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31.
Karl Rumbold Hugo JJ van Buijsen Karin M Overkamp Johan W van Groenestijn Peter J Punt J van der Mariët Werf 《Microbial cell factories》2009,8(1):1-11
Although many secondary metabolites with diverse biological activities have been isolated from myxobacteria, most strains
of these biotechnologically important gliding prokaryotes remain difficult to handle genetically. In this study we describe
the new fast growing myxobacterial thermophilic isolate GT-2 as a heterologous host for the expression of natural product
biosynthetic pathways isolated from other myxobacteria. According to the results of sequence analysis of the 16S rDNA, this
moderately thermophilic isolate is closely related to Corallococcus macrosporus and was therefore named C. macrosporus GT-2. Fast growth of moderately thermophilic strains results in shorter fermentation and generation times, aspects which are of
significant interest for molecular biological work as well as production of secondary metabolites. Development of a genetic
manipulation system allowed the introduction of the complete myxochromide biosynthetic gene cluster, located on a transposable
fragment, into the chromosome of GT-2. Genetic engineering of the biosynthetic gene cluster by promoter exchange leads to
much higher production of myxochromides in the heterologous host C. macrosporus GT-2 in comparison to the original producer Stigmatella aurantiaca and to the previously described heterologous host Pseudomonas putida (600 mg/L versus 8 mg/L and 40 mg/L, respectively). 相似文献
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33.
Horton AC Mahadevan NR Ruvinsky I Gibson-Brown JJ 《Journal of experimental zoology. Part B. Molecular and developmental evolution》2003,299(1):41-53
The widely accepted notion that two whole-genome duplications occurred during early vertebrate evolution (the 2R hypothesis) stems from the fact that vertebrates often possess several genes corresponding to a single invertebrate homolog. However the number of genes predicted by the Human Genome Project is less than twice as many as in the Drosophila melanogaster or Caenorhabditis elegans genomes. This ratio could be explained by two rounds of genome duplication followed by extensive gene loss, by a single genome duplication, by sequential local duplications, or by a combination of any of the above. The traditional method used to distinguish between these possibilities is to reconstruct the phylogenetic relationships of vertebrate genes to their invertebrate orthologs; ratios of invertebrate-to-vertebrate counterparts are then used to infer the number of gene duplication events. The lancelet, amphioxus, is the closest living invertebrate relative of the vertebrates, and unlike protostomes such as flies or nematodes, is therefore the most appropriate outgroup for understanding the genomic composition of the last common ancestor of all vertebrates. We analyzed the relationships of all available amphioxus genes to their vertebrate homologs. In most cases, one to three vertebrate genes are orthologous to each amphioxus gene (median number=2). Clearly this result, and those of previous studies using this approach, cannot distinguish between alternative scenarios of chordate genome expansion. We conclude that phylogenetic analyses alone will never be sufficient to determine whether genome duplication(s) occurred during early chordate evolution, and argue that a "phylogenomic" approach, which compares paralogous clusters of linked genes from complete amphioxus and human genome sequences, will be required if the pattern and process of early chordate genome evolution is ever to be reconstructed. 相似文献
34.
Molecular evolution of rodent insulins 总被引:1,自引:0,他引:1
Several trees of amino acid sequences of rodent insulins were derived with
the maximum-parsimony procedure. Possible orthologous and paralogous
relationships were investigated. Except for a recent gene duplication in
the ancestor of rat and mouse, there are no strong arguments for other
paralogous relationships. Therefore, a tree in agreement with other
biological data is the most reasonable one. According to this tree, the
capacity to form zinc-binding hexamers was lost once in the ancestor of the
hystricomorph rodents, followed by moderately increased evolutionary rates
in the lineages to African porcupine and chinchilla but highly increased
rates in at least three independent lines to other taxa of this suborder:
guinea pig, cuis, and Octodontoidea (coypu and casiragua).
