Characterization of a β-Glucoside Operon (<i>bgc</i>) Prevalent in Septicemic and Uropathogenic<i>Escherichia coli</i>Strains

Neelakanta, Girish; Sankar, T. Sabari; Schnetz, Karin

doi:10.1128/aem.02621-08

Cited by 9 publications

(11 citation statements)

References 39 publications

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“…Blast searches with BguR revealed high similarity of this protein with the previously characterized GntR-type transcriptional regulator GmuR in Bacillus subtilis [41], BgcR in Escherichia coli [42] and DasR in Streptomyces coelicolor [43]. Moreover, the BguR operator site that we proposed in this study is also similar to the predicted GmuR (5′-tAAATGTaTAGACAttTa-3′) operator site in the order of bacillales [44].…”

Section: Discussionsupporting

confidence: 71%

Cellobiose-Mediated Gene Expression in Streptococcus pneumoniae: A Repressor Function of the Novel GntR-Type Regulator BguR

2013

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The human pathogen Streptococcus pneumoniae has the ability to use the carbon- and energy source cellobiose due to the presence of a cellobiose-utilizing gene cluster (cel locus) in its genome. This system is regulated by the cellobiose-dependent transcriptional activator CelR, which has been previously shown to contribute to pneumococcal virulence. To get a broader understanding of the response of S. pneumoniae to cellobiose, we compared the pneumococcal transcriptome during growth on glucose as the main carbon source to that with cellobiose as the main carbon source. The expression of various carbon metabolic genes was altered, including a PTS operon (which we here denote as the bgu operon) that has high similarity with the cel locus. In contrast to the cel locus, the bgu operon is conserved in all sequenced strains of S. pneumoniae, indicating an important physiological function in the lifestyle of pneumococci. We next characterized the transcriptional regulation of the bgu operon in more detail. Its expression was increased in the presence of cellobiose, and decreased in the presence of glucose. A novel GntR-type transcriptional regulator (which we here denote as BguR) was shown to act as a transcriptional repressor of the bgu operon and its repressive effect was relieved in the presence of cellobiose. BguR-dependent repression was demonstrated to be mediated by a 20-bp DNA operator site (5′-AAAAATGTCTAGACAAATTT-3′) present in PbguA, as verified by promoter truncation experiments. In conclusion, we have identified a new cellobiose-responsive PTS operon, together with its transcriptional regulator in S. pneumoniae.

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Section: Discussionsupporting

confidence: 71%

Cellobiose-Mediated Gene Expression in Streptococcus pneumoniae: A Repressor Function of the Novel GntR-Type Regulator BguR

2013

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“…Presumably, these culture conditions still provide carbon sources sufficient for growth. In addition to K. pneumoniae, other members of the Enterobacteriaceae family, such as Aerobacter, Citrobacter, and Serratia, are able to utilize cellobiose and other ␤-glucosides (34). Most of these bacteria harbor several loci in common with the cellobiose-specific PTS, implying the ability to metabolize ␤-glucoside sugars (42).…”

Section: Discussionmentioning

confidence: 99%

Cellobiose-Specific Phosphotransferase System of Klebsiella pneumoniae and Its Importance in Biofilm Formation and Virulence

Chen

Lin

et al. 2012

Infect Immun

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ABSTRACTKlebsiella pneumoniaeis a Gram-negative bacillus belonging to the familyEnterobacteriaceae. In the past 20 years,K. pneumoniaehas become the predominant pathogen causing community-acquired pyogenic liver abscess (PLA). The formation of biofilm facilitates bacterial colonization and has been implicated in reduced susceptibility to the host immune response. To investigate genes related to biofilm formation in a PLA-associatedK. pneumoniaestrain, a transposon mutant library was screened by microtiter plate assay to identify isolates impaired for biofilm formation. One of the mutants was disrupted incelB, encoding the putative cellobiose-specific subunit IIC of enzyme II (EIIC) of a carbohydrate phosphotransferase system (PTS). This transmembrane protein is responsible for recognizing and binding specific sugars and transporting them across the cell membrane into the cytoplasm. Deletion and chromosomal complementation ofcelBconfirmed, by microtiter plate and slide culture assays, thatcelBwas indeed responsible for biofilm formation. Cellobiose-specific PTS activities of deletion mutants grown in LB broth and 0.005% cellobiose minimal medium were markedly lower than that of the wild-type strain grown under the same conditions, thereby confirming the involvement ofcelBin cellobiose transport. In 0.005% cellobiose minimal medium, thecelBmutant showed a delay in growth compared to the wild-type strain. In a mouse model of intragastric infection, deletion of thecelBgene increased the survival rate from 12.5% to 87.5%, which suggests that thecelBdeletion mutant also exhibited reduced virulence. Thus, thecelBlocus ofK. pneumoniae may contribute to biofilm formation and virulence through the metabolism of cellobiose.

