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  • Blackwell Science Ltd  (3)
  • Blackwell Scientific Publications  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Unusual regulatory mechanism for a Streptomyces multidrug resistance gene, ptr, involving three homologous protein-binding sites overlapping the promoter region (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Scientific Publications
    Molecular microbiology 17 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A promoter controlling expression of the pristinamycin multidrug resistance gene (ptr), originally isolated from Streptomyces pristinaespiralis, is inducible by many toxic compounds in various Streptomyces species. Studies of ptr promoter control were carried out in the heterologous host, Streptomyces lividans. In S. lividans, a regulatory protein or a protein complex (Pip), identified by its ability to bind to the ptr promoter in gel-retardation experiments, was induced by pristinamycin I (PI). In situ copper-phenanthroline foot-printing analysis identified three (A, B, and C) similar Pip-binding sites having the sequence GTACA(C/G)CGTA(C/T). These sites overlapped with functionally important regions of the promoter: the ‘A’ site overlapped with the −35 hexamer, ‘B’ overlapped with the −10 hexamer and ‘C’ was located between the transcription start site and the Shine—Dalgarno sequence. A GT—AG dinucleotide mutation was introduced at positions 8–9 of the consensus sequence to generate seven variant promoters: three mutated in one of the three sites, three mutated in two sites, and one mutated in all three sites. Whereas these promoters had reduced antibiotic (PI)-induced activity, their levels of expression in the absence of PI was higher. This suggested an unusual regulatory mechanism in which Pip could act either as an activator or repressor. Gel shift experiments revealed Pip or its homologues in many other Streptomyces species, suggesting that it is widely employed in the regulation of antibiotic resistance genes and perhaps secondary metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_17061109.x
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  • 2
    Electronic Resource
    Electronic Resource
    Specialized osmotic stress response systems involve multiple SigB-like sigma factors in Streptomyces coelicolor (2003)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 47 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Whereas in Bacillus subtilis, a general stress response stimulon under the control of a single sigma factor (SigB) is induced by different physiological and environmental stresses (heat, salt or ethanol shock), in Streptomyces coelicolor, these environmental stresses induce independent sets of proteins, and its genome encodes nine SigB paralogues. To investigate possible functions of multiple sigB-like genes in S. coelicolor, Pctc, a promoter routinely used to assay SigB activity in vivo, was analysed as a heterologous reporter. The fact that Pctc was activated by osmotic shock, but not by heat or ethanol, confirmed that stress response system(s) could operate independently in S. coelicolor. Pctc was also induced transiently during growth of liquid cultures, presumably by nutritional signals. We purified an RNA polymerase holoenzyme from crude extracts that catalysed specific transcription of Pctc in vitro. Its sigma subunit was identified as a product of the sigH gene, which is co-transcribed downstream of a putative antisigma factor gene (prsH). Although the sigH function was not needed for normal colony morphology, prsH was conditionally required for both aerial hyphae formation and regulation of antibiotic biosynthesis. Levels of two different sigH-encoded proteins were growth phase dependent but not significantly changed by osmotic stress, implying the important roles of post-translational regulatory elements such as PrsH. In addition, synthesis of three other SigH-like proteins was induced by osmotic stress, but not by ethanol or heat. Two of them were genetically assigned to sigH homologous loci sigI and sigJ and shown to be independently regulated. This family of SigH-like proteins displayed different osmotic response kinetics. Thus, in contrast to many other bacteria, S. coelicolor uses an osmotic sensory system that can co-ordinate the activity of multiple paralogues to control the relative activity of promoters within the same stress stimulon. Such specialized stress response systems may reflect adaptive functions needed for colonial differentiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03302.x
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  • 3
    Electronic Resource
    Electronic Resource
    Proteomic studies of diauxic lag in the differentiating prokaryote Streptomyces coelicolor reveal a regulatory network of stress-induced proteins and central metabolic enzymes (2003)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 48 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Bacteria typically undergo intermittent periods of starvation and adaptation, emulated as diauxic growth in the laboratory. In association with growth arrest elicited by metabolic stress, the differentiating eubacterium Streptomyces coelicolor not only adapts its primary metabolism, but can also activate developmental programmes leading to morphogenesis and antibiotic biosynthesis. Here, we report combined proteomic and metabolomic data of S. coelicolor used to analyse global changes in gene expression during diauxic growth in a defined liquid medium. Cultures initially grew on glutamate, providing the nitrogen source and feeding carbon (as 2-oxoglutarate) into the TCA cycle, followed by a diauxic delay allowing reorientation of metabolism and a second round of growth supported by NH4+, formed during prediauxic phase, and maltose, a glycolytic substrate. Cultures finally entered stationary phase as a result of nitrogen starvation. These four physiological states had previously been defined statistically by their distinct patterns of protein synthesis and heat shock responses. Together, these data demonstrated that the rates of synthesis of heat shock proteins are determined not only by temperature increase but also by the patterns and rates of metabolic flux in certain pathways. Synthesis profiles for metabolic- and stress-induced proteins can now be interpreted by the identification of 204 spots (SWICZ database presented at ). Cluster analysis showed that the activity of central metabolic enzymes involved in glycolysis, the TCA cycle, starvation or proteolysis each displayed identifiable patterns of synthesis that logically underlie the metabolic state of the culture. Diauxic lag was accompanied by a structured regulatory programme involving the sequential activation of heat-, salt-, cold- and bacteriostatic antibiotic (pristinamycin I, PI)-induced stimulons. Although stress stimulons presumably provide protection during environmental- or starvation-induced stress, their identities did not reveal any coherent adaptive or developmental functions. These studies revealed interactive regulation of metabolic and stress response systems including some proteins known to support developmental programmes in S. coelicolor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03529.x
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  • 4
    Electronic Resource
    Electronic Resource
    A central regulator of morphological differentiation in the multicellular bacterium Streptomyces coelicolor (2002)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 46 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In the multicellular bacterium Streptomyces coelicolor, functions of developmental (bald) genes are required for the biosynthesis of SapB, a hydrophobic peptidic morphogen that facilitates aerial hyphae formation. Here, we show that aerial hyphal growth and SapB biosynthesis could be activated independently from the normal developmental cascade by providing unprogrammed expression of functionally interactive genes within the ram cluster. ramC, ramS and ramR were essential for normal growth of aerial hyphae, and ramR, a response regulator gene, was a key activator of development. The ramR gene restored growth of aerial hyphae and SapB formation in all bald strains tested (albeit only weakly in the bldC mutant), many of which are characterized by physiological defects. Disruption of the ramR gene abolished SapB biosynthesis and severely delayed growth of aerial hyphae. Transcription of ramR was developmentally controlled, and RamR function in vivo depended on its putative phosphorylation site (D53). We identified and mapped RamR targets immediately upstream of the region encoding ramC and ramS, a putative operon. Overexpression of ramR in the wild-type strain increased SapB levels and caused a distinctive wrinkled surface topology. Based on these results, we propose that phenotypes of bald mutations reflect an early stage in the Streptomyces developmental programme similar to the spo0 mutations in the unicellular bacterium Bacillus subtilis, and that RamR has analogies to Spo0A, the Bacillus response regulator that integrates physiological signals before triggering endospore formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.03255.x
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