Sponge-Associated Microorganisms: Evolution, Ecology, and Biotechnological Potential

Summary: Marine sponges often contain diverse and abundant microbial communities, including bacteria, archaea, microalgae, and fungi. In some cases, these microbial associates comprise as much as 40% of the sponge volume and can contribute significantly to host metabolism (e.g., via photosynthesis or nitrogen fixation). We review in detail the diversity of microbes associated with sponges, including extensive 16S rRNA-based phylogenetic analyses which support the previously suggested existence of a sponge-specific microbiota. These analyses provide a suitable vantage point from which to consider the potential evolutionary and ecological ramifications of these widespread, sponge-specific microorganisms. Subsequently, we examine the ecology of sponge-microbe associations, including the establishment and maintenance of these sometimes intimate partnerships, the varied nature of the interactions (ranging from mutualism to host-pathogen relationships), and the broad-scale patterns of symbiont distribution. The ecological and evolutionary importance of sponge-microbe associations is mirrored by their enormous biotechnological potential: marine sponges are among the animal kingdom's most prolific producers of bioactive metabolites, and in at least some cases, the compounds are of microbial rather than sponge origin. We review the status of this important field, outlining the various approaches (e.g., cultivation, cell separation, and metagenomics) which have been employed to access the chemical wealth of sponge-microbe associations.     

Acetogens: Biochemistry,Bioenergetics, Genetics,and Biotechnological Potential

Microbiology - The review discusses the present-day data on the biochemistry, bioenergetics, and genetics of acetogens, as well as their biotechnological potential. Acetogens are anaerobic...     

微生物在生物能源生产中的应用(英文)

生物可再生能源是最有前景的石油替代品之一.生物能源的生产原料包括:植物、有机废弃物和微生物.微生物在生物能源生产上有着广泛的应用,利用微生物制备的主要生物能源包括:生物柴油、生物乙醇、生物甲烷等.某些微生物如微藻和真菌可以生产大量油脂,这些油脂可以转化为生物柴油;有些微生物如酵母可以将糖类、淀粉以及纤维素转化为燃料乙醇,添加乙醇的汽油或柴油燃烧排放明显降低;还有些厌氧微生物可以将有机废弃物转化为甲烷,可用做家用燃气、车用燃气或发电.除此之外微生物还具有在生产能源的同时治理环境污染的优势.总之研究开发微生物在生物能源生产中的应用有利于世界可持续发展.     

Genetics of Ethanol-Producing Microorganisms

Abstract

Ethanol-Producing Microrganisms

A wide variety of microbial species are known to produce ethanol as a product of carbohydrate fermentation.¹ Organisms which have received attention in recent studies include a wide range of yeasts, some molds, and a number of specialized bacteria (Table 1). Traditionally, yeasts, particularly Saccharomyces cerevisiae, have been used for producing fermentation ethanol or alcoholic beverages in large-scale processes. In Table 1, Zymomonas mobilis, the predominant organism in fermentations producing Mexican “pulque” or palm wine,³⁴-⁴⁶ is the only bacterium of current economic significance. However, the development of interest in other species with the ability, for example, to convert xylose to ethanol or to ferment at high temperatures indicates that no existing strain of Saccharomyces or Zymomonas meets the specifications for all current and future uses. Certainly the use of alternative organisms, or even mixed cultures,⁴²⁴⁵ warrants investigation. However, this review will concentrate on proven ethanol producers (i.e., yeasts, particularly Saccharomyces spp., and Z. mobilis) and how these might be improved in a systematic way for ethanol production, using the wide range of genetic techniques which is now available.     

