scholarly journals cAMP does not have an important role in carbon catabolite repression of the Escherichia coli lac operon

2009 ◽  
Vol 7 (3) ◽  
pp. 250-250 ◽  
Author(s):  
Atul Narang
Keyword(s):  
Escherichia Coli ◽  
Catabolite Repression ◽  
Carbon Catabolite Repression ◽  
Lac Operon

scholarly journals Effect of deregulation of repressor-specific carbon catabolite repression on carbon source consumption in Escherichia coli

2021 ◽  
Vol 64 (1) ◽  
Author(s):  
Hyeon Jeong Seong ◽  
Yu-Sin Jang
Keyword(s):  
Escherichia Coli ◽  
Carbon Source ◽  
Catabolite Repression ◽  
Sole Carbon Source ◽  
Carbon Catabolite Repression ◽  
Cell Factory ◽  
Essential Information ◽  
E Coli ◽  
Marine Biomass ◽  
Galactose Utilization

AbstractEscherichia coli has been used as a host to construct the cell factory for biobased production of chemicals from renewable feedstocks. Because galactose is found in marine biomass as a major component, the strategy for galactose utilization in E. coli has been gained more attention. Although galactose and glucose co-fermentation has been reported using the engineered E. coli strain, few reports have covered fermentation supplemented with galactose as a sole carbon source in the mutant lacking the repressor-specific carbon catabolite repression (CCR). Here, we report the effects of the deregulation of the repressor-specific CCR (galR− and galS−) in fermentation supplemented with galactose as a sole carbon source, using the engineered E. coli strains. In the fermentation using the galR− and galS− double mutant (GR2 strain), an increase of rates in sugar consumption and cell growth was observed compared to the parent strain. In the glucose fermentation, wild-type W3110 and its mutant GR2 and GR2PZ (galR−, galS−, pfkA−, and zwf−) consumed sugar at a higher rate than those values obtained from galactose fermentation. However, the GR2P strain (galR−, galS−, and pfkA−) showed no difference between fermentations using glucose and galactose as a sole carbon source. This study provides essential information for galactose fermentation using the CCR-deregulated E. coli strains.

Understanding carbon catabolite repression in Escherichia coli using quantitative models

2015 ◽  
Vol 23 (2) ◽  
pp. 99-109 ◽  
Author(s):  
A. Kremling ◽  
J. Geiselmann ◽  
D. Ropers ◽  
H. de Jong
Keyword(s):  
Escherichia Coli ◽  
Catabolite Repression ◽  
Carbon Catabolite Repression ◽  
Quantitative Models

scholarly journals Effect of point mutations in the lac promoter on transient and severe catabolite repression of the lac operon of Escherichia coli

1971 ◽  
Vol 123 (4) ◽  
pp. 579-584 ◽  
Author(s):  
M. D. Yudkin
Keyword(s):  
Escherichia Coli ◽  
Catabolite Repression ◽  
Point Mutations ◽  
Severe Form ◽  
Lac Operon ◽  
Wild Type ◽  
Diploid Strain ◽  
Transient Repression ◽  
Lac Promoter

1. Experiments were devised to show whether the point mutations L8 and L29 in the lac promoter alleviate transient repression. 2. Several recombinants were picked from matings between a single F−p+strain and Hfr strains carrying mutations L8 and L29. All of the 19 p−recombinants tested proved to suffer no transient repression, whereas all of the eight p+recombinants tested suffered prolonged transient repression. 3. A diploid strain was constructed in which more than 90% of the thiogalactoside transacetylase is synthesized from the episome with a wild-type lac promoter, whereas 100% of the β-galactosidase is synthesized from the chromosome with a promoter carrying mutation L8. In this diploid the synthesis of thiogalactoside transacetylase suffered transient repression but the synthesis of β-galactosidase did not. 4. Exactly similar results were obtained with a diploid strain in which the chromosomal promoter carried mutation L29. 5. The same diploid strains were used in experiments to show whether mutations L8 and L29 alleviate the severe catabolite repression caused by growth in glucose plus gluconate. In both strains glucose+gluconate repressed the synthesis of β-galactosidase much less than the synthesis of thiogalactoside transacetylase. 6. These and previously reported results can be explained by assuming (a) that both mutations L8 and L29 render the lac promoter partially, but not completely, insensitive to catabolite repression, and (b) that transient repression is an exceptionally severe form of catabolite repression.

