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BMC Microbiol ; 7: 53, 2007 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-17559662

RESUMO

BACKGROUND: Glucose is the preferred carbon and energy source for Escherichia coli. A complex regulatory network coordinates gene expression, transport and enzyme activities in response to the presence of this sugar. To determine the extent of the cellular response to glucose, we applied an approach combining global transcriptome and regulatory network analyses. RESULTS: Transcriptome data from isogenic wild type and crp- strains grown in Luria-Bertani medium (LB) or LB + 4 g/L glucose (LB+G) were analyzed to identify differentially transcribed genes. We detected 180 and 200 genes displaying increased and reduced relative transcript levels in the presence of glucose, respectively. The observed expression pattern in LB was consistent with a gluconeogenic metabolic state including active transport and interconversion of small molecules and macromolecules, induction of protease-encoding genes and a partial heat shock response. In LB+G, catabolic repression was detected for transport and metabolic interconversion activities. We also detected an increased capacity for de novo synthesis of nucleotides, amino acids and proteins. Cluster analysis of a subset of genes revealed that CRP mediates catabolite repression for most of the genes displaying reduced transcript levels in LB+G, whereas Fis participates in the upregulation of genes under this condition. An analysis of the regulatory network, in terms of topological functional units, revealed 8 interconnected modules which again exposed the importance of Fis and CRP as directly responsible for the coordinated response of the cell. This effect was also seen with other not extensively connected transcription factors such as FruR and PdhR, which showed a consistent response considering media composition. CONCLUSION: This work allowed the identification of eight interconnected regulatory network modules that includes CRP, Fis and other transcriptional factors that respond directly or indirectly to the presence of glucose. In most cases, each of these modules includes genes encoding physiologically related functions, thus indicating a connection between regulatory network topology and related cellular functions involved in nutrient sensing and metabolism.


Assuntos
Escherichia coli/metabolismo , Regulação Bacteriana da Expressão Gênica/fisiologia , Redes Reguladoras de Genes , Glucose/metabolismo , Análise por Conglomerados , Meios de Cultura/química , Proteína Receptora de AMP Cíclico/genética , Proteína Receptora de AMP Cíclico/fisiologia , Escherichia coli/genética , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/fisiologia , Fator Proteico para Inversão de Estimulação/fisiologia , Deleção de Genes , Perfilação da Expressão Gênica , Regulação Bacteriana da Expressão Gênica/genética , Redes e Vias Metabólicas/genética , Análise de Sequência com Séries de Oligonucleotídeos , RNA Bacteriano/biossíntese , RNA Bacteriano/genética , RNA Mensageiro/biossíntese , RNA Mensageiro/genética , Regulon , Fatores de Transcrição/genética , Fatores de Transcrição/fisiologia
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