Metabolic Regulation of a Bacterial Cell System with Emphasis on Escherichia coli Metabolism

It is quite important to understand the overall metabolic regulation mechanism of bacterial cells such as Escherichia coli from both science (such as biochemistry) and engineering (such as metabolic engineering) points of view. Here, an attempt was made to clarify the overall metabolic regulation mechanism by focusing on the roles of global regulators which detect the culture or growth condition and manipulate a set of metabolic pathways by modulating the related gene expressions. For this, it was considered how the cell responds to a variety of culture environments such as carbon (catabolite regulation), nitrogen, and phosphate limitations, as well as the effects of oxygen level, pH (acid shock), temperature (heat shock), and nutrient starvation.

Distinct Time-Resolved Roles for Two Catabolite-Sensing Pathways duringStreptococcus pyogenesInfection

ABSTRACTMany Gram-positive pathogens link the expression of virulence genes to the presence of carbon source substrates using overlapping pathways for global control of carbon catabolite regulation. However, how these pathways are integrated to control the behavior of the transcriptome in time- and compartment-specific patterns is typically not well understood. In the present study, global transcriptome profiling was used to determine the extent to which glucose alters gene expression inStreptococcus pyogenes(group A streptococcus) and the contributions of the CcpA and LacD.1 catabolite control pathways to the regulation of this responsein vitro. This analysis revealed that the expression of as many as 15% of the genes examined was regulated and that CcpA and LacD.1 together contribute to the regulation of 60% of this subset. However, numerous patterns were observed, including both CcpA- and LacD.1-specific and independent regulation, coregulation, and regulation of genes by these pathways independently of glucose. In addition, CcpA and LacD.1 had antagonistic effects on most coregulated genes. To resolve the roles of these regulators during infection, the expression of selected transcripts representative of different regulatory patterns was examined in a murine model of soft tissue infection. This revealed distinct patterns of misregulation with respect to time in CcpA−versus LacD.1−mutants. Taken together, these data support an important role for carbohydrate in the regulation of the transcriptome in tissue and suggest that the CcpA and LacD.1 pathways are organized to function at different times during the course of an infection.

Carbon Catabolite Repression of Type IV Pilus-Dependent Gliding Motility in the Anaerobic Pathogen Clostridium perfringens

ABSTRACT Clostridium perfringens is an anaerobic, gram-positive, spore-forming bacterium responsible for the production of severe histotoxic and gastrointestinal diseases in humans and animals. In silico analysis of the three available genome-sequenced C. perfringens strains (13, SM101, and ATCC13124) revealed that genes that encode flagellar proteins and genes involved in chemotaxis are absent. However, those strains exhibit type IV pilus (TFP)-dependent gliding motility. Since carbon catabolite regulation has been implicated in the control of different bacterial behaviors, we investigated the effects of glucose and other readily metabolized carbohydrates on C. perfringens gliding motility. Our results demonstrate that carbon catabolite regulation constitutes an important physiological regulatory mechanism that reduces the proficiencies of the gliding motilities of a large number of unrelated human- and animal-derived pathogenic C. perfringens strains. Glucose produces a strong dose-dependent inhibition of gliding development without affecting vegetative growth. Maximum gliding inhibition was observed at a glucose concentration (1%) previously reported to also inhibit other important behaviors in C. perfringens, such as spore development. The inhibition of gliding development in the presence of glucose was due, at least in part, to the repression of the genes pilT and pilD, whose products are essential for TFP-dependent gliding proficiency. The inhibitory effects of glucose on pilT and pilD expression were under the control of the key regulatory protein CcpA (catabolite control protein A). The deficiency in CcpA activity of a ccpA knockout C. perfringens mutant strain restored the expressions of pilT and pilD and gliding proficiency in the presence of 1% glucose. The carbon catabolite repression of the gliding motility of the ccpA mutant strain was restored after the introduction of a complementing plasmid harboring a wild-type copy of ccpA. These results point to a central role for CcpA in orchestrating the negative effect of carbon catabolite regulation on C. perfringens gliding motility. Furthermore, we discovered a novel positive role for CcpA in pilT and pilD expression and gliding proficiency in the absence of catabolite regulation. Carbon catabolite repression of gliding motility and the dual role of CcpA, either as repressor or as activator of gliding, are analyzed in the context of the different social behaviors and diseases produced by C. perfringens.