The Biotechnological Potential of Thraustochytrids

Thraustochytrids are common marine microheterotrophs, taxonomically aligned with heterokont algae. Recent studies have shown that some thraustochytrid strains can be cultured to produce high biomass, containing substantial amounts of lipid rich in polyunsaturated fatty acid (PUFA). It is also evident that cell yield and PUFA production by some thraustochytrid strains can be varied by manipulation of physical and chemical parameters of the culture. At present, fish oils and cultured phototrophic microalgae are the main commercial sources of PUFA. The possible decline of commercial fish stocks and the relatively complex technology required to commercially produce microalgae have prompted research into possible alternative sources of PUFA. The culture of thraustochytrids and other PUFA-producing microheterotrophs is seen as one such alternative. Indeed, several thraustochytrid-based products are already on the market, and research into further applications is continuing. Many fish and microalgal oils currently available have relatively complex PUFA profiles, increasing the cost of preparation of high-purity PUFA oils. In contrast, some of the thraustochytrids examined to date have simpler PUFA profiles. If these or other strains can be grown in sufficient quantities and at an appropriate cost, the use of thraustochytrid-derived oils may decrease the high expense currently involved with producing high-purity microbial oils. As more is learned about the health and nutritional benefits of PUFA, demand for PUFA-rich products is expected to increase. Results to date suggest that thraustochytrids could form an important part in the supply of such products. Received February 17, 1999; accepted June 25, 1999     

Pyrrhotite Biooxidation by Moderately Thermophilic Acidophilic Microorganisms

Microbiology - The goal of the present work was to study the oxidation of sulfide mineral pyrrhotite by members of microbial groups predominant in biohydrometallurgical processes (mixotrophic iron-...     

天然类胡萝卜素生物合成与生物技术应用

类胡萝卜素是重要天然食用色素族群之一,它不仅可为食品添色,还具有较高营养保健价值。类胡萝卜素广泛存在于高等植物、藻类、少数微生物和部分动物体内,但不同生物在合成途径细节及所积累的类胡萝卜素种类方面存在较大的差异。通过优化培养条件、转基因和水解酶辅助提取等生物技术手段提高了类胡萝卜素产量,降低了生产成本,从而使天然类胡萝卜素制品得到更广泛的应用。     

Isolation and Characterization of Extremely Thermophilic Bacteria from Hot Springs

In order to investigate the mechanism of microbial growth at elevated temperatures, it was tried to isolate different thermophilic microorganisms from wide origins, such as soils, composts, manure piles and hot spring waters. As the result, 5 strains of extremely thermophilic bacteria, the maximum, the optimum and the minimum temperatures for growth of which were 80, 70~75, and 40°C, respectively, were isolated from Izu-Atagawa hot spring and Beppu hot springs. These bacteria were gram-negative, yellow-pigmented, non-motile and non-sporulating rods of 0.5~0.7 μ in diameter and 2~5 μ in length. They were heterotrophs requiring several amino acids (such as glutamate, aspartate, et al.) and vitamins (such as biotin, folic acid and p-aminobenzoic acid) and grew well at neutral to slight alkali pH. The content of GC pairs of DNAs from the 5 strains was 69~70%, and this seemed to be one of the highest values in bacteria so far known. Among the 5 strains, strain AT–62 was named as Thermus flavus sp. n. AT–62 from its morphological and physiological characteristics. Comparison between Thermus flavus and other extremely thermophilic bacteria as Thermus aquaticus and Flavobacterium thermophilum is described and discussed in reference to classification of extremely thermophilic bacteria.     

Growth and Reproduction of Microorganisms Under Extremely Alkaline Conditions

An aerobic and an anaerobic strain of bacteria were isolated from two extremely alkaline springs. Growth and reproduction of both microorganisms were demonstrated above pH 11.0.     

Bioleaching of Enargite and Tennantite by Moderately Thermophilic Acidophilic Microorganisms

Microbiology - The goal of the present work was to study the bioleaching of chalcopyrite (CuFeS2), enargite (Cu3AsS4), and tennantite (Cu12As4S13) by pure and mixed cultures of moderately...     

