Isolation and structure elucidation of a novel griseorhodin.
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Three antibiotics possessing cytotoxic properties were isolated from a strain of Streptomyces griseus (FCRC-57). One was found to be identical with griseorhodin A. A second, FCRC-57-U, was found to be identical to griseorhodin C. FCRC-57-G is a new antibiotic structurally related to griseorhodins A and C, and is active against KB cells in vitro. The structure of this new antibiotic was determined using mass spectrometry, proton and carbon nuclear magnetic resonance spectroscopy and synthesis. (+info)
Feigrisolides A, B, C and D, new lactones with antibacterial activities from Streptomyces griseus.
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Four new lactone compounds, named feigrisolides A to D (1 to 4), have been isolated from Streptomyces griseus. The chemical structures were determined by detail analysis of their spectroscopic data and chemical transformations. Structurally, the feigrisolides A (1) and B (2) are hepta-lactones, feigrisolide C (3) and D (4) are 16-membered macrodiolides. Biological studies showed that feigrisolide B (2) exhibited strong antibacterial, as well as medium cyctotoxic, and antiviral activities. Feigrisolides A (1), C (3) and D (4) are medium inhibitors of 3alpha-hydroxysteroid-dehydrogenase (3alpha-HSD) inhibiting activity. (+info)
Isolation of mutants deregulated in phosphate control of candicidin biosynthesis.
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Mutants have been isolated in which phosphate does not inhibit the biosynthesis of candicidin. At high phosphate concentrations, candicidin production by phosphate-deregulated mutants is still inhibited, but to a lesser extent than in the wild type. Some of these mutants are higher candicidin producers than the wild type, not only in phosphate-supplemented medium but also in non-supplemented production medium. The high candicidin production by these mutants is due to (1) a high specific rate of candicidin biosynthesis and (2) an extended production phase. None of the phosphate-deregulated mutants in which uptake of [32P]phosphate was measured was a phosphate-permeability mutant. (+info)
Kinetics of methyl t-butyl ether cometabolism at low concentrations by pure cultures of butane-degrading bacteria.
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Butane-oxidizing Arthrobacter (ATCC 27778) bacteria were shown to degrade low concentrations of methyl t-butyl ether (MTBE; range, 100 to 800 microg/liter) with an apparent half-saturation concentration (K(s)) of 2.14 mg/liter and a maximum substrate utilization rate (k(c)) of 0.43 mg/mg of total suspended solids per day. Arthrobacter bacteria demonstrated MTBE degradation activity when grown on butane but not when grown on glucose, butanol, or tryptose phosphate broth. The presence of butane, tert-butyl alcohol, or acetylene had a negative impact on the MTBE degradation rate. Neither Methylosinus trichosporium OB3b nor Streptomyces griseus was able to cometabolize MTBE. (+info)
Identification and characterization of a developmentally regulated protein, EshA, required for sporogenic hyphal branches in Streptomyces griseus.
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To identify sporulation-specific proteins that might serve as targets of developmental regulatory factors in Streptomyces, we examined total proteins of Streptomyces griseus by two-dimensional gel electrophoresis. Among five proteins that were present at high levels during sporulation but absent from vegetative cells, two of the proteins, P3 and P4, were absent from developmental mutants that undergo aberrant morphogenesis. The deduced amino acid sequence of the gene that encodes P3 (EshA) showed extensive similarity to proteins from mycobacteria and a cyanobacterium, Synechococcus, that are abundant during nutritional stress but whose functions are unknown. Uniquely among these proteins, EshA contains a cyclic nucleotide-binding domain, suggesting that the activity of EshA may be modulated by a cyclic nucleotide. The eshA gene was strongly expressed from a single transcription start site only during sporulation, and accumulation of the eshA transcript depended on a developmental gene, bldA. During submerged sporulation, a null mutant strain that produced no EshA could not extend sporogenic hyphae from new branch points but instead accelerated septation and spore maturation at the preexisting vegetative filaments. These results indicated that EshA is required for the growth of sporogenic hyphae and localization of septation and spore maturation but not for spore viability. (+info)
Substrate analysis and molecular cloning of the extracellular alkaline phosphatase of Streptomyces griseus.