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“…For instance, the genes for the activators BglG and ChbR (CelR) are organized within the respective target operons bglGFB (15,26,33,34) and chbBCARF (or celABCDF) (12,24,25,28). On the other hand, the genes for the regulators AscG and BgcR form single-gene operons, which are located next to the divergently transcribed target operons, namely, ascFB (11,12) and bgcEFIHA (19), respectively. The modes of action are also different for these regulators.…”

Section: Vol 191 2009 Regulation Of Propionate Operon By Ascg 6141mentioning

confidence: 99%

“…The chbR (celD) gene, encoding a repressor-activator dual regulator, is organized within this operon (11,12,25). A set of pathogenic E. coli strains carry an additional cryptic bgc operon encoding the enzymes for transport and hydrolysis of ␤-glucoside sugars (19). The divergently transcribed bgcR gene encodes a GntR-type transcription factor for positive control of the bgc operon.…”

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confidence: 99%

Participation of Regulator AscG of the β-Glucoside Utilization Operon in Regulation of the Propionate Catabolism Operon

2009

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The asc operon of Escherichia coli is one of the cryptic genetic systems for ␤-D-galactoside utilization as a carbon source. The ascFB genes for ␤-D-galactoside transport and catabolism are repressed by the AscG regulator. After genomic SELEX screening, AscG was found to recognize and bind the consensus palindromic sequence TGAAACC-GGTTTCA. AscG binding was detected at two sites upstream of the ascFB promoter and at three sites upstream of the prpBC operon for propionate catabolism. In an ascG-disrupted mutant, transcription of ascFB was enhanced, in agreement with the repressor model of AscG. This repression was indicated to be due to interference of binding of cyclic AMP-CRP to the CRP box, which overlaps with the AscG-binding site 1, as well as binding of RNA polymerase to the promoter. Under conditions of steady-state E. coli growth in a rich medium, the intracellular level of AscG stayed constant at a level supposedly leading to tight repression of the ascFB operon. The level of prpR, encoding the activator of prpBCDE, was also increased in the absence of AscG, indicating the involvement of AscG in repression of prpR. Taken together, these data suggest a metabolic link through interplay between the asc and prp operons.Both laboratory strains and natural isolates of Escherichia coli possess a number of cryptic genes for ␤-glucoside utilization (5). The most well-characterized bgl operon is the major genetic system for utilization of ␤-glucoside sugars such as arbutin and salicin. The bglGFB operon includes the genes encoding the enzymes for uptake of ␤-glucoside sugars and for hydrolysis of the phosphorylated substrates (15,26,33,34). BglG is a positive regulator of this bgl operon (26, 33) which prevents termination of transcription in the presence of ␤-glucosides. The bgl operon is, however, cryptic and uninducible in most E. coli strains under laboratory culture conditions (3, 23), but it is expressed and functional in some E. coli strains (5, 26, 31). The cryptic chbBCARF (or celABCDF) operon also includes the genes for transport and phosphorylation of cellobiose, arbutin, and salicin and for hydrolysis of phosphorylated substrates (11,12,24,28). The chbR (celD) gene, encoding a repressor-activator dual regulator, is organized within this operon (11,12,25). A set of pathogenic E. coli strains carry an additional cryptic bgc operon encoding the enzymes for transport and hydrolysis of ␤-glucoside sugars (19). The divergently transcribed bgcR gene encodes a GntR-type transcription factor for positive control of the bgc operon. The asc operon (arbutin-salicin-cellobiose) was discovered by selecting for cellobiose utilization in a bgl chb (or bgl cel) double mutant (4, 5, 23). The cryptic asc operon encodes a repressor (ascG), a phosphotransferase system enzyme II (ascF) for the transport of arbutin, salicin, and cellobiose, and a phospho-␤-glucosidase (ascB) that hydrolyzes the sugars which are phosphorylated during transport. The ascG and ascFB operons are transcribed from divergent promoters. The ascFB gen...

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Characterization of a β-Glucoside Operon (bgc) Prevalent in Septicemic and UropathogenicEscherichia coliStrains

Cited by 9 publications

References 39 publications

Cellobiose-Mediated Gene Expression in Streptococcus pneumoniae: A Repressor Function of the Novel GntR-Type Regulator BguR

Cellobiose-Mediated Gene Expression in Streptococcus pneumoniae: A Repressor Function of the Novel GntR-Type Regulator BguR

Cellobiose-Specific Phosphotransferase System of Klebsiella pneumoniae and Its Importance in Biofilm Formation and Virulence

Participation of Regulator AscG of the β-Glucoside Utilization Operon in Regulation of the Propionate Catabolism Operon

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