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- Appeltans, W., et al.
(författare)
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The Magnitude of Global Marine Species Diversity
- 2012
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822 .- 1879-0445. ; 22:23, s. 2189-2202
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Tidskriftsartikel (refereegranskat)abstract
- Background: The question of how many marine species exist is important because it provides a metric for how much we do and do not know about life in the oceans. We have compiled the first register of the marine species of the world and used this baseline to estimate how many more species, partitioned among all major eukaryotic groups, may be discovered. Results: There are similar to 226,000 eukaryotic marine species described. More species were described in the past decade (similar to 20,000) than in any previous one. The number of authors describing new species has been increasing at a faster rate than the number of new species described in the past six decades. We report that there are similar to 170,000 synonyms, that 58,000-72,000 species are collected but not yet described, and that 482,000-741,000 more species have yet to be sampled. Molecular methods may add tens of thousands of cryptic species. Thus, there may be 0.7-1.0 million marine species. Past rates of description of new species indicate there may be 0.5 +/- 0.2 million marine species. On average 37% (median 31%) of species in over 100 recent field studies around the world might be new to science. Conclusions: Currently, between one-third and two-thirds of marine species may be undescribed, and previous estimates of there being well over one million marine species appear highly unlikely. More species than ever before are being described annually by an increasing number of authors. If the current trend continues, most species will be discovered this century.
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| 2. |
- Arnling Bååth, Jenny, 1987, et al.
(författare)
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Biochemical and structural features of diverse bacterial glucuronoyl esterases facilitating recalcitrant biomass conversion
- 2018
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Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834 .- 1754-6834. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Background Lignocellulose is highly recalcitrant to enzymatic deconstruction, where the recalcitrance primarily results from chemical linkages between lignin and carbohydrates. Glucuronoyl esterases (GEs) from carbohydrate esterase family 15 (CE15) have been suggested to play key roles in reducing lignocellulose recalcitrance by cleaving covalent ester bonds found between lignin and glucuronoxylan. However, only a limited number of GEs have been biochemically characterized and structurally determined to date, limiting our understanding of these enzymes and their potential exploration. Results Ten CE15 enzymes from three bacterial species, sharing as little as 20% sequence identity, were characterized on a range of model substrates; two protein structures were solved, and insights into their regulation and biological roles were gained through gene expression analysis and enzymatic assays on complex biomass. Several enzymes with higher catalytic efficiencies on a wider range of model substrates than previously characterized fungal GEs were identified. Similarities and differences regarding substrate specificity between the investigated GEs were observed and putatively linked to their positioning in the CE15 phylogenetic tree. The bacterial GEs were able to utilize substrates lacking 4-OH methyl substitutions, known to be important for fungal enzymes. In addition, certain bacterial GEs were able to efficiently cleave esters of galacturonate, a functionality not previously described within the family. The two solved structures revealed similar overall folds to known structures, but also indicated active site regions allowing for more promiscuous substrate specificities. The gene expression analysis demonstrated that bacterial GE-encoding genes were differentially expressed as response to different carbon sources. Further, improved enzymatic saccharification of milled corn cob by a commercial lignocellulolytic enzyme cocktail when supplemented with GEs showcased their synergistic potential with other enzyme types on native biomass. Conclusions Bacterial GEs exhibit much larger diversity than fungal counterparts. In this study, we significantly expanded the existing knowledge on CE15 with the in-depth characterization of ten bacterial GEs broadly spanning the phylogenetic tree, and also presented two novel enzyme structures. Variations in transcriptional responses of CE15-encoding genes under different growth conditions suggest nonredundant functions for enzymes found in species with multiple CE15 genes and further illuminate the importance of GEs in native lignin–carbohydrate disassembly.
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| 5. |
- Mazurkewich, Scott, 1982, et al.
(författare)
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Biochemical and structural investigation of the CE15 family: Glucuronoyl esterases acting on recalcitrant biomass
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Glucuronoyl esterases (GEs) are a relatively new class of enzymes which cleave ester linkages between lignin and glucuronoxylan. GEs have been identified in many biomass-degrading microbes and are now classified into the Carbohydrate Esterase Family 15 (CE15). The CE15 family is diverse (as low as 20% sequence identity), however to-date only a few GEs from a small clade of the CE15 phylogenetic tree have been biochemically characterized and only two protein structures have been solved. To investigate the diversity of CE15 members, we have studied a broad range of proteins from across the phylogenetic tree. Enzymes were biochemically characterized and three-dimensional structures for two of the enzymes were solved. Analysis of the structures suggest possible binding sites for lignin fragments and xylooligosaccharides that have not been previously reported. Investigations into the molecular determinants supporting the potential binding sites is being pursued.
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