scholarly journals Deconstructing glucose-mediated catabolite repression of the lac operon of Escherichia coli: I. Inducer exclusion, by itself, cannot account for the repression

2019 ◽  
Author(s):  
Ritesh K. Aggarwal ◽  
Atul Narang
Keyword(s):  
Escherichia Coli ◽  
Positive Feedback ◽  
Catabolite Repression ◽  
Feedback Loop ◽  
Lactose Permease ◽  
Lac Operon ◽  
Positive Feedback Loop ◽  
Inducer Exclusion ◽  
Transcriptional Inhibition

AbstractThe lac operon of Escherichia coli is repressed several 100-fold in the presence of glucose. This repression has been attributed to CRP-mediated transcriptional inhibition and EIIAGlc-mediated inducer exclusion. The growing evidence against the first mechanism has led to the postulate that the repression is driven by inducer exclusion. The literature shows that in fully induced cells, inducer exclusion reduces the permease activity only 2-fold. However, it is conceivable that inducer exclusion drastically reduces the permease activity in partially induced cells. We measured the decline of lactose permease activity due to inducer exclusion in partially induced cells, but found that the permease activity decreased no more than 6-fold. We show that the repression is small because these experiments are performed in the presence of chloramphenicol. Indeed, when glucose is added to a culture growing on glycerol and TMG, but no chloramphenicol, lac is repressed 900-fold. This repression is primarily due to reversal of the positive feedback loop, i.e., the decline of the intracellular TMG level leads to a lower permease level, which reduces the intracellular TMG level even further. The repression in the absence of chloramphenicol is therefore primarily due to positive feedback, which does not exist during measurements of inducer exclusion.

scholarly journals Regulation of Arabinose and Xylose Metabolism in Escherichia coli

2009 ◽  
Vol 76 (5) ◽  
pp. 1524-1532 ◽  
Author(s):  
Tasha A. Desai ◽  
Christopher V. Rao
Keyword(s):  
Gene Expression ◽  
Escherichia Coli ◽  
Catabolite Repression ◽  
Carbon Catabolite Repression ◽  
Plant Biomass ◽  
Xylose Metabolism ◽  
Sugar Utilization ◽  
E Coli ◽  
Metabolic Genes ◽  
Pentose Sugars

ABSTRACT Bacteria such as Escherichia coli will often consume one sugar at a time when fed multiple sugars, in a process known as carbon catabolite repression. The classic example involves glucose and lactose, where E. coli will first consume glucose, and only when it has consumed all of the glucose will it begin to consume lactose. In addition to that of lactose, glucose also represses the consumption of many other sugars, including arabinose and xylose. In this work, we characterized a second hierarchy in E. coli, that between arabinose and xylose. We show that, when grown in a mixture of the two pentoses, E. coli will consume arabinose before it consumes xylose. Consistent with a mechanism involving catabolite repression, the expression of the xylose metabolic genes is repressed in the presence of arabinose. We found that this repression is AraC dependent and involves a mechanism where arabinose-bound AraC binds to the xylose promoters and represses gene expression. Collectively, these results demonstrate that sugar utilization in E. coli involves multiple layers of regulation, where cells will consume first glucose, then arabinose, and finally xylose. These results may be pertinent in the metabolic engineering of E. coli strains capable of producing chemical and biofuels from mixtures of hexose and pentose sugars derived from plant biomass.

Sign in / Sign up

Export Citation Format

Share Document