Search tips
Search criteria

Results 1-6 (6)

Clipboard (0)

Select a Filter Below

more »
Year of Publication
Document Types
1.  Cellodextrin Utilization by Bifidobacterium breve UCC2003▿ †  
Cellodextrins, the incomplete hydrolysis products from insoluble cellulose, are accessible as a carbon source to certain members of the human gut microbiota, such as Bifidobacterium breve UCC2003. Transcription of the cldEFGC gene cluster of B. breve UCC2003 was shown to be induced upon growth on cellodextrins, implicating this cluster in the metabolism of these sugars. Phenotypic analysis of a B. breve UCC2003::cldE insertion mutant confirmed that the cld gene cluster is exclusively required for cellodextrin utilization by this commensal. Moreover, our results suggest that transcription of the cld cluster is controlled by a LacI-type regulator encoded by cldR, located immediately upstream of cldE. Gel mobility shift assays using purified CldRHis (produced by the incorporation of a His12-encoding sequence into the 3′ end of the cldC gene) indicate that the cldEFGC promoter is subject to negative control by CldRHis, which binds to two inverted repeats. Analysis by high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) of medium samples obtained during growth of B. breve UCC2003 on a mixture of cellodextrins revealed its ability to utilize cellobiose, cellotriose, cellotetraose, and cellopentaose, with cellotriose apparently representing the preferred substrate. The cldC gene of the cld operon of B. breve UCC2003 is, to the best of our knowledge, the first described bifidobacterial β-glucosidase exhibiting hydrolytic activity toward various cellodextrins.
PMCID: PMC3067287  PMID: 21216899
2.  Statistical Methods for Comparative Phenomics Using High-Throughput Phenotype Microarrays* 
We propose statistical methods for comparing phenomics data generated by the Biolog Phenotype Microarray (PM) platform for high-throughput phenotyping. Instead of the routinely used visual inspection of data with no sound inferential basis, we develop two approaches. The first approach is based on quantifying the distance between mean or median curves from two treatments and then applying a permutation test; we also consider a permutation test applied to areas under mean curves. The second approach employs functional principal component analysis. Properties of the proposed methods are investigated on both simulated data and data sets from the PM platform.
PMCID: PMC2942029  PMID: 20865133
functional data analysis; principal components; permutation tests; phenotype microarrays; high-throughput phenotyping; phenomics; Biolog
3.  Carbohydrate metabolism in Bifidobacteria 
Genes & Nutrition  2011;6(3):285-306.
Members of the genus Bifidobacterium can be found as components of the gastrointestinal microbiota, and are believed to play an important role in maintaining and promoting human health by eliciting a number of beneficial properties. Bifidobacteria can utilize a diverse range of dietary carbohydrates that escape degradation in the upper parts of the intestine, many of which are plant-derived oligo- and polysaccharides. The gene content of a bifidobacterial genome reflects this apparent metabolic adaptation to a complex carbohydrate-rich gastrointestinal tract environment as it encodes a large number of predicted carbohydrate-modifying enzymes. Different bifidobacterial strains may possess different carbohydrate utilizing abilities, as established by a number of studies reviewed here. Carbohydrate-degrading activities described for bifidobacteria and their relevance to the deliberate enhancement of number and/or activity of bifidobacteria in the gut are also discussed in this review.
PMCID: PMC3145055  PMID: 21484167
Carbohydrate metabolism; Prebiotic; Probiotic; Carbohydrate; Bifidobacterial metabolism; Bifidobacterium breve UCC2003; Glycosyl hydrolases
4.  Ribose utilization by the human commensal Bifidobacterium breve UCC2003 
Microbial biotechnology  2010;3(3):311-323.
Growth of Bifidobacterium breve UCC2003 on ribose leads to the transcriptional induction of the rbsACBDK gene cluster. Generation and phenotypic analysis of an rbsA insertion mutant established that the rbs gene cluster is essential for ribose utilization, and that its transcription is likely regulated by a LacI‐type regulator encoded by rbsR, located immediately upstream of rbsA. Gel mobility shift assays using purified RbsRHis indicate that the promoter upstream of rbsABCDK is negatively controlled by RbsRHis binding to an 18 bp inverted repeat and that RbsRHis binding activity is modulated by d‐ribose. The rbsK gene of the rbs operon of B. breve UCC2003 was shown to specify a ribokinase (EC, which specifically directs its phosphorylating activity towards d‐ribose, converting this pentose sugar to ribose‐5‐phosphate.
PMCID: PMC3815373  PMID: 21255330
5.  Characterization of Two Novel α-Glucosidases from Bifidobacterium breve UCC2003▿ †  
Two α-glucosidase-encoding genes (agl1 and agl2) from Bifidobacterium breve UCC2003 were identified and characterized. Based on their similarity to characterized carbohydrate hydrolases, the Agl1 and Agl2 enzymes are both assigned to a subgroup of the glycosyl hydrolase family 13, the α-1,6-glucosidases (EC Recombinant Agl1 and Agl2 into which a His12 sequence was incorporated (Agl1His and Agl2His, respectively) exhibited hydrolytic activity towards panose, isomaltose, isomaltotriose, and four sucrose isomers—palatinose, trehalulose, turanose, and maltulose—while also degrading trehalose and, to a lesser extent, nigerose. The preferred substrates for both enzymes were panose, isomaltose, and trehalulose. Furthermore, the pH and temperature optima for both enzymes were determined, showing that Agl1His exhibits higher thermo and pH optima than Agl2His. The two purified α-1,6-glucosidases were also shown to have transglycosylation activity, synthesizing oligosaccharides from palatinose, trehalulose, trehalose, panose, and isomaltotriose.
PMCID: PMC2643558  PMID: 19114534
6.  Cryptic prophages help bacteria cope with adverse environments 
Nature Communications  2010;1:147-.
Phages are the most abundant entity in the biosphere and outnumber bacteria by a factor of 10. Phage DNA may also constitute 20% of bacterial genomes; however, its role is ill defined. Here, we explore the impact of cryptic prophages on cell physiology by precisely deleting all nine prophage elements (166 kbp) using Escherichia coli. We find that cryptic prophages contribute significantly to resistance to sub-lethal concentrations of quinolone and β-lactam antibiotics primarily through proteins that inhibit cell division (for example, KilR of rac and DicB of Qin). Moreover, the prophages are beneficial for withstanding osmotic, oxidative and acid stresses, for increasing growth, and for influencing biofilm formation. Prophage CPS-53 proteins YfdK, YfdO and YfdS enhanced resistance to oxidative stress, prophages e14, CPS-53 and CP4-57 increased resistance to acid, and e14 and rac proteins increased early biofilm formation. Therefore, cryptic prophages provide multiple benefits to the host for surviving adverse environmental conditions.
Up to 20% of bacterial genomes are made up of cryptic prophages, but their function is relatively unknown. In this study, the authors demonstrate that prophages influence the response of the host cell to stress and provide a competitive growth advantage in the presence of antibiotics.
PMCID: PMC3105296  PMID: 21266997

Results 1-6 (6)