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1.
Margareta Veligaj Mirjana Filipovi Jasenka Pigac Daslav Hranueli 《Applied microbiology》1981,41(4):986-991
The infection of Streptomyces rimosus by the virulent actinophage RP1 was partially characterized. RP1 infection of the host cells results in a dramatic decrease in viable cell count, followed by reduced antibiotic production. Phage-resistant mutants were isolated after mutagenic treatment and RP1 selective pressure. Characterization of the isolated mutants has revealed that RP1 infection had no influence on their growth and antibiotic production. However, multiplication of the phage particles in the lawns of resistant mutants was detected. Since these strains differ from the wild type in RP1 relative efficiency of plating, plaque morphology, and the time necessary for plaque appearance, they are considered to be semiresistant mutants. The propagation of RP1 on semiresistant strains is characterized by lower adsorption of phage particles and longer latent and rise periods. As a consequence, the multiplication of the phage is slower than that of their host, which consequently reduces the ratio of phage to its host, thus diluting out the phage. 相似文献
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Starcevic A Diminic J Zucko J Elbekali M Schlosser T Lisfi M Vukelic A Long PF Hranueli D Cullum J 《Journal of industrial microbiology & biotechnology》2011,38(9):1295-1304
An in silico model for homoeologous recombination between gene clusters encoding modular polyketide synthases (PKS) or non-ribosomal
peptide synthetases (NRPS) was developed. This model was used to analyze recombination between 12 PKS clusters from Streptomyces species and related genera to predict if new clusters might give rise to new products. In many cases, there were only a limited
number of recombination sites (about 13 per cluster pair), suggesting that recombination may pose constraints on the evolution
of PKS clusters. Most recombination events occurred between pairs of ketosynthase (KS) domains, allowing the biosynthetic
outcome of the recombinant modules to be predicted. About 30% of recombinants were predicted to produce polyketides. Four
NRPS clusters from Streptomyces strains were also used for in silico recombination. They yielded a comparable number of recombinants to PKS clusters, but
the adenylation (A) domains contained the largest proportion of recombination events; this might be a mechanism for producing
new substrate specificities. The extreme G + C-content, the presence of linear chromosomes and plasmids, as well as the lack
of a mutSL-mismatch repair system should favor production of recombinants in Streptomyces species. 相似文献
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Hrvoje Petkovi John Cullum Daslav Hranueli Iain S. Hunter Nataa Peri-Concha Jasenka Pigac Arinthip Thamchaipenet Duica Vujaklija Paul F. Long 《Microbiological reviews》2006,70(3):704-728
From a genetic standpoint, Streptomyces rimosus is arguably the best-characterized industrial streptomycete as the producer of oxytetracycline and other tetracycline antibiotics. Although resistance to these antibiotics has reduced their clinical use in recent years, tetracyclines have an increasing role in the treatment of emerging infections and noninfective diseases. Procedures for in vivo and in vitro genetic manipulations in S. rimosus have been developed since the 1950s and applied to study the genetic instability of S. rimosus strains and for the molecular cloning and characterization of genes involved in oxytetracycline biosynthesis. Recent advances in the methodology of genome sequencing bring the realistic prospect of obtaining the genome sequence of S. rimosus in the near term. 相似文献
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Background
The success of tropical reef-building corals depends on the metabolic co-operation between the animal host and the photosynthetic performance of endosymbiotic algae residing within its cells. To examine the molecular response of the coral Acropora microphthalma to high levels of solar irradiance, a cDNA library was constructed by PCR-based suppression subtractive hybridisation (PCR-SSH) from mRNA obtained by transplantation of a colony from a depth of 12.7 m to near-surface solar irradiance, during which the coral became noticeably paler from loss of endosymbionts in sun-exposed tissues.Methodology/Principal Findings
A novel approach to sequence annotation of the cDNA library gave genetic evidence for a hypothetical biosynthetic pathway branching from the shikimic acid pathway that leads to the formation of 4-deoxygadusol. This metabolite is a potent antioxidant and expected precursor of the UV-protective mycosporine-like amino acids (MAAs), which serve as sunscreens in coral phototrophic symbiosis. Empirical PCR based evidence further upholds the contention that the biosynthesis of these MAA sunscreens is a ‘shared metabolic adaptation’ between the symbiotic partners. Additionally, gene expression induced by enhanced solar irradiance reveals a cellular mechanism of light-induced coral bleaching that invokes a Ca2+-binding synaptotagmin-like regulator of SNARE protein assembly of phagosomal exocytosis, whereby algal partners are lost from the symbiosis.Conclusions/Significance
Bioinformatics analyses of DNA sequences obtained by differential gene expression of a coral exposed to high solar irradiance has revealed the identification of putative genes encoding key steps of the MAA biosynthetic pathway. Revealed also by this treatment are genes that implicate exocytosis as a cellular process contributing to a breakdown in the metabolically essential partnership between the coral host and endosymbiotic algae, which manifests as coral bleaching. 相似文献7.
