12,825 research outputs found
Comparative Metagenomics of Eight Geographically Remote Terrestrial Hot Springs.
No full textHot springs are natural habitats for thermophilic Archaea and Bacteria. In this paper, we present the metagenomic analysis of eight globally distributed terrestrial hot springs from China, Iceland, Italy, Russia, and the USA with a temperature range between 61 and 92 (∘)C and pH between 1.8 and 7. A comparison of the biodiversity and community composition generally showed a decrease in biodiversity with increasing temperature and decreasing pH. Another important factor shaping microbial diversity of the studied sites was the abundance of organic substrates. Several species of the Crenarchaeal order Thermoprotei were detected, whereas no single bacterial species was found in all samples, suggesting a better adaptation of certain archaeal species to different thermophilic environments. Two hot springs show high abundance of Acidithiobacillus, supporting the idea of a true thermophilic Acidithiobacillus species that can thrive in hyperthermophilic environments. Depending on the sample, up to 58 % of sequencing reads could not be assigned to a known phylum, reinforcing the fact that a large number of microorganisms in nature, including those thriving in hot environments remain to be isolated and characterized
Glycosynthases as tools for the production of glycan analogs of natural products
No full textOligo-, polysaccharides, and glycoconjugates are a relevant part of the bioactive components of the natural products exploited in therapeutics, diagnostics, food additives, and biomaterials. Glycans are directly involved in important biological processes, such as immunostimulation, anti-inflammatory, antioxidant, and chemoprotectant actions and/or are crucial for their activity, by modulating target recognition, stability, and pharmacokinetics. On the other hand, carbohydrate extracts used for functional studies are rather heterogeneous and lack structural information because of their intrinsic complexity hampering purification and characterization. Therefore, methods for glycoside synthesis and modification are urgently needed. Recently, glycosynthases, engineered glycoside hydrolases with no hydrolytic activity that synthesize glycans in quantitative yields, were introduced. Here we will illustrate how the glycosynthases described so far might be exploited for the production of glycan analogs of natural products and their enormous potential in this field
Translational recoding in archaea
No full textTranslational recoding includes a group of events occurring during gene translation, namely stop codon readthrough, programmed ±1 frameshifting, and ribosome bypassing, which have been found in organisms from all domains of life. They serve to regulate protein expression at translational level and represent a relatively less known exception to the traditional central 'dogma' of biology that information flows as DNA→RNA→protein and that it is stored in a co-linear way between the 5'→3' of nucleic acids and N→C-terminal of polypeptides. In archaea, in which translational recoding regulates the decoding of the 21st and the 22nd amino acids selenocysteine and pyrrolysine, respectively, only one case of programmed -1 frameshifting has been reported so far and further examples, although promising, have not been confirmed yet. We here summarize the current state-of-the-art of this field that, especially in archaea, has relevant implications for the physiology of life in extreme environments and for the origin of life
Glycosynthases: new enzymes for oligosaccharide synthesis
No full textThe mutation of putative acidrbase and nucleophile of the active sites of retaining glycosyl hydrolases, together with kinetic analysis of the mutants, and stereochemical identification of products lead to useful information for the understanding of the reaction mechanism of these enzymes. This was the preliminary and fundamental step toward the preparation of new enzymatic activities called glycosynthases. Direct exploitation of this information has been possible, leading to the design of four new enzymes for oligosaccharides synthesis. The interest for these biocatalysts rises from the fact that the yield of the reaction can be increased and selectivity can be interpreted as key characteristic of the transfer reaction instead of a balance of hydrolytic and transferring pathways followed either by substrates and products. These new biocatalysts possess different specificities and are promising and useful tools in the construction of oligosaccharide molecules of great biological interest. This short review focused the attention on different glycosynthases obtained from four glycosyl hydrolases highlighting on the preparation and development of these new enzyme
Interrupted genes in extremophilic archaea: mechanisms of gene expression in early organisms
No full textExtremophilic Archaea populate biotopes previously considered inaccessible for life. This feature, and the possibility that they are the extant forms of life closest to the last common ancestor, make these organisms excellent candidates for the study of evolution on Earth and stimulate the exobiological research in planets previously considered totally inhospitable. Among the other aspects of the physiology of these organisms, the study of the molecular genetics of extremophilic Archaea can give hints on how the genetic information is transmitted and propagated in ancient forms of life. We review here the expression of interrupted genes in a recently discovered nanoarchaeon and the mechanisms of reprogrammed genetic decoding in Archaea
Recoding in archaea
No full textStandard decoding of the genetic information into polypeptides is performed by one of the most sophisticated cell machineries, the translating ribosome, which, by following the genetic code, ensures the correspondence between the mature mRNA and the protein sequence. However, the expression of a minority of genes requires programmed deviations from the standard decoding rules, globally named recoding. This includes ribosome programmed -/+1 frameshifting, ribosome hopping, and stop codon readthrough. Recoding in Archaea was unequivocally demonstrated only for the translation of the UGA stop codon into the amino acid selenocysteine. However, a new recoding event leading to the 22nd amino acid pyrrolysine and the preliminary reports on a gene regulated by programmed -1 frameshifting have been recently described in Archaea. Therefore, it appears that the study of this phenomenon in Archaea is still at its dawn and that most of the genes whose expression is regulated by recoding are still uncharacterized
A novel, efficient and sustainable strategy for the synthesis of α-glycoconjugates by combination of a α-galactosynthase and a green solvent
No full textGlycosynthases are becoming important enzymatic tools for the synthesis of oligosaccharides. Herein, we explore for the first time the synthesis of a-glycoconjugates using a a-glycosynthase in green solvents. Using this biocatalyst, b-Gal-N3 as donor, pNP-Glc and pNP-Man as acceptors, and green co-solvents we obtained high yields and excellent selectivities in the synthesis of a-glycoconjugates. In addition, reaction scale-up is feasible and co-solvent can be recovered and reused, increasing the sustainability of the reaction process. The results demonstrate that the combination of a glycosynthase and a green solvent is a promising alternative for the synthesis of glycoconjugates. The non-hydrolytic capability of this enzyme on the product obtained is a key feature that can be expanded to other glycosynthases
Remarkable ecological and physiological diversity of the hyperthermophiles populating neighboring solfataric pools revealed by metagenomic analysis
No full textThe study of the complex communities of hyperthermophiles, composed of Bacteria, Archaea, and viruses, populating volcanic sites is of interest to understand their adaptation and evolution to extreme conditions and as a rich source of biocatalysts [1, 2]. In fact, the intrinsic stability of their enzymes to common protein denaturants made them interesting tools for biotransformations in industrial applications.