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Streptomyces species secrete large amounts of alkaline phosphatase (AP) enzymes that have not been characterized so far. An AP has been purified to homogeneity from cultures of Streptomyces griseus IMRU 3570. The enzyme has a monomer size of 62 kDa and is processed in the culture to a 33 kDa protein as shown by immunoblotting. The enzyme was purified by ammonium sulfate precipitation, CM-Sephadex cationic exchange, chromatofocusing and HPLC Sphaerogel 3000SW filtration. The pure enzyme uses a variety of organic phosphorylated compounds as substrates. The N-terminal end of the mature protein was found to be RLREDPFTLGVASGDPHP. The gene phoA has been cloned using as probe an oligomer based on the N-terminal sequence of the S. griseus AP. phoA encodes a protein of 62678 Da with low homology to the AP of Escherichia coli. The phoA gene was found to be homologous to three alkaline-phosphatase-encoding genes previously identified in the Streptomyces coelicolor genome. On the basis of the optimal pH, substrate specificity and differences in amino acid sequence of motifs defining the active centre of APs, the S. griseus AP uses a wide range of organic phosphate substrates and is different from the phosphatases of Gram-negative bacteria. (+info)
Differential regulation of ftsZ transcription during septation of Streptomyces griseus.
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Streptomyces has been known to form two types of septa. The data in this research demonstrated that Streptomyces griseus forms another type of septum near the base of sporogenic hyphae (basal septum). To understand the regulation of the septation machinery in S. griseus, we investigated the expression of the ftsZ gene. S1 nuclease protection assays revealed that four ftsZ transcripts were differentially expressed during morphological differentiation. The vegetative transcript (emanating from P(veg)) is present at a moderate level during vegetative growth, but is switched off within the first 2 h of sporulation. Two sporulation-specific transcripts predominantly accumulated, and the levels increased by approximately fivefold together shortly before sporulation septa begin to form. Consistently, the sporulation-specific transcripts were expressed much earlier and more abundantly in a group of nonsporulating mutants that form their sporulation septa prematurely. Promoter-probe studies with two different reporter systems confirmed the activities of the putative promoters identified from the 5' end point of the transcripts. The levels and expression timing of promoter activities were consistent with the results of nuclease protection assays. The aseptate phenotype of the P(spo) mutant indicated that the increased transcription from P(spo) is required for sporulation septation, but not for vegetative or basal septum formation. (+info)
Properties and substrate specificity of RppA, a chalcone synthase-related polyketide synthase in Streptomyces griseus.
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RppA, a chalcone synthase-related polyketide synthase (type III polyketide synthase) in the bacterium Streptomyces griseus, catalyzes the formation of 1,3,6,8-tetrahydroxynaphthalene (THN) from five molecules of malonyl-CoA. The K(m) value for malonyl-CoA and the k(cat) value for THN synthesis were determined to be 0.93 +/- 0.1 microm and 0.77 +/- 0.04 min(-1), respectively. RppA accepted aliphatic acyl-CoAs with the carbon lengths from C(4) to C(8) as starter substrates and catalyzed sequential condensation of malonyl-CoA to yield alpha-pyrones and phloroglucinols. In addition, RppA yielded a hexaketide, 4-hydroxy-6-(2',4',6'-trioxotridecyl)-2-pyrone, from octanoyl-CoA and five molecules of malonyl-CoA, suggesting that the size of the active site cavity of RppA is larger than any other chalcone synthase-related enzymes found so far in plants and bacteria. RppA was also found to synthesize a C-methylated pyrone, 3,6-dimethyl-4-hydroxy-2-pyrone, by using acetoacetyl-CoA as the starter and methylmalonyl-CoA as an extender. Thus, the broad substrate specificity of RppA yields a wide variety of products. (+info)