market exceeds 30%. Another important application is the industrial production of cyclodextrin with alkaline cyclomaltodextrin glucanotransferase. This enzyme reduced the production cost and paved the way for its use in large quantities in foodstuffs, chemicals and pharmaceuticals. Besides these applications, there are other possible applications in food and waste treatment industries.     

Identification of Listeria monocytogenes genes involved in salt and alkaline-pH tolerance

The capacity of Listeria monocytogenes to tolerate salt and alkaline stresses is of particular importance, as this pathogen is often exposed to such environments during food processing and food preservation. We screened a library of Tn917-lacZ insertional mutants in order to identify genes involved in salt and/or alkaline tolerance. We isolated six mutants sensitive to salt stress and 12 mutants sensitive to salt and alkaline stresses. The position of the insertion of the transposon was located in 15 of these mutants. In six mutants the transposon was inserted in intergenic regions, and in nine mutants it was inserted in genes. Most of the genes have unknown functions, but sequence comparisons indicated that they encode putative transporters.     

Biology of Moderately Halophilic Aerobic Bacteria

The moderately halophilic heterotrophic aerobic bacteria form a diverse group of microorganisms. The property of halophilism is widespread within the bacterial domain. Bacterial halophiles are abundant in environments such as salt lakes, saline soils, and salted food products. Most species keep their intracellular ionic concentrations at low levels while synthesizing or accumulating organic solutes to provide osmotic equilibrium of the cytoplasm with the surrounding medium. Complex mechanisms of adjustment of the intracellular environments and the properties of the cytoplasmic membrane enable rapid adaptation to changes in the salt concentration of the environment. Approaches to the study of genetic processes have recently been developed for several moderate halophiles, opening the way toward an understanding of haloadaptation at the molecular level. The new information obtained is also expected to contribute to the development of novel biotechnological uses for these organisms.     

Halophilic anaerobic fermentative bacteria

In hypersaline environments bacteria are exposed to a high osmotic pressure caused by the surrounding high salt concentrations. Halophilic microorganisms have specific strategies for balancing the osmotic pressure and surviving in these extreme conditions. Halophilic fermentative bacteria form taxonomically and phylogenetically a coherent group mainly belonging to the order Halanaerobiales. In this review, halophilic anaerobic fermentative bacteria in terms of taxonomy and phylogeny, special characteristics, survival strategies, and potential for biotechnological applications in a wide variety of branches, such as production of hydrogen, are discussed.     

Identification of Listeria monocytogenes Genes Involved in Salt and Alkaline-pH Tolerance

The capacity of Listeria monocytogenes to tolerate salt and alkaline stresses is of particular importance, as this pathogen is often exposed to such environments during food processing and food preservation. We screened a library of Tn917-lacZ insertional mutants in order to identify genes involved in salt and/or alkaline tolerance. We isolated six mutants sensitive to salt stress and 12 mutants sensitive to salt and alkaline stresses. The position of the insertion of the transposon was located in 15 of these mutants. In six mutants the transposon was inserted in intergenic regions, and in nine mutants it was inserted in genes. Most of the genes have unknown functions, but sequence comparisons indicated that they encode putative transporters.     

Salt stress proteins induced in Listeria monocytogenes

The ability of Listeria monocytogenes to tolerate salt stress is of particular importance, as this pathogen is often exposed to such environments during both food processing and food preservation. In order to understand the survival mechanisms of L. monocytogenes, an initial approach using two-dimensional polyacrylamide gel electrophoresis was performed to analyze the pattern of protein synthesis in response to salt stress. Of 400 to 500 visible proteins, the synthesis of 40 proteins (P < 0.05) was repressed or induced at a higher rate during salt stress. Some of the proteins were identified on the basis of mass spectrometry or N-terminal sequence analysis and database searching. Twelve proteins showing high induction after salt stress were similar to general stress proteins (Ctc and DnaK), transporters (GbuA and mannose-specific phosphotransferase system enzyme IIAB), and general metabolism proteins (alanine dehydrogenase, CcpA, CysK, EF-Tu, Gap, GuaB, PdhA, and PdhD).     

The ecology and taxonomy of aerobic chemoorganotrophic halophilic eubacteria

Abstract There exists a wide diversity of halophilic eubacteria with chemoorganotrophic-aerobic metabolism. Most of them have a more moderate salt response than halophilic archaebacteria, falling into the category of moderately halophilic bacteria. Although mostly isolated from salted food, their natural habitats are hypersaline waters of intermediate levels of salt concentration, and hypersaline soils. In hypersaline waters, the taxonomic groups found are the ones that also predominate in ocean waters, such as representatives of the genera Vibrio, Pseudomonas and Flavobacterium . However, in hypersaline soils, the taxonomic groups present are those typical of normal soils, such as Pseudomonas, Bacillus and Gram-positive cocci. The halophilic bacteria from soils are also more resistant to exposure to low salt concentrations than the organisms isolated from waters. Therefore, it seems that the general characteristics of the hypersaline environments drastically affect the types of halophilic bacteria present, and that the halophilic character has arisen in many phylogenetic groups of eubacteria.     

Haloarchaea: worth exploring for their biotechnological potential

Halophilic archaea are unique microorganisms adapted to survive under high salt conditions and biomolecules produced by them may possess unusual properties. Haloarchaeal metabolites are stable at high salt and temperature conditions that are useful for industrial applications. Proteins and enzymes of this group of archaea are functional under salt concentrations at which bacterial counterparts fail to be active. Such properties makes haloarchaeal enzymes suitable for salt-based applications and their use under dehydrating conditions. For example, bacteriorhodopsin or the purple membrane protein present in halophilic archaea has the most recognizable applications in photoelectric devices, artificial retinas, holograms etc. Haloarchaea are also useful for bioremediation of polluted hypersaline areas. Polyhydroxyalkanoates and exopolysccharides produced by these microorganisms are biodegradable and have the potential to replace commercial non-degradable plastics and polymers. Moreover, halophilic archaea have excellent potential to be used as drug delivery systems and for nanobiotechnology by virtue of their gas vesicles and S-layer glycoproteins. Despite of possible applications of halophilic archaea, laboratory-to-industrial transition of these potential candidates is yet to be established.