Recombination between the linear plasmid pPZG101 and the linear chromosome of Streptomyces rimosus can lead to exchange of ends 总被引:5,自引:4,他引:1
Suada Pandza Goran Biukovi rea Paravi Ali Dadbin John Cullum & Daslav Hranueli 《Molecular microbiology》1998,28(6):1165-1176
The 387 kb linear plasmid pPZG101 of Streptomyces rimosus R6 can integrate into the chromosome or form a prime plasmid carrying the oxytetracycline biosynthesis cluster. The integration of plasmid pPZG101 into the linear chromosome of S. rimosus R6-501 in mutant MV25 was shown to be due to a single cross-over at a 4 bp common sequence. pPZG101 had integrated into a 250 kb DNA sequence that was reiterated at a low level. This sequence includes the oxytetracycline biosynthesis cluster, so that homologous recombination generated a mixed population carrying different copy numbers of the region. The 1 Mb linear plasmid pPZG103 in mutant MV17 had also arisen from a cross-over between pPZG101 and the chromosome, so that one end of pPZG103 consists of c . 850 kb of chromosomal sequence including the oxytetracycline biosynthesis cluster. The plasmid pPZG101 was shown to consist of a unique central region of about 30 kb flanked by terminal inverted repeats of about 180 kb. Analysis of a presumed ancestor plasmid pPZG102 suggested that the long terminal repeats had arisen by a recombination event during the strain development programme. 相似文献
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Pavle Goldstein Jurica Zucko Du?ica Vujaklija Anita Kri?ko Daslav Hranueli Paul F Long Catherine Etchebest Bojan Basrak John Cullum 《BMC bioinformatics》2009,10(1):335
Background
The number of protein family members defined by DNA sequencing is usually much larger than those characterised experimentally. This paper describes a method to divide protein families into subtypes purely on sequence criteria. Comparison with experimental data allows an independent test of the quality of the clustering. 相似文献9.
The development of a protoplast fusion technique for oxytetracycline-producing Streptomyces rimosus strains, and its evaluation for the application for a breeding programme, has been described. Treatment of S. rimosus protoplasts with 40% (w/v) PEG 1550 for 30 min gave optimal numbers of recombinants ranging from 1 to 10% of the total progeny. Therefore, by comparison with conjugation, protoplast fusion increased the frequency of recombination by two to three orders of magnitude. The proportion of multiple crossover classes amongst recombinants was higher, by a factor of ten, after protoplast fusion (13.3%) than after conjugation (1.5%). Participation of less frequent complementary genotype doubled from 9.0% in conjugation to 17.9% in protoplast fusion. Overall, this suggested that the opportunities for crossing over in a fusion of S. rimosus protoplasts were spatially and/or temporally extended leading to a loosening of linkage with a near-random assortment of genotypes in a cross. However, by minimizing the multiple crossover classes and calculating allele frequency gradients, it was shown that the protoplast fusion technique allows arrangement of genetic markers on the S. rimosus chromosome. These are ideal characteristics for the recombination of divergent lines in a strain improvement programme. 相似文献
10.
Recombinatorial biosynthesis of polyketides 总被引:1,自引:0,他引:1
Starcevic A Wolf K Diminic J Zucko J Ruzic IT Long PF Hranueli D Cullum J 《Journal of industrial microbiology & biotechnology》2012,39(3):503-511
Modular polyketide synthases (PKSs) from Streptomyces and related genera of bacteria produce many important pharmaceuticals. A program called CompGen was developed to carry out in silico homologous recombination between gene clusters encoding PKSs and determine whether recombinants
have cluster architectures compatible with the production of polyketides. The chemical structure of recombinant polyketides
was also predicted. In silico recombination was carried out for 47 well-characterised clusters. The predicted recombinants
would produce 11,796 different polyketide structures. The molecular weights and average degree of reduction of the chemical
structures are dispersed around the parental structures indicating that they are likely to include pharmaceutically interesting
compounds. The details of the recombinants and the chemical structures were entered in a database called r-CSDB. The virtual compound library is a useful resource for computer-aided drug design and chemoinformatics strategies for finding
pharmaceutically relevant chemical entities. A strategy to construct recombinant Streptomyces strains to produce these polyketides is described and the critical steps of mobilizing large biosynthetic clusters and producing
new linear cloning vectors are illustrated by experimental data. 相似文献