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  • 1
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Spo0A is a phosphorylation-activated transcription factor of Bacillus subtilis. It is a member of the response regulator super-family of bacterial signal transduction proteins and controls many of the changes in gene expression that occur during the transition into stationary phase and during the initiation of speculation. To identify the domains of Spo0A most critical for determining its structural and functional features, presumptive homologues of the spo0A gene were characterized in a collection of eight Bacillus species and six Clostridium species representing phylogenetically diverse members of these genera. An alignment of the partial or complete DNA sequences of these homologues revealed three regions of especially high conservation in the effector domain. We speculate that the most highly conserved of these corresponds to the recognition helix of a putative helix-turn-helix motif, and, therefore, represents the actual DNA-contacting surface of the protein. In the case of homologues identified in Bacillus anthracis and Clostridium acetobutylicum and retrieved by polymerase chain reaction amplification, we confirmed by gene-disruption analysis that the homologue actually is required for initiation of sporulation. Apparent homologues of the B. subtilis spolVB gene were also discovered immediately upstream from the spo0A homologues in all Bacillus and Clostridium species examined. The discovery of homologues of B. subtilis sporulation genes in these diverse species implies that the gene products required for specifying pathways of sporulation-specific gene activation and for determining key morphogenetic changes may be highly conserved and suggests that an approach similar to that undertaken here might be used as a general strategy to retrieve and compare their gene sequences. Exhaustive efforts to detect a spo0A-like gene in non-endospore formers, including close relatives of Bacillus such as Listeria and Staphylococcus, were uniformly unsuccessful, suggesting that regulation of gene activity during the transition into stationary phase mediated by Spo0A-like proteins may be exclusive to the endospore-forming bacteria.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Mutants of Streptomyces coelicolor blocked at the earliest visible stage of morphological differentiation are called bld mutants. These mutants fail to form aerial hyphae on rich medium and most are defective in antibiotic production. One striking feature of these mutants is that, with the exception of bldB, their morphological defect is carbon-source dependent. In our investigation of catabolite control in Streptomyces, we identified mutants that were resistant to glucose repression and were also bld. The existence of these new bld mutants led us to examine the catabolite control phenotype of the previously described bld mutants which were not known to contain defects in carbon regulation. We report here that all of the characterized bld mutants of S.coelicolor are defective in the regulation of galP1, and that at least one of the bld mutants, bldB, is globally deregulated for carbon utilization. Complementation of the morphological defect of bldA and bldB mutants with a cloned copy of the wild-type bld gene simultaneously restored normal regulation of galP1, indicating that both aspects of the mutant phenotype are caused by the same lesion. We suggest a new interpretation for the role of the bld genes in development in Streptomyces. We suggest that the primary defect in bld mutants is in the regulation of carbon utilization, not specifically in the activation of genes whose products regulate the development pathway as previously suggested. We speculate that the inability of bld mutants to initiate morphogenesis is a secondary consequence of their inability to sense and/or signal starvation.
    Type of Medium: Electronic Resource
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