In the framework of the discovery of new enzymes for biocatalysis and biotransformations, we decided to explore the diversity of the solfataric field of Pisciarelli, Agnano (Naples, Italy), by performing a metagenomic analysis of the microbial community living in two mud/water pools that, although distant only 4.0 meters, greatly differ in both temperature and pH (T=85°C and pH 5.5; T=94°C and pH 1.5, for Pool1 and Pool2, respectively). In particular, DNA from Pool1 was extracted from the mud/water suspension while Pool2 DNA was obtained from the sediment. The deep sequencing by Illumina technology and the following in-silico analysis showed that the phylum Crenarcheaota was prevalent, but with great genera variance in the two pools according to the different environmental T and pH. The analysis of the functional categories revealed that genes involved in the carbohydrate metabolism were prevalent, followed by amino acid metabolism and by membrane transporters. The detailed phylogenetic and physiological analysis of the samples will be discussed together with the possible mechanisms of selection occurred in the two extremophilic environments.
Bibliography
1. Cobucci-Ponzano B., Aurilia V., Riccio G., Henrissat B., Coutinho P.M., Strazzulli A., Padula A., Corsaro M.M., Pieretti G., Pocsfalvi G., Fiume I., Cannio R., Rossi M., and Moracci M.: J Biol Chem, 2010, 20691-20703.
2. Cobucci-Ponzano, B., Conte, F., Strazzulli, A., Capasso, C., Fiume, I., Pocsfalvi, G., Rossi, M., Moracci.: M. Biochimie, 2010, 92, 1895-907
Characterization of a beta-glycosidase from the thermoacidophilic bacterium Alicyclobacillus acidocaldarius.
No full textIn cell free extracts of the thermoacidophilic gram-positive bacterium Alicyclobacillus acidocaldarius ATCC27009, we have identified beta-gluco- and galactosidase activities showing a specific activity of 0.1 and 12 U/mg, respectively. The two enzymatic activities are associated with different polypeptides and we show here the functional cloning, the expression in Escherichia coli and the characterisation of the beta-glucosidase (Aabeta-gly). The enzyme, which is optimally active and stable at temperatures above 65 degrees C, belongs to glycoside hydrolase family 1 (GH1) and shows wide substrate specificity on different aryl-glycosides and cello-oligosaccharides with k (cat)/K (M) for 4-nitrophenyl-beta-D-glucoside and cellobiose of 2,976 and 185 s(-1)mM(-1), respectively. Interestingly, upstream to the beta-glycosidase gene, we identified a second ORF homologous to the ATPase subunit of the bacterial ABC transporters (abc1) that is co-transcribed with the beta-glycosidase gene glyB and that could be involved in the carbohydrate import. The activity of the enzyme on cello-oligosaccharides of up to five glucose units strongly indicates that the enzyme could be involved in vivo in the degradation of glucans together with endoglucanase enzymes previously described. This, together with the co-expression of the two genes, suggests a role for the glyB-abc1 cluster in A. acidocaldarius in the degradation of cellulose and hemicelluloses
The alpha-L: -fucosidase from Sulfolobus solfataricus.
No full textGlycoside hydrolases form hyperthermophilic archaea are interesting model systems for the study of catalysis at high temperatures and, at the moment, their detailed enzymological characterization is the only approach to define their role in vivo. Family 29 of glycoside hydrolases classification groups alpha-L-fucosidases involved in a variety of biological events in Bacteria and Eukarya. In Archaea the first alpha-L-fucosidase was identified in Sulfolobus solfataricus as interrupted gene expressed by programmed -1 frameshifting. In this review, we describe the identification of the catalytic residues of the archaeal enzyme, by means of the chemical rescue strategy. The intrinsic stability of the hyperthermophilic enzyme allowed the use of this method, which resulted of general applicability for beta and alpha glycoside hydrolases. In addition, the presence in the active site of the archaeal enzyme of a triad of catalytic residues is a rather uncommon feature among the glycoside hydrolases and suggested that in family 29 slightly different catalytic machineries coexist
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