A Novel Malate Dehydrogenase from Ceratonia siliqua L. Seeds with Potential Biotechnological Applications

A novel malate dehydrogenase (MDH; EC 3.1.1.1.37), hereafter MDHCs, from Ceratonia siliqua seeds, commonly known as Carob tree, was purified by using ammonium sulphate precipitation, ion exchange chromatography on SteamLine SP and gel-filtration. The molecular mass of the native protein, obtained by analytical gel-filtration, was about 65?kDa, whereas, by using SDS-PAGE analysis, with and without reducing agent, was 34?kDa. The specific activity of purified MDHCs (0.25?mg/100?g seeds) was estimated to be 188 U/mg. The optimum activity of the enzyme is at pH 8.5, showing a decrease in the presence of Ca²⁺, Mg²⁺ and NaCl. The N-terminal sequence of the first 20 amino acids of MDHCs revealed 95?% identity with malate dehydrogenase from Medicago sativa L. Finally, the enzymatic activity of MDHCs was preserved even after absorption onto a PVDF membrane. To our knowledge, this is the first contribution to the characterization of an enzyme from Carob tree sources.     

Nanotechnology and Potential of Microorganisms

ABSTRACT

There is a growing need to develop clean, nontoxic and environmentally friendly (“green chemistry”) procedures for synthesis and assembly of nanoparticles. The use of biological organisms in this area is rapidly gaining importance due to its growing success and ease of formation of nanoparticles. Presently, the potential of bio-organisms ranges from simple prokaryotic bacterial cells to eukaryotic fungus and even live plants. In this article we have reviewed some of these biological systems, which have revolutionized the art of nano-material synthesis.     

Biotechnological Applications of Acetic Acid Bacteria

The acetic acid bacteria (AAB) have important roles in food and beverage production, as well as in the bioproduction of industrial chemicals. In recent years, there have been major advances in understanding their taxonomy, molecular biology, and physiology, and in methods for their isolation and identification. AAB are obligate aerobes that oxidize sugars, sugar alcohols, and ethanol with the production of acetic acid as the major end product. This special type of metabolism differentiates them from all other bacteria. Recently, the AAB taxonomy has been strongly rearranged as new techniques using 16S rRNA sequence analysis have been introduced. Currently, the AAB are classified in ten genera in the family Acetobacteriaceae. AAB can not only play a positive role in the production of selected foods and beverages, but they can also spoil other foods and beverages. AAB occur in sugar- and alcohol-enriched environments. The difficulty of cultivation of AAB on semisolid media in the past resulted in poor knowledge of the species present in industrial processes. The first step of acetic acid production is the conversion of ethanol from a carbohydrate carried out by yeasts, and the second step is the oxidation of ethanol to acetic acid carried out by AAB. Vinegar is traditionally the product of acetous fermentation of natural alcoholic substrates. Depending on the substrate, vinegars can be classified as fruit, starch, or spirit substrate vinegars. Although a variety of bacteria can produce acetic acid, mostly members of Acetobacter, Gluconacetobacter, and Gluconobacter are used commercially. Industrial vinegar manufacturing processes fall into three main categories: slow processes, quick processes, and submerged processes. AAB also play an important role in cocoa production, which represents a significant means of income for some countries. Microbial cellulose, produced by AAB, possesses some excellent physical properties and has potential for many applications. Other products of biotransformations by AAB or their enzymes include 2-keto-L-gulonic acid, which is used for the production of vitamin C; D-tagatose, which is used as a bulking agent in food and a noncalorific sweetener; and shikimate, which is a key intermediate for a large number of antibiotics. Recently, for the first time, a pathogenic acetic acid bacterium was described, representing the newest and tenth genus of AAB.     

Sulfur Reduction by the Extremely Thermophilic Archaebacterium Pyrodictium occultum

The relationship between growth and biological sulfur reduction for the extremely thermophilic archaebacterium Pyrodictium occultum was studied over a temperature range of 98 to 105°C. The addition of yeast extract (0.2 g/liter) to the medium was found to increase hydrogen sulfide production significantly, especially at higher temperatures. Sulfide production in uninoculated controls with and without yeast extract was noticeable but substantially below the levels observed in samples containing the microorganism.