相似文献
35.
Previously, treatment of Tamm-Horsfall glycoprotein (THp) from different
donors with endo-beta-galactosidase has been shown to liberate a tetra- and
a Sd(a)-active pentasaccharide, concluding the presence of N-linked
carbohydrate chains containing additional N - acetyllactosamine units.
These type of oligosaccharides were not found in a detailed structure
elucidation of the carbohydrate moiety of THp of one male donor, suggesting
a donor-specific feature for these type of structures. Therefore, THp was
isolated from four healthy male donors and each subjected to
endo-beta-galactosidase treatment in order to release these tetra- and
Sd(a)-active pentasaccharide. Differences were observed in the total amount
of released tetra- and Sda-active pentasaccharide of the used donors (42,
470, 478, 718 microg/100 mg THp), indicating that the presence of repeating
N-acetyllactosamine units incorporated into the N-glycan moiety of THp is
donor specific. Furthermore, a higher expression of the Sd(a) determinant
on antennae which display N-acetyllactosamine elongation was observed,
suggesting a better accessibility for the
beta-N-acetylgalactosaminyltransferase. In order to characterize the
N-glycans containing repeating N- acetyllactosamine units, carbohydrate
chains were enzymatically released from THp and isolated. The
tetraantennary fraction, which accounts for more than 33% of the total
carbohydrate moiety of THp, was used to isolate oligosaccharides containing
additional N - acetyllactosamine units. Five N-linked tetraantennary
oligosaccharides containing a repeating N-acetyllactosamine unit were
identified, varying from structures bearing four Sd(a) determinants to
structures containing no Sd(a) determinant (see below). One compound was
used in order to specify the branch location of the additional N-
acetyllactosamine unit, and it appeared that only the Gal-6' and Gal-8'
residues were occupied by a repeating N -acetyllactosamine unit.
相似文献
36.
37.
Ecology and management of mahogany (Swietenia macrophylla King) in the Chimanes Forest, Bed, Bolivia
R.E. GULLISON S.N. PANFIL JJ. STROUSE S.P. HUBBELL 《Botanical journal of the Linnean Society. Linnean Society of London》1996,122(1):9-34
Mahogany ( Swietenia macrophylla King) regenerates in areas of erosion on high terraces and in forest killed by flooding and deposition of alluvial sediments in the Chimanes Forest, Bolivia. These hydrological disturbances are patchy, and only one of five stands of mahogany that we inventoried was regenerating. Mahogany survives these disturbances significantly better than the common tree species. The long time between disturbances appears to favour late maturation. Mahogany trees allocate little photosynthates to reproduction until they are very large emergents, at least 80 cm in diameter. The episodic nature of the regeneration sites means that mahogany stands are composed of one or a few cohorts, which are vulnerable to overharvesting, particularly with the current use of a minimum cutting diameter to regulate harvest. The delayed onset of fecundity means that the small trees that escape harvest are not very fecund, resulting in minimal seed input to logged forest. Only 7–9% of the gaps created by logging contain natural regeneration after 20 + yr. A successful management plan for mahogany would entail a monocyclic harvest, with a rotation age of 100 + years, the estimated time that it takes for trees to achieve commercial size in natural forest. Since the number of seed trees that will be left is small, they should be concentrated in sites that are likely to be conducive to natural regeneration, such as near rivers and flood damaged forest. Seed production will be maximized for a given basal area (opportunity cost to loggers) if trees c. 110 cm dbh are selected as seed trees. The mahogany stocks in the Chimanes Forest are nearly exhausted, but the findings of this study could be used to help rebuild the mahogany populations, or to design management plans for the commercial species that have similar ecologies to mahogany. 相似文献
38.
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40.
Annette AM Gerritsen Rob JPM Scholten Willem JJ Assendelft Herman Kuiper Henrica CW de Vet Lex M Bouter 《BMC neurology》2001,1